Dopamine Negatively Regulates the NCA Ion Channels in C. elegans (original) (raw)
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Dopamine negatively modulates the NCA ion channels in C. elegans
PLoS genetics, 2017
The NALCN/NCA ion channel is a cation channel related to voltage-gated sodium and calcium channels. NALCN has been reported to be a sodium leak channel with a conserved role in establishing neuronal resting membrane potential, but its precise cellular role and regulation are unclear. The Caenorhabditis elegans orthologs of NALCN, NCA-1 and NCA-2, act in premotor interneurons to regulate motor circuit activity that sustains locomotion. Recently we found that NCA-1 and NCA-2 are activated by a signal transduction pathway acting downstream of the heterotrimeric G protein Gq and the small GTPase Rho. Through a forward genetic screen, here we identify the GPCR kinase GRK-2 as a new player affecting signaling through the Gq-Rho-NCA pathway. Using structure-function analysis, we find that the GPCR phosphorylation and membrane association domains of GRK-2 are required for its function. Genetic epistasis experiments suggest that GRK-2 acts on the D2-like dopamine receptor DOP-3 to inhibit Go...
Genetics, 2017
The heterotrimeric G protein Gq positively regulates neuronal activity and synaptic transmission. Previously, the Rho guanine nucleotide exchange factor Trio was identified as a direct effector of Gq that acts in parallel to the canonical Gq effector phospholipase C. Here, we examine how Trio and Rho act to stimulate neuronal activity downstream of Gq in the nematode Caenorhabditis elegans Through two forward genetic screens, we identify the cation channels NCA-1 and NCA-2, orthologs of mammalian NALCN, as downstream targets of the Gq-Rho pathway. By performing genetic epistasis analysis using dominant activating mutations and recessive loss-of-function mutations in the members of this pathway, we show that NCA-1 and NCA-2 act downstream of Gq in a linear pathway. Through cell-specific rescue experiments, we show that function of these channels in head acetylcholine neurons is sufficient for normal locomotion in C. elegans Our results suggest that NCA-1 and NCA-2 are physiologically...
Nature Communications, 2015
Persistent neural activity, a sustained circuit output that outlasts the stimuli, underlies shortterm or working memory, as well as various mental representations. Molecular mechanisms that underlie persistent activity are not well understood. Combining in situ whole-cell patch clamping and quantitative locomotion analyses, we show here that the Caenorhabditis elegans neuromuscular system exhibits persistent rhythmic activity, and such an activity contributes to the sustainability of basal locomotion, and the maintenance of acceleration after stimulation. The NALCN family sodium leak channel regulates the resting membrane potential and excitability of invertebrate and vertebrate neurons. Our molecular genetics and electrophysiology analyses show that the C. elegans NALCN, NCA, activates a premotor interneuron network to potentiate persistent motor circuit activity and to sustain C. elegans locomotion. Collectively, these results reveal a mechanism for, and physiological function of, persistent neural activity using a simple animal model, providing potential mechanistic clues for working memory in other systems.
The SEK-1 p38 MAP Kinase Pathway Modulates Gq Signaling in Caenorhabditis elegans
G3 (Bethesda, Md.), 2017
Gq is a heterotrimeric G protein that is widely expressed in neurons and regulates neuronal activity. To identify pathways regulating neuronal Gq signaling we performed a forward genetic screen in Caenorhabditis elegans for suppressors of activated Gq. One of the suppressors is an allele of sek-1, which encodes a mitogen-activated protein kinase kinase (MAPKK) in the p38 MAPK pathway. Here we show that sek-1 mutants have a slow locomotion rate and that sek-1 acts in acetylcholine neurons to modulate both locomotion rate and Gq signaling. Furthermore, we find that sek-1 acts in mature neurons to modulate locomotion. Using genetic and behavioral approaches we demonstrate that other components of the p38 MAPK pathway also play a positive role in modulating locomotion and Gq signaling. Finally, we find that mutants in the SEK-1 p38 MAPK pathway partially suppress an activated mutant of the sodium leak channel NCA-1/NALCN, a downstream target of Gq signaling. Our results suggest that the...
Mechanism of extrasynaptic dopamine signaling in Caenorhabditis elegans
Nature Neuroscience, 2004
Defects in dopamine signaling underlie schizophrenia 1 , drug addiction 2 and Parkinson disease 3 . The effects of dopamine are mediated by heterotrimeric G proteins, as all dopamine receptors identified are seven-transmembrane proteins of the G protein-coupled receptor family 4 . However, the identity of the physiologically relevant signaling molecules and pathways activated by these receptors is less clear.
Genetics, 2009
The nerve-cell cytoskeleton is essential for the regulation of intrinsic neuronal activity. For example, neuronal migration defects are associated with microtubule regulators, such as LIS1 and dynein, as well as with actin regulators, including Rac GTPases and integrins, and have been thought to underlie epileptic seizures in patients with cortical malformations. However, it is plausible that post-developmental functions of specific cytoskeletal regulators contribute to the more transient nature of aberrant neuronal activity and could be masked by developmental anomalies. Accordingly, our previous results have illuminated functional roles, distinct from developmental contributions, for Caenorhabditis elegans orthologs of LIS1 and dynein in GABAergic synaptic vesicle transport. Here, we report that C. elegans with function-altering mutations in canonical Rac GTPase-signaling-pathway members demonstrated a robust behavioral response to a GABA A receptor antagonist, pentylenetetrazole. Rac mutants also exhibited hypersensitivity to an acetylcholinesterase inhibitor, aldicarb, uncovering deficiencies in inhibitory neurotransmission. RNA interference targeting Rac hypomorphs revealed synergistic interactions between the dynein motor complex and some, but not all, members of Rac-signaling pathways. These genetic interactions are consistent with putative Rac-dependent regulation of actin and microtubule networks and suggest that some cytoskeletal regulators cooperate to uniquely govern neuronal synchrony through dynein-mediated GABAergic vesicle transport in C. elegans.
PLoS Biology, 2008
Voltage-gated cation channels regulate neuronal excitability through selective ion flux. NALCN, a member of a protein family that is structurally related to the a1 subunits of voltage-gated sodium/calcium channels, was recently shown to regulate the resting membrane potentials by mediating sodium leak and the firing of mouse neurons. We identified a role for the Caenorhabditis elegans NALCN homologues NCA-1 and NCA-2 in the propagation of neuronal activity from cell bodies to synapses. Loss of NCA activities leads to reduced synaptic transmission at neuromuscular junctions and frequent halting in locomotion. In vivo calcium imaging experiments further indicate that while calcium influx in the cell bodies of egg-laying motorneurons is unaffected by altered NCA activity, synaptic calcium transients are significantly reduced in nca loss-of-function mutants and increased in nca gain-of-function mutants. NCA-1 localizes along axons and is enriched at nonsynaptic regions. Its localization and function depend on UNC-79, and UNC-80, a novel conserved protein that is also enriched at nonsynaptic regions. We propose that NCA-1 and UNC-80 regulate neuronal activity at least in part by transmitting depolarization signals to synapses in C. elegans neurons. Citation: Yeh E, Ng S, Zhang M, Bouhours M, Wang Y, et al. (2008) A putative cation channel, NCA-1, and a novel protein, UNC-80, transmit neuronal activity in C. elegans. PLoS Biol 6(3): e55.
2009
3 ABSTRACT The nerve cell cytoskeleton is essential for regulation of intrinsic neuronal activity. For example, neuronal migration defects are associated with microtubule regulators, such as LIS1 and dynein, as well as actin regulators, including Rac GTPases and integrins, and have been thought to underlie epileptic seizures in patients with cortical malformations. However, it is plausible that post-developmental functions of specific cytoskeletal regulators contribute to the more transient nature of aberrant neuronal activity and could be masked by developmental anomalies. Accordingly, our previous results have illuminated functional roles, distinct from developmental contributions, for C. elegans orthologs of LIS1 and dynein in GABAergic synaptic vesicle transport. Here, we report that C. elegans with function-altering mutations in canonical Rac GTPase signaling pathway members demonstrated a robust behavioral response to a GABA A receptor antagonist, pentylenetetrazole (PTZ). Rac...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2003
The Caenorhabditis elegans unc-2 gene encodes a voltage-gated calcium channel alpha1 subunit structurally related to mammalian dihydropyridine-insensitive high-threshold channels. In the present paper we describe the characterization of seven alleles of unc-2. Using an unc-2 promoter-tagged green fluorescent protein construct, we show that unc-2 is primarily expressed in motor neurons, several subsets of sensory neurons, and the HSN and VC neurons that control egg laying. Examination of behavioral phenotypes, including defecation, thrashing, and sensitivities to aldicarb and nicotine suggests that UNC-2 acts presynaptically to mediate both cholinergic and GABAergic neurotransmission. Sequence analysis of the unc-2 alleles shows that e55, ra605, ra606, ra609, and ra610 all are predicted to prematurely terminate and greatly reduce or eliminate unc-2 function. In contrast, the ra612 and ra614 alleles are missense mutations resulting in the substitution of highly conserved residues in t...
Expression Profiling of GABAergic Motor Neurons in Caenorhabditis elegans
Current Biology, 2005
Neurons constitute the most diverse cell types and acquire their identity by the activity of particular genetic programs [1]. The GABAergic nervous system in C. elegans[2] consists of 26 neurons that fall into six classes 3 and 4. Animals that are defective in GABAergic neuron function and development display “shrinker” movement [5], abnormal foraging and defecation 4 and 6. Among the known shrinker genes, unc-25 and unc-47 encode the GABA biosynthetic enzyme glutamic acid decarboxylase and vesicular transporter, respectively 7 and 8. unc-30 encodes a homeodomain protein of the Pitx family and regulates the differentiation of the D-type GABAergic neurons [9]. unc-46 probably functions in presynaptic GABA release [6], but its identity has not been reported. By cell-based microarray analysis, we identified over 250 genes with enriched expression in GABAergic neurons. The highly enriched gene set included all known genes. In vivo expression study with computational predictions further identified six new genes that are potential transcriptional targets of UNC-30. Behavioral studies of a deletion mutant implicate a function of a nicotinic receptor subunit in D-type neurons. Our analysis demonstrates the utility of neuron-specific genomics in identifying cell-specific genes and regulatory networks.