Heleen Verlinden | KU Leuven (original) (raw)

Papers by Heleen Verlinden

Research paper thumbnail of Developmentaland food-dependent foraging transcript levels in the desert locust

Research paper thumbnail of The cloning, phylogenetic relationship and distribution pattern of two new putative GPCR-type octopamine receptors in the desert locust ( Schistocerca gregaria

Journal of Insect Physiology, 2010

Research paper thumbnail of RNA interference of insulin-related peptide and neuroparsins affects vitellogenesis in the desert locust Schistocerca gregaria

Peptides, 2011

The 'classic' insect hormones, juvenile hormone and 20-hydroxyecdysone, can stimulate vitellogene... more The 'classic' insect hormones, juvenile hormone and 20-hydroxyecdysone, can stimulate vitellogenesis and/or ovarian development in adult females of several insect species. Accumulating evidence also indicates a crucial role in female reproductive physiology for peptide hormones, such as insulin-related peptides (IRPs) and neuroparsins (NPs). Especially in dipteran species, IRP signaling has been shown to regulate female reproductive events. The first NP was originally identified from the migratory locust (Locusta migratoria) as an antigonadotropic factor that delayed vitellogenesis. Moreover, NP family members display sequence similarities with the N-terminal domain of vertebrate insulin-like growth factor binding proteins (IGFBPs). In the current study, RNA interference (RNAi) was employed to investigate the possible involvement of IRP and NPs in the control of the female desert locust (Schistocerca gregaria) reproductive system. The cDNAs encoding an IRP (Scg-IRP) and four NPs (Scg-NPs) had previously been cloned from S. gregaria. An RNAi-mediated knock-down of either Scg-NP or Scg-IRP transcript levels was induced in adult female desert locusts and the subsequent effects were analyzed. Knock-down of the Scg-NPs or Scg-IRP affected vitellogenin transcript levels and oocyte growth in a positive and negative way, respectively. The current findings are indicative for a role of Scg-NPs and Scg-IRP in the control of vitellogenin synthesis. A plausible hypothesis is that Scg-IRP may act as a sensor of the nutritional and metabolic status that determines whether vitellogenesis can occur. That the same processes were affected in opposite ways in both RNAi experiments offers an extra argument for antagonizing roles of Scg-NPs and Scg-IRP.

Research paper thumbnail of Critical role for PKA in the acquisition of gregarious behaviour in the Desert Locust

Proceedings of the National Academy of Sciences of the United States of America, 2013

Research paper thumbnail of The role of octopamine in locusts and other arthropods

Journal of Insect Physiology, 2010

Research paper thumbnail of Serotonin, serotonin receptors and their actions in insects

Serotonin is an ancient monoamine neurotransmitter, biochemically derived from tryptophan. It is ... more Serotonin is an ancient monoamine neurotransmitter, biochemically derived from tryptophan. It is most abundant in the gastrointestinal tract, but is also present throughout the rest of the body of animals and can even be found in plants and fungi. Serotonin is especially famous for its contributions to feelings of well-being and happiness. More specifically it is involved in learning and memory processes and is hence crucial for certain behaviors throughout the animal kingdom. This brief review will focus on the metabolism, biological role and mode-of-action of serotonin in insects. First, some general aspects of biosynthesis and break-down of serotonin in insects will be discussed, followed by an overview of the functions of serotonin, serotonin receptors and their pharmacology. Throughout this review comparisons are made with the vertebrate serotonergic system. Last but not least, possible applications of pharmacological adjustments of serotonin signaling in insects are discussed.

Research paper thumbnail of Chapter 6b Jozef Vanden Broeck FINAL VERSION

In metazoans, neuronal and endocrine communication is based on the release of extracellular signa... more In metazoans, neuronal and endocrine communication is based on the release of extracellular signaling molecules that are recognized in a physiological concentration range by specific receptor proteins present in the target cells. These receptors will elicit a cellular response upon activation by their physiological agonist. A highly diverse repertoire of naturally occurring receptor agonists has already been discovered. Peptides, proteins and biogenic amines constitute the most diverse agonist classes. Most of these interact with G protein-coupled receptors (GPCRs), the largest category of signal transducing receptors that controls virtually every physiological process in metazoans. For more than two decades, insect GPCRs have been hailed for their potentially excellent aptitude to serve as pharmacological targets for the development of novel products for insect pest control. In this review, we will address this issue and enumerate reasons why it would be worth investing more in these targets. -HT 5-hydroxytryptamine (serotonin) AKH adipokinetic hormone AR adrenergic receptor ARF ADP-ribosylation factor ARNO ARF nucleotide binding site opener AST allatostatin AT allatotropin ATL AT-like peptide ATR AT receptor BmNPV Bombyx mori nuclear polyhedrosis virus CA corpora allata CC corpora cardiaca CCAP crustacean cardioactive peptide CCK cholecystokinin CRF corticotrophin releasing factor CRF/DH CRF-like diuretic hormone CT/DH calcitonin-like diuretic hormone DLGR Drosophila melanogaster leucine-rich repeats containing GPCR E ecdysone ECL extracellular loop EH eclosion hormone ERK extracellular signal-regulated kinase ETH ecdysis-triggering hormone FOXO forkhead transcription factor GTPase activating protein GIT GRK-interacting protein GnRH gonadotropin-releasing hormone Grb2 growth factor receptor bound protein-2 GRK GPCR kinase ICL intracellular loop ILP insulin-like peptide InR insulin receptor IRP insulin-related peptide JH juvenile hormone MAPK mitogen-activated protein kinase MIP myoinhibiting peptide NPF neuropeptide F NPY neuropeptide Y NSF N-ethylmaleimide-sensitive fusion protein OMP ovary maturating parsin PBAN pheromone biosynthesis activating neuropeptide PDF pigment dispersing factor PDK1 3-phospoinositide-dependent protein kinase PI3K phosphoinositide 3-kinase PK pyrokinin PKA cAMP-dependent protein kinase PKB protein kinase B PKC Ca 2+ -dependent protein kinase PTEN phosphatase and tensin homolog PTTH prothoracicotropic hormone RPCH red pigment concentrating hormone

Research paper thumbnail of Peptidergic control of food intake and digestion in insects1

Canadian Journal of Zoology

Like all heterotrophic organisms, insects require a strict control of food intake and efficient d... more Like all heterotrophic organisms, insects require a strict control of food intake and efficient digestion of food into nutrients to maintain homeostasis and to fulfill physiological tasks. Feeding and digestion are steered by both external and internal signals that are transduced by a multitude of regulatory factors, delivered either by neurons innervating the gut or mouthparts, or by midgut endocrine cells. The present review gives an overview of peptide regulators known to control feeding and digestion in insects. We describe the discovery and functional role in these processes for insect allatoregulatory peptides, diuretic hormones, FMRFamide-related peptides, (short) neuropeptide F, proctolin, saliva production stimulating peptides, kinins, and tachykinins. These peptides control either gut myoactivity, food intake, and (or) release of digestive enzymes. Some peptides exert their action at multiple levels, possibly having a biological function that depends on their site of deliv...

Research paper thumbnail of The pleiotropic allatoregulatory neuropeptides and their receptors: A mini-review

Journal of Insect Physiology, 2015

Juvenile hormones (JH) are highly pleiotropic insect hormones essential for postembryonic develop... more Juvenile hormones (JH) are highly pleiotropic insect hormones essential for postembryonic development. The circulating JH titer in the haemolymph of insects is influenced by enzymatic degradation, binding to JH carrier proteins, uptake and storage in target organs, but evidently also by rates of production at its site of synthesis, the corpora allata (CA). The multiple processes in which JH is involved alongside the critical significance of JH in insect development emphasize the importance for elucidating the control of JH production. Production of JH in CA cells is regulated by different factors: by neurotransmitters, such as dopamine and glutamate, but also by allatoregulatory neuropeptides originating from the brain and axonally transported to the CA where they bind to their G proteincoupled receptors (GPCRs). Different classes of allatoregulatory peptides exist which have other functions aside from acting as influencers of JH production. These pleiotropic neuropeptides regulate different processes in different insect orders. In this mini-review, we will give an overview of allatotropins and allatostatins, and their recently characterized GPCRs with a view to better understand their modes of action and different action sites.

Research paper thumbnail of More than two decades of research on insect neuropeptide GPCRs: an overview

Frontiers in endocrinology, 2012

This review focuses on the state of the art on neuropeptide receptors in insects. Most of these r... more This review focuses on the state of the art on neuropeptide receptors in insects. Most of these receptors are G protein-coupled receptors (GPCRs) and are involved in the regulation of virtually all physiological processes during an insect's life. More than 20 years ago a milestone in invertebrate endocrinology was achieved with the characterization of the first insect neuropeptide receptor, i.e., the Drosophila tachykinin-like receptor. However, it took until the release of the Drosophila genome in 2000 that research on neuropeptide receptors boosted. In the last decade a plethora of genomic information of other insect species also became available, leading to a better insight in the functions and evolution of the neuropeptide signaling systems and their intracellular pathways. It became clear that some of these systems are conserved among all insect species, indicating that they fulfill crucial roles in their physiological processes. Meanwhile, other signaling systems seem to b...

Research paper thumbnail of Receptors for Neuronal or Endocrine Signalling Molecules as Potential Targets for the Control of Insect Pests

Advances in Insect Physiology, 2014

In metazoans, neuronal and endocrine communication is based on the release of extracellular signa... more In metazoans, neuronal and endocrine communication is based on the release of extracellular signaling molecules that are recognized in a physiological concentration range by specific receptor proteins present in the target cells. These receptors will elicit a cellular response upon activation by their physiological agonist. A highly diverse repertoire of naturally occurring receptor agonists has already been discovered. Peptides, proteins and biogenic amines constitute the most diverse agonist classes. Most of these interact with G protein-coupled receptors (GPCRs), the largest category of signal transducing receptors that controls virtually every physiological process in metazoans. For more than two decades, insect GPCRs have been hailed for their potentially excellent aptitude to serve as pharmacological targets for the development of novel products for insect pest control. In this review, we will address this issue and enumerate reasons why it would be worth investing more in these targets. -HT 5-hydroxytryptamine (serotonin) AKH adipokinetic hormone AR adrenergic receptor ARF ADP-ribosylation factor ARNO ARF nucleotide binding site opener AST allatostatin AT allatotropin ATL AT-like peptide ATR AT receptor BmNPV Bombyx mori nuclear polyhedrosis virus CA corpora allata CC corpora cardiaca CCAP crustacean cardioactive peptide CCK cholecystokinin CRF corticotrophin releasing factor CRF/DH CRF-like diuretic hormone CT/DH calcitonin-like diuretic hormone DLGR Drosophila melanogaster leucine-rich repeats containing GPCR E ecdysone ECL extracellular loop EH eclosion hormone ERK extracellular signal-regulated kinase ETH ecdysis-triggering hormone FOXO forkhead transcription factor GTPase activating protein GIT GRK-interacting protein GnRH gonadotropin-releasing hormone Grb2 growth factor receptor bound protein-2 GRK GPCR kinase ICL intracellular loop ILP insulin-like peptide InR insulin receptor IRP insulin-related peptide JH juvenile hormone MAPK mitogen-activated protein kinase MIP myoinhibiting peptide NPF neuropeptide F NPY neuropeptide Y NSF N-ethylmaleimide-sensitive fusion protein OMP ovary maturating parsin PBAN pheromone biosynthesis activating neuropeptide PDF pigment dispersing factor PDK1 3-phospoinositide-dependent protein kinase PI3K phosphoinositide 3-kinase PK pyrokinin PKA cAMP-dependent protein kinase PKB protein kinase B PKC Ca 2+ -dependent protein kinase PTEN phosphatase and tensin homolog PTTH prothoracicotropic hormone RPCH red pigment concentrating hormone

Research paper thumbnail of Functional Characterization of the Short Neuropeptide F Receptor in the Desert Locust, Schistocerca gregaria

PLoS ONE, 2013

Whereas short neuropeptide F (sNPF) has already been reported to stimulate feeding behaviour in a... more Whereas short neuropeptide F (sNPF) has already been reported to stimulate feeding behaviour in a variety of insect species, the opposite effect was observed in the desert locust. In the present study, we cloned a G protein-coupled receptor (GPCR) cDNA from the desert locust, Schistocerca gregaria. Cell-based functional analysis of this receptor indicated that it is activated by both known isoforms of Schgr-sNPF in a concentration dependent manner, with EC 50 values in the nanomolar range. This Schgr-sNPF receptor constitutes the first functionally characterized peptide GPCR in locusts. The in vivo effects of the sNPF signalling pathway on the regulation of feeding in locusts were further studied by knocking down the newly identified Schgr-sNPF receptor by means of RNA interference, as well as by means of peptide injection studies. While injection of sNPF caused an inhibitory effect on food uptake in the desert locust, knocking down the corresponding peptide receptor resulted in an increase of total food uptake when compared to control animals. This is the first comprehensive study in which a clearly negative correlation is described between the sNPF signalling pathway and feeding, prompting a reconsideration of the diverse roles of sNPFs in the physiology of insects.

Research paper thumbnail of Isolation and functional characterization of an allatotropin receptor from Manduca sexta

Insect Biochemistry and Molecular Biology, 2011

Manduca sexta allatotropin (Manse-AT) is a multifunctional neuropeptide whose actions include the... more Manduca sexta allatotropin (Manse-AT) is a multifunctional neuropeptide whose actions include the stimulation of juvenile hormone biosynthesis, myotropic stimulation, cardioacceleratory functions, and inhibition of active ion transport. Manse-AT is a member of a structurally related peptide family that is widely found in insects and also in other invertebrates. Its precise role depends on the insect species and developmental stage. In

Research paper thumbnail of Critical role for protein kinase A in the acquisition of gregarious behavior in the desert locust

Proceedings of the National Academy of Sciences, 2012

The mechanisms that integrate genetic and environmental information to coordinate the expression ... more The mechanisms that integrate genetic and environmental information to coordinate the expression of complex phenotypes are little understood. We investigated the role of two protein kinases (PKs) in the population density-dependent transition to gregarious behavior that underlies swarm formation in desert locusts: the foraging gene product, a cGMP-dependent PK (PKG) implicated in switching between alternative group-related behaviors in several animal species; and cAMP-dependent PK (PKA), a signal transduction protein with a preeminent role in different forms of learning. Solitarious locusts acquire key behavioral characters of the swarming gregarious phase within just 1 to 4 h of forced crowding. Injecting the PKA inhibitor KT5720 before crowding prevented this transition, whereas injecting KT5823, an inhibitor of PKG, did not. Neither drug altered the behavior of long-term gregarious locusts. RNAi against foraging effectively reduced its expression in the central nervous system, but this did not prevent gregarization upon crowding. By contrast, solitarious locusts with an RNAi-induced reduction in PKA catalytic subunit C1 expression behaved less gregariously after crowding, and RNAi against the inhibitory R1 subunit promoted more extensive gregarization following a brief crowding period. A central role of PKA is congruent with the recent discovery that serotonin mediates gregarization in locusts and with findings in vertebrates that similarly implicate PKA in the capacity to cope with adverse life events. Our results show that PKA has been coopted into effecting the wide-ranging transformation from solitarious to gregarious behavior, with PKAmediated behavioral plasticity resulting in an environmentally driven reorganization of a complex phenotype. phase change | phenotypic plasticity | Schistocerca gregaria H ow genetic information is integrated with environmental cues to control and coordinate complex phenotypes is a fundamental question in biology (1, 2). Environmental input can cause concerted changes in multiple traits to produce distinct phenotypic syndromes that are adaptive in particular conditions. Phase polyphenism in desert locusts (Schistocerca gregaria) is an extreme example. Locusts can reversibly transform between a solitarious phase and a gregarious phase that differ profoundly in morphology, physiology, and behavior (3-5). Solitarious locusts occur at low population densities and actively avoid conspecifics; they are cryptic in appearance and behavior; walk with a slow, creeping gait; and have restricted dietary preferences. The gregarious phase is characterized by increased activity and locomotion, an upright posture and gait, aposematic coloration, a broad dietary range, and, most critically, attraction to other locusts. Phase change is driven by huge changes in population density and is an adaptation to arid habitats where rains are infrequent and erratic. Transitory periods of verdure support rapid population growth, but after the rains cease, large numbers of solitarious locusts compete for dwindling patches of resources (6, 7). The resultant crowding causes a rapid transition to gregarious behavior by exposing solitarious locusts to specific sensory stimuli from conspecifics: repeated touch to the hind femur and the combination of visual and olfactory cues (8-10). Gre-garious behavior ensures further exposure to other locusts and thereby sets up a positive feedback loop that drives further phenotypic changes accruing over the locusts' lifetimes and even across generations. This behavior is also what makes locusts notorious pests, as highly mobile groups of gregarized locusts can further coalesce to escalate into enormous swarms that devastate crops and pastures.

Research paper thumbnail of Molecular cloning and characterization of an allergen from Persian melon*1

Journal of Allergy and Clinical Immunology, 2004

Profilin is a panallergen that is recognized by IgE from about 20% of birch pollen-and plant food... more Profilin is a panallergen that is recognized by IgE from about 20% of birch pollen-and plant food-allergic patients. Most of the melon-allergic patients (more than 70 percent) presented specific IgEantibodies to 14.4 Kda protein in melon extract that could be attributed to profilin. METHODS: To characterize allergenic component of the melon at the molecular level, this study was aimed at the cloning of melon major allergen cDNA. The IgE-binding component was isolated from melon by cation exchange FPLC and a purification step on poly-L-proline 4BSepharose. Cloning of melon profilin was performed by reverse transcription-PCR using degenerated primers. 5' and 3' RACE methods were carried out for the identification of the unknown 5'-end and 3'-end of the cDNA. RESULTS: Four isoforms of profilin identified that significant differences were noted in the non-coding regions, whereas coding sequence in one of them only showed a variation in position 54.Coding sequences of all isoforms (AY292385, AY292386, AY292385) had a length of 394 bp corresponding to 131 amino acid residues and a predicted isoelectric point of 4.46. The deduced amino acid sequence of the corresponding protein showed high identity with other plant profilins (71-84%) recently described as allergens. CONCLUSIONS: Profilin is an important allergenic compound in melon and shows high homology to pollens profilin. Pollenosis and associated allergies to melon can therefore partly be explained by the cross-reactivity between homologous profilins. Funding: Mashhad University of Medical Sciences, Indoor Biotechnologie J ALLERGY CLIN IMMUNOL Abstracts S299 VOLUME 113, NUMBER 2 TUESDAY

Research paper thumbnail of Developmental- and food-dependent foraging transcript levels in the desert locust

Insect Science, 2013

Drastic changes in the environment during a lifetime require developmental and physiological flex... more Drastic changes in the environment during a lifetime require developmental and physiological flexibility to ensure animal survival. Desert locusts, Schistocerca gregaria, live in an extremely changeable environment, which alternates between periods of rainfall and abundant food and periods of drought and starvation. In order to survive, locusts display an extreme form of phenotypic plasticity that allows them to rapidly cope with these changing conditions by converting from a cryptic solitarious phase to a swarming, voracious gregarious phase. To accomplish this, locusts possess different conserved mediators of phenotypic plasticity. Recently, attention has been drawn to the possible roles of protein kinases in this process. In addition to cyclic AMP-dependent protein kinase (PKA), also cyclic GMP-dependent protein kinase (PKG), which was shown to be involved in changes of food-related behavior in a variety of insects, has been associated with locust phenotypic plasticity. In this article, we study the transcript levels of the S. gregaria orthologue of the foraging gene that encodes a PKG in different food-related, developmental and crowding conditions. Transcript levels of the S. gregaria foraging orthologue are highest in different parts of the gut and differ between isolated and crowd-reared locusts. They change when the availability of food is altered, display a distinct pattern with higher levels after a moult and decrease with age during postembryonic development.

Research paper thumbnail of Signalling properties and pharmacology of a 5-HT 7 -type serotonin receptor from Tribolium castaneum

Insect Molecular Biology, 2014

Research paper thumbnail of Tissue-dependence and sensitivity of the systemic RNA interference response in the desert locust, Schistocerca gregaria

Insect Biochemistry and Molecular Biology, 2012

We report on a comprehensive study of the systemic RNAi-response in the desert locust, Schistocer... more We report on a comprehensive study of the systemic RNAi-response in the desert locust, Schistocerca gregaria. Upon intra-abdominal injection of dsRNA for two housekeeping genes (alpha-tubulin 1a and gapdh) in the range of pg amounts of dsRNA per mg tissue, a potent reduction of their corresponding mRNA was obtained. Moreover, the observed transcript knockdown significantly increased in at least a 10 days period and eventually resulted in high mortality upon silencing of the alpha-tubulin 1a gene. A more moderate RNAi-response was however observed in the reproductive systems. Analysis of the tissuedependent transcript level profile of several putative RNAi-genes indicated reduced levels of two genes, namely sg-dicer-2 and sg-argonaute-2, in the reproductive systems. By silencing these components, we confirmed their importance in the RNAi-process and suggest that their expression levels are determinant for tissue-dependent differences in the potency of RNAi in the desert locust.

Research paper thumbnail of Final steps in juvenile hormone biosynthesis in the desert locust, Schistocerca gregaria

Insect biochemistry and molecular biology, 2011

Two genes coding for enzymes previously reported to be involved in the final steps of juvenile ho... more Two genes coding for enzymes previously reported to be involved in the final steps of juvenile hormone (JH) biosynthesis in different insect species, were characterised in the desert locust, Schistocerca gregaria. Juvenile hormone acid O-methyltransferase (JHAMT) was previously described to catalyse the conversion of farnesoic acid (FA) and JH acid to their methyl esters, methyl farnesoate (MF) and JH respectively. A second gene, CYP15A1 was reported to encode a cytochrome P450 enzyme responsible for the epoxidation of MF to JH. Additionally, a third gene, FAMeT (originally reported to encode a farnesoic acid methyltransferase) was included in this study. Using q-RT-PCR, all three genes (JHAMT, CYP15A1 and FAMeT) were found to be primarily expressed in the CA of the desert locust, the main biosynthetic tissue of JH. An RNA interference approach was used to verify the orthologous function of these genes in S. gregaria. Knockdown of the three genes in adult animals followed by the rad...

Research paper thumbnail of Characterisation of a functional allatotropin receptor in the bumblebee, Bombus terrestris (Hymenoptera, Apidae)

General and Comparative Endocrinology, 2013

Allatotropins (ATs) are multifunctional neuropeptides initially isolated from the tobacco hornwor... more Allatotropins (ATs) are multifunctional neuropeptides initially isolated from the tobacco hornworm, Manduca sexta, where they were found to stimulate juvenile hormone synthesis and release from the corpora allata. ATs have been found in a wide range of insects, but appear to be absent in Drosophila. The first AT receptor (ATR) was characterised in 2008 in the lepidopteran Bombyx mori. Since then ATRs have been characterised in Coleoptera and Diptera and in 2012, an AT precursor gene was identified in hymenopteran species. ATRs show large sequence and structural similarity to vertebrate orexin receptors (OXR). Also, AT in insects and orexin in vertebrates show some overlap in functions, including modulation of feeding behaviour and reproduction.

Research paper thumbnail of Developmentaland food-dependent foraging transcript levels in the desert locust

Research paper thumbnail of The cloning, phylogenetic relationship and distribution pattern of two new putative GPCR-type octopamine receptors in the desert locust ( Schistocerca gregaria

Journal of Insect Physiology, 2010

Research paper thumbnail of RNA interference of insulin-related peptide and neuroparsins affects vitellogenesis in the desert locust Schistocerca gregaria

Peptides, 2011

The 'classic' insect hormones, juvenile hormone and 20-hydroxyecdysone, can stimulate vitellogene... more The 'classic' insect hormones, juvenile hormone and 20-hydroxyecdysone, can stimulate vitellogenesis and/or ovarian development in adult females of several insect species. Accumulating evidence also indicates a crucial role in female reproductive physiology for peptide hormones, such as insulin-related peptides (IRPs) and neuroparsins (NPs). Especially in dipteran species, IRP signaling has been shown to regulate female reproductive events. The first NP was originally identified from the migratory locust (Locusta migratoria) as an antigonadotropic factor that delayed vitellogenesis. Moreover, NP family members display sequence similarities with the N-terminal domain of vertebrate insulin-like growth factor binding proteins (IGFBPs). In the current study, RNA interference (RNAi) was employed to investigate the possible involvement of IRP and NPs in the control of the female desert locust (Schistocerca gregaria) reproductive system. The cDNAs encoding an IRP (Scg-IRP) and four NPs (Scg-NPs) had previously been cloned from S. gregaria. An RNAi-mediated knock-down of either Scg-NP or Scg-IRP transcript levels was induced in adult female desert locusts and the subsequent effects were analyzed. Knock-down of the Scg-NPs or Scg-IRP affected vitellogenin transcript levels and oocyte growth in a positive and negative way, respectively. The current findings are indicative for a role of Scg-NPs and Scg-IRP in the control of vitellogenin synthesis. A plausible hypothesis is that Scg-IRP may act as a sensor of the nutritional and metabolic status that determines whether vitellogenesis can occur. That the same processes were affected in opposite ways in both RNAi experiments offers an extra argument for antagonizing roles of Scg-NPs and Scg-IRP.

Research paper thumbnail of Critical role for PKA in the acquisition of gregarious behaviour in the Desert Locust

Proceedings of the National Academy of Sciences of the United States of America, 2013

Research paper thumbnail of The role of octopamine in locusts and other arthropods

Journal of Insect Physiology, 2010

Research paper thumbnail of Serotonin, serotonin receptors and their actions in insects

Serotonin is an ancient monoamine neurotransmitter, biochemically derived from tryptophan. It is ... more Serotonin is an ancient monoamine neurotransmitter, biochemically derived from tryptophan. It is most abundant in the gastrointestinal tract, but is also present throughout the rest of the body of animals and can even be found in plants and fungi. Serotonin is especially famous for its contributions to feelings of well-being and happiness. More specifically it is involved in learning and memory processes and is hence crucial for certain behaviors throughout the animal kingdom. This brief review will focus on the metabolism, biological role and mode-of-action of serotonin in insects. First, some general aspects of biosynthesis and break-down of serotonin in insects will be discussed, followed by an overview of the functions of serotonin, serotonin receptors and their pharmacology. Throughout this review comparisons are made with the vertebrate serotonergic system. Last but not least, possible applications of pharmacological adjustments of serotonin signaling in insects are discussed.

Research paper thumbnail of Chapter 6b Jozef Vanden Broeck FINAL VERSION

In metazoans, neuronal and endocrine communication is based on the release of extracellular signa... more In metazoans, neuronal and endocrine communication is based on the release of extracellular signaling molecules that are recognized in a physiological concentration range by specific receptor proteins present in the target cells. These receptors will elicit a cellular response upon activation by their physiological agonist. A highly diverse repertoire of naturally occurring receptor agonists has already been discovered. Peptides, proteins and biogenic amines constitute the most diverse agonist classes. Most of these interact with G protein-coupled receptors (GPCRs), the largest category of signal transducing receptors that controls virtually every physiological process in metazoans. For more than two decades, insect GPCRs have been hailed for their potentially excellent aptitude to serve as pharmacological targets for the development of novel products for insect pest control. In this review, we will address this issue and enumerate reasons why it would be worth investing more in these targets. -HT 5-hydroxytryptamine (serotonin) AKH adipokinetic hormone AR adrenergic receptor ARF ADP-ribosylation factor ARNO ARF nucleotide binding site opener AST allatostatin AT allatotropin ATL AT-like peptide ATR AT receptor BmNPV Bombyx mori nuclear polyhedrosis virus CA corpora allata CC corpora cardiaca CCAP crustacean cardioactive peptide CCK cholecystokinin CRF corticotrophin releasing factor CRF/DH CRF-like diuretic hormone CT/DH calcitonin-like diuretic hormone DLGR Drosophila melanogaster leucine-rich repeats containing GPCR E ecdysone ECL extracellular loop EH eclosion hormone ERK extracellular signal-regulated kinase ETH ecdysis-triggering hormone FOXO forkhead transcription factor GTPase activating protein GIT GRK-interacting protein GnRH gonadotropin-releasing hormone Grb2 growth factor receptor bound protein-2 GRK GPCR kinase ICL intracellular loop ILP insulin-like peptide InR insulin receptor IRP insulin-related peptide JH juvenile hormone MAPK mitogen-activated protein kinase MIP myoinhibiting peptide NPF neuropeptide F NPY neuropeptide Y NSF N-ethylmaleimide-sensitive fusion protein OMP ovary maturating parsin PBAN pheromone biosynthesis activating neuropeptide PDF pigment dispersing factor PDK1 3-phospoinositide-dependent protein kinase PI3K phosphoinositide 3-kinase PK pyrokinin PKA cAMP-dependent protein kinase PKB protein kinase B PKC Ca 2+ -dependent protein kinase PTEN phosphatase and tensin homolog PTTH prothoracicotropic hormone RPCH red pigment concentrating hormone

Research paper thumbnail of Peptidergic control of food intake and digestion in insects1

Canadian Journal of Zoology

Like all heterotrophic organisms, insects require a strict control of food intake and efficient d... more Like all heterotrophic organisms, insects require a strict control of food intake and efficient digestion of food into nutrients to maintain homeostasis and to fulfill physiological tasks. Feeding and digestion are steered by both external and internal signals that are transduced by a multitude of regulatory factors, delivered either by neurons innervating the gut or mouthparts, or by midgut endocrine cells. The present review gives an overview of peptide regulators known to control feeding and digestion in insects. We describe the discovery and functional role in these processes for insect allatoregulatory peptides, diuretic hormones, FMRFamide-related peptides, (short) neuropeptide F, proctolin, saliva production stimulating peptides, kinins, and tachykinins. These peptides control either gut myoactivity, food intake, and (or) release of digestive enzymes. Some peptides exert their action at multiple levels, possibly having a biological function that depends on their site of deliv...

Research paper thumbnail of The pleiotropic allatoregulatory neuropeptides and their receptors: A mini-review

Journal of Insect Physiology, 2015

Juvenile hormones (JH) are highly pleiotropic insect hormones essential for postembryonic develop... more Juvenile hormones (JH) are highly pleiotropic insect hormones essential for postembryonic development. The circulating JH titer in the haemolymph of insects is influenced by enzymatic degradation, binding to JH carrier proteins, uptake and storage in target organs, but evidently also by rates of production at its site of synthesis, the corpora allata (CA). The multiple processes in which JH is involved alongside the critical significance of JH in insect development emphasize the importance for elucidating the control of JH production. Production of JH in CA cells is regulated by different factors: by neurotransmitters, such as dopamine and glutamate, but also by allatoregulatory neuropeptides originating from the brain and axonally transported to the CA where they bind to their G proteincoupled receptors (GPCRs). Different classes of allatoregulatory peptides exist which have other functions aside from acting as influencers of JH production. These pleiotropic neuropeptides regulate different processes in different insect orders. In this mini-review, we will give an overview of allatotropins and allatostatins, and their recently characterized GPCRs with a view to better understand their modes of action and different action sites.

Research paper thumbnail of More than two decades of research on insect neuropeptide GPCRs: an overview

Frontiers in endocrinology, 2012

This review focuses on the state of the art on neuropeptide receptors in insects. Most of these r... more This review focuses on the state of the art on neuropeptide receptors in insects. Most of these receptors are G protein-coupled receptors (GPCRs) and are involved in the regulation of virtually all physiological processes during an insect's life. More than 20 years ago a milestone in invertebrate endocrinology was achieved with the characterization of the first insect neuropeptide receptor, i.e., the Drosophila tachykinin-like receptor. However, it took until the release of the Drosophila genome in 2000 that research on neuropeptide receptors boosted. In the last decade a plethora of genomic information of other insect species also became available, leading to a better insight in the functions and evolution of the neuropeptide signaling systems and their intracellular pathways. It became clear that some of these systems are conserved among all insect species, indicating that they fulfill crucial roles in their physiological processes. Meanwhile, other signaling systems seem to b...

Research paper thumbnail of Receptors for Neuronal or Endocrine Signalling Molecules as Potential Targets for the Control of Insect Pests

Advances in Insect Physiology, 2014

In metazoans, neuronal and endocrine communication is based on the release of extracellular signa... more In metazoans, neuronal and endocrine communication is based on the release of extracellular signaling molecules that are recognized in a physiological concentration range by specific receptor proteins present in the target cells. These receptors will elicit a cellular response upon activation by their physiological agonist. A highly diverse repertoire of naturally occurring receptor agonists has already been discovered. Peptides, proteins and biogenic amines constitute the most diverse agonist classes. Most of these interact with G protein-coupled receptors (GPCRs), the largest category of signal transducing receptors that controls virtually every physiological process in metazoans. For more than two decades, insect GPCRs have been hailed for their potentially excellent aptitude to serve as pharmacological targets for the development of novel products for insect pest control. In this review, we will address this issue and enumerate reasons why it would be worth investing more in these targets. -HT 5-hydroxytryptamine (serotonin) AKH adipokinetic hormone AR adrenergic receptor ARF ADP-ribosylation factor ARNO ARF nucleotide binding site opener AST allatostatin AT allatotropin ATL AT-like peptide ATR AT receptor BmNPV Bombyx mori nuclear polyhedrosis virus CA corpora allata CC corpora cardiaca CCAP crustacean cardioactive peptide CCK cholecystokinin CRF corticotrophin releasing factor CRF/DH CRF-like diuretic hormone CT/DH calcitonin-like diuretic hormone DLGR Drosophila melanogaster leucine-rich repeats containing GPCR E ecdysone ECL extracellular loop EH eclosion hormone ERK extracellular signal-regulated kinase ETH ecdysis-triggering hormone FOXO forkhead transcription factor GTPase activating protein GIT GRK-interacting protein GnRH gonadotropin-releasing hormone Grb2 growth factor receptor bound protein-2 GRK GPCR kinase ICL intracellular loop ILP insulin-like peptide InR insulin receptor IRP insulin-related peptide JH juvenile hormone MAPK mitogen-activated protein kinase MIP myoinhibiting peptide NPF neuropeptide F NPY neuropeptide Y NSF N-ethylmaleimide-sensitive fusion protein OMP ovary maturating parsin PBAN pheromone biosynthesis activating neuropeptide PDF pigment dispersing factor PDK1 3-phospoinositide-dependent protein kinase PI3K phosphoinositide 3-kinase PK pyrokinin PKA cAMP-dependent protein kinase PKB protein kinase B PKC Ca 2+ -dependent protein kinase PTEN phosphatase and tensin homolog PTTH prothoracicotropic hormone RPCH red pigment concentrating hormone

Research paper thumbnail of Functional Characterization of the Short Neuropeptide F Receptor in the Desert Locust, Schistocerca gregaria

PLoS ONE, 2013

Whereas short neuropeptide F (sNPF) has already been reported to stimulate feeding behaviour in a... more Whereas short neuropeptide F (sNPF) has already been reported to stimulate feeding behaviour in a variety of insect species, the opposite effect was observed in the desert locust. In the present study, we cloned a G protein-coupled receptor (GPCR) cDNA from the desert locust, Schistocerca gregaria. Cell-based functional analysis of this receptor indicated that it is activated by both known isoforms of Schgr-sNPF in a concentration dependent manner, with EC 50 values in the nanomolar range. This Schgr-sNPF receptor constitutes the first functionally characterized peptide GPCR in locusts. The in vivo effects of the sNPF signalling pathway on the regulation of feeding in locusts were further studied by knocking down the newly identified Schgr-sNPF receptor by means of RNA interference, as well as by means of peptide injection studies. While injection of sNPF caused an inhibitory effect on food uptake in the desert locust, knocking down the corresponding peptide receptor resulted in an increase of total food uptake when compared to control animals. This is the first comprehensive study in which a clearly negative correlation is described between the sNPF signalling pathway and feeding, prompting a reconsideration of the diverse roles of sNPFs in the physiology of insects.

Research paper thumbnail of Isolation and functional characterization of an allatotropin receptor from Manduca sexta

Insect Biochemistry and Molecular Biology, 2011

Manduca sexta allatotropin (Manse-AT) is a multifunctional neuropeptide whose actions include the... more Manduca sexta allatotropin (Manse-AT) is a multifunctional neuropeptide whose actions include the stimulation of juvenile hormone biosynthesis, myotropic stimulation, cardioacceleratory functions, and inhibition of active ion transport. Manse-AT is a member of a structurally related peptide family that is widely found in insects and also in other invertebrates. Its precise role depends on the insect species and developmental stage. In

Research paper thumbnail of Critical role for protein kinase A in the acquisition of gregarious behavior in the desert locust

Proceedings of the National Academy of Sciences, 2012

The mechanisms that integrate genetic and environmental information to coordinate the expression ... more The mechanisms that integrate genetic and environmental information to coordinate the expression of complex phenotypes are little understood. We investigated the role of two protein kinases (PKs) in the population density-dependent transition to gregarious behavior that underlies swarm formation in desert locusts: the foraging gene product, a cGMP-dependent PK (PKG) implicated in switching between alternative group-related behaviors in several animal species; and cAMP-dependent PK (PKA), a signal transduction protein with a preeminent role in different forms of learning. Solitarious locusts acquire key behavioral characters of the swarming gregarious phase within just 1 to 4 h of forced crowding. Injecting the PKA inhibitor KT5720 before crowding prevented this transition, whereas injecting KT5823, an inhibitor of PKG, did not. Neither drug altered the behavior of long-term gregarious locusts. RNAi against foraging effectively reduced its expression in the central nervous system, but this did not prevent gregarization upon crowding. By contrast, solitarious locusts with an RNAi-induced reduction in PKA catalytic subunit C1 expression behaved less gregariously after crowding, and RNAi against the inhibitory R1 subunit promoted more extensive gregarization following a brief crowding period. A central role of PKA is congruent with the recent discovery that serotonin mediates gregarization in locusts and with findings in vertebrates that similarly implicate PKA in the capacity to cope with adverse life events. Our results show that PKA has been coopted into effecting the wide-ranging transformation from solitarious to gregarious behavior, with PKAmediated behavioral plasticity resulting in an environmentally driven reorganization of a complex phenotype. phase change | phenotypic plasticity | Schistocerca gregaria H ow genetic information is integrated with environmental cues to control and coordinate complex phenotypes is a fundamental question in biology (1, 2). Environmental input can cause concerted changes in multiple traits to produce distinct phenotypic syndromes that are adaptive in particular conditions. Phase polyphenism in desert locusts (Schistocerca gregaria) is an extreme example. Locusts can reversibly transform between a solitarious phase and a gregarious phase that differ profoundly in morphology, physiology, and behavior (3-5). Solitarious locusts occur at low population densities and actively avoid conspecifics; they are cryptic in appearance and behavior; walk with a slow, creeping gait; and have restricted dietary preferences. The gregarious phase is characterized by increased activity and locomotion, an upright posture and gait, aposematic coloration, a broad dietary range, and, most critically, attraction to other locusts. Phase change is driven by huge changes in population density and is an adaptation to arid habitats where rains are infrequent and erratic. Transitory periods of verdure support rapid population growth, but after the rains cease, large numbers of solitarious locusts compete for dwindling patches of resources (6, 7). The resultant crowding causes a rapid transition to gregarious behavior by exposing solitarious locusts to specific sensory stimuli from conspecifics: repeated touch to the hind femur and the combination of visual and olfactory cues (8-10). Gre-garious behavior ensures further exposure to other locusts and thereby sets up a positive feedback loop that drives further phenotypic changes accruing over the locusts' lifetimes and even across generations. This behavior is also what makes locusts notorious pests, as highly mobile groups of gregarized locusts can further coalesce to escalate into enormous swarms that devastate crops and pastures.

Research paper thumbnail of Molecular cloning and characterization of an allergen from Persian melon*1

Journal of Allergy and Clinical Immunology, 2004

Profilin is a panallergen that is recognized by IgE from about 20% of birch pollen-and plant food... more Profilin is a panallergen that is recognized by IgE from about 20% of birch pollen-and plant food-allergic patients. Most of the melon-allergic patients (more than 70 percent) presented specific IgEantibodies to 14.4 Kda protein in melon extract that could be attributed to profilin. METHODS: To characterize allergenic component of the melon at the molecular level, this study was aimed at the cloning of melon major allergen cDNA. The IgE-binding component was isolated from melon by cation exchange FPLC and a purification step on poly-L-proline 4BSepharose. Cloning of melon profilin was performed by reverse transcription-PCR using degenerated primers. 5' and 3' RACE methods were carried out for the identification of the unknown 5'-end and 3'-end of the cDNA. RESULTS: Four isoforms of profilin identified that significant differences were noted in the non-coding regions, whereas coding sequence in one of them only showed a variation in position 54.Coding sequences of all isoforms (AY292385, AY292386, AY292385) had a length of 394 bp corresponding to 131 amino acid residues and a predicted isoelectric point of 4.46. The deduced amino acid sequence of the corresponding protein showed high identity with other plant profilins (71-84%) recently described as allergens. CONCLUSIONS: Profilin is an important allergenic compound in melon and shows high homology to pollens profilin. Pollenosis and associated allergies to melon can therefore partly be explained by the cross-reactivity between homologous profilins. Funding: Mashhad University of Medical Sciences, Indoor Biotechnologie J ALLERGY CLIN IMMUNOL Abstracts S299 VOLUME 113, NUMBER 2 TUESDAY

Research paper thumbnail of Developmental- and food-dependent foraging transcript levels in the desert locust

Insect Science, 2013

Drastic changes in the environment during a lifetime require developmental and physiological flex... more Drastic changes in the environment during a lifetime require developmental and physiological flexibility to ensure animal survival. Desert locusts, Schistocerca gregaria, live in an extremely changeable environment, which alternates between periods of rainfall and abundant food and periods of drought and starvation. In order to survive, locusts display an extreme form of phenotypic plasticity that allows them to rapidly cope with these changing conditions by converting from a cryptic solitarious phase to a swarming, voracious gregarious phase. To accomplish this, locusts possess different conserved mediators of phenotypic plasticity. Recently, attention has been drawn to the possible roles of protein kinases in this process. In addition to cyclic AMP-dependent protein kinase (PKA), also cyclic GMP-dependent protein kinase (PKG), which was shown to be involved in changes of food-related behavior in a variety of insects, has been associated with locust phenotypic plasticity. In this article, we study the transcript levels of the S. gregaria orthologue of the foraging gene that encodes a PKG in different food-related, developmental and crowding conditions. Transcript levels of the S. gregaria foraging orthologue are highest in different parts of the gut and differ between isolated and crowd-reared locusts. They change when the availability of food is altered, display a distinct pattern with higher levels after a moult and decrease with age during postembryonic development.

Research paper thumbnail of Signalling properties and pharmacology of a 5-HT 7 -type serotonin receptor from Tribolium castaneum

Insect Molecular Biology, 2014

Research paper thumbnail of Tissue-dependence and sensitivity of the systemic RNA interference response in the desert locust, Schistocerca gregaria

Insect Biochemistry and Molecular Biology, 2012

We report on a comprehensive study of the systemic RNAi-response in the desert locust, Schistocer... more We report on a comprehensive study of the systemic RNAi-response in the desert locust, Schistocerca gregaria. Upon intra-abdominal injection of dsRNA for two housekeeping genes (alpha-tubulin 1a and gapdh) in the range of pg amounts of dsRNA per mg tissue, a potent reduction of their corresponding mRNA was obtained. Moreover, the observed transcript knockdown significantly increased in at least a 10 days period and eventually resulted in high mortality upon silencing of the alpha-tubulin 1a gene. A more moderate RNAi-response was however observed in the reproductive systems. Analysis of the tissuedependent transcript level profile of several putative RNAi-genes indicated reduced levels of two genes, namely sg-dicer-2 and sg-argonaute-2, in the reproductive systems. By silencing these components, we confirmed their importance in the RNAi-process and suggest that their expression levels are determinant for tissue-dependent differences in the potency of RNAi in the desert locust.

Research paper thumbnail of Final steps in juvenile hormone biosynthesis in the desert locust, Schistocerca gregaria

Insect biochemistry and molecular biology, 2011

Two genes coding for enzymes previously reported to be involved in the final steps of juvenile ho... more Two genes coding for enzymes previously reported to be involved in the final steps of juvenile hormone (JH) biosynthesis in different insect species, were characterised in the desert locust, Schistocerca gregaria. Juvenile hormone acid O-methyltransferase (JHAMT) was previously described to catalyse the conversion of farnesoic acid (FA) and JH acid to their methyl esters, methyl farnesoate (MF) and JH respectively. A second gene, CYP15A1 was reported to encode a cytochrome P450 enzyme responsible for the epoxidation of MF to JH. Additionally, a third gene, FAMeT (originally reported to encode a farnesoic acid methyltransferase) was included in this study. Using q-RT-PCR, all three genes (JHAMT, CYP15A1 and FAMeT) were found to be primarily expressed in the CA of the desert locust, the main biosynthetic tissue of JH. An RNA interference approach was used to verify the orthologous function of these genes in S. gregaria. Knockdown of the three genes in adult animals followed by the rad...

Research paper thumbnail of Characterisation of a functional allatotropin receptor in the bumblebee, Bombus terrestris (Hymenoptera, Apidae)

General and Comparative Endocrinology, 2013

Allatotropins (ATs) are multifunctional neuropeptides initially isolated from the tobacco hornwor... more Allatotropins (ATs) are multifunctional neuropeptides initially isolated from the tobacco hornworm, Manduca sexta, where they were found to stimulate juvenile hormone synthesis and release from the corpora allata. ATs have been found in a wide range of insects, but appear to be absent in Drosophila. The first AT receptor (ATR) was characterised in 2008 in the lepidopteran Bombyx mori. Since then ATRs have been characterised in Coleoptera and Diptera and in 2012, an AT precursor gene was identified in hymenopteran species. ATRs show large sequence and structural similarity to vertebrate orexin receptors (OXR). Also, AT in insects and orexin in vertebrates show some overlap in functions, including modulation of feeding behaviour and reproduction.