Gunnar Keppler Gouras | Lund University (original) (raw)

Papers by Gunnar Keppler Gouras

Research paper thumbnail of Alzheimer β-amyloid peptides: Normal and abnormal localization

Histology and histopathology

Alzheimer's disease (AD) neuropathology is characterized by accumulation of "senile" plaques (SPs... more Alzheimer's disease (AD) neuropathology is characterized by accumulation of "senile" plaques (SPs) and neurofibrillary tangles (NFTs) in vulnerable brain regions. SPs are principally composed of aggregates of up to 42/43 amino acid ß-amyloid (Aß) peptides. The discovery of familial AD (FAD) mutations in the genes for the amyloid precursor protein (APP) and presenilins (PSs), all of which increase Aß42 production, support the view that Aß is centrally involved in the pathogenesis of AD. Aß42 aggregates readily, and is thought to seed the formation of fibrils, which then act as templates for plaque formation. Aß is generated by the sequential intracellular cleavage of APP by ßsecretase to generate the N-terminal end of Aß, and intramembranous cleavage by γ-secretase to generate the C-terminal end. Cell biological studies have demonstrated that Aß is generated in the ER, Golgi, and endosomal/lysosomal system. A central question involving the role of Aß in AD concerns how Aß causes disease and whether it is extracellular Aß deposition and/or intracellular Aß accumulation that initiates the disease process. The most prevalent view is that SPs are composed of extracellular deposits of secreted Aß and that Aß causes toxicity to surrounding neurons as extracellular SP. The recent emphasis on the intracellular biology of APP and Aß has led some investigators to consider the possibility that intraneuronal Aß may directly cause toxicity. In this review we will outline current knowledge of the localization of both intracellular and extracellular Aß.

Research paper thumbnail of Cellular and molecular basis of beta-amyloid precursor protein metabolism

Research paper thumbnail of ADAM10 and BACE1 are localized to synaptic vesicles

Journal of neurochemistry, Jan 22, 2015

Synaptic degeneration and accumulation of the neurotoxic amyloid β-peptide (Aβ) in the brain are ... more Synaptic degeneration and accumulation of the neurotoxic amyloid β-peptide (Aβ) in the brain are hallmarks of Alzheimer disease. Aβ is produced by sequential cleavage of its precursor protein, APP, by the β-secretase BACE1 and γ-secretase. However, Aβ generation is precluded if APP is cleaved by the α-secretase ADAM10 instead of BACE1. We have previously shown that Aβ can be produced locally at the synapse. To study the synaptic localization of the APP processing enzymes we used western blotting to demonstrate that, compared to total brain homogenate, ADAM10 and BACE1 were greatly enriched in synaptic vesicles isolated from rat brain using controlled-pore glass chromatography, whereas Presenilin1 was the only enriched component of the γ-secretase complex. Moreover, we detected ADAM10 activity in synaptic vesicles and enrichment of the intermediate APP-C-terminal fractions (APP-CTFs). We confirmed the western blotting findings using in situ proximity ligation assay to demonstrate clo...

Research paper thumbnail of Testosterone reduces neuronal secretion of Alzheimer's -amyloid peptides

Proceedings of the National Academy of Sciences

Alzheimer's disease (AD) is characterized by the age-related deposition of beta-amyloid (... more Alzheimer's disease (AD) is characterized by the age-related deposition of beta-amyloid (Abeta) 40/42 peptide aggregates in vulnerable brain regions. Multiple levels of evidence implicate a central role for Abeta in the pathophysiology of AD. Abeta peptides are generated by the regulated cleavage of an approximately 700-aa Abeta precursor protein (betaAPP). Full-length betaAPP can undergo proteolytic cleavage either within the Abeta domain to generate secreted sbetaAPPalpha or at the N- and C-terminal domain(s) of Abeta to generate amyloidogenic Abeta peptides. Several epidemiological studies have reported that estrogen replacement therapy protects against the development of AD in postmenopausal women. We previously reported that treating cultured neurons with 17beta-estradiol reduced the secretion of Abeta40/42 peptides, suggesting that estrogen replacement therapy may protect women against the development of AD by regulating betaAPP metabolism. Increasing evidence indicates that testosterone, especially bioavailable testosterone, decreases with age in older men and in postmenopausal women. We report here that treatment with testosterone increases the secretion of the nonamyloidogenic APP fragment, sbetaAPPalpha, and decreases the secretion of Abeta peptides from N2a cells and rat primary cerebrocortical neurons. These results raise the possibility that testosterone supplementation in elderly men may be protective in the treatment of AD.

Research paper thumbnail of Live discussion. From here to there: AbetaPP as an axonal transport receptor--how could this explain neurodegeneration in AD. 15 July 2002

Journal of Alzheimer's disease: JAD

Research paper thumbnail of Synapses, synaptic activity and intraneuronal abeta in Alzheimer's disease

Frontiers in aging neuroscience, 2010

beta-Amyloid peptide accumulation plays a central role in the pathogenesis of Alzheimer's dis... more beta-Amyloid peptide accumulation plays a central role in the pathogenesis of Alzheimer's disease. Aberrant beta-amyloid buildup in the brain has been shown to be present both in the extracellular space and within neurons. Synapses are important targets of beta-amyloid, and alterations in synapses better correlate with cognitive impairment than amyloid plaques or neurofibrillary tangles. The link between beta-amyloid and synapses became even tighter when it was discovered that beta-amyloid accumulates within synapses and that synaptic activity modulates beta-amyloid secretion. Currently, a central question in Alzheimer's disease research is what role synaptic activity plays in the disease process, and how specifically beta-amyloid is involved in the synaptic dysfunction that characterizes the disease.

Research paper thumbnail of Generation and regulation of beta-amyloid peptide variants by neurons

Journal of neurochemistry, 1998

Studies of processing of the Alzheimer beta-amyloid precursor protein (betaAPP) have been perform... more Studies of processing of the Alzheimer beta-amyloid precursor protein (betaAPP) have been performed to date mostly in continuous cell lines and indicate the existence of two principal metabolic pathways: the "beta-secretase" pathway, which generates beta-amyloid (A beta(1-40/42); approximately 4 kDa), and the "alpha-secretase" pathway, which generates a smaller fragment, the "p3" peptide (A beta(17-40/42); approximately 3 kDa). To determine whether similar processing events underlie betaAPP metabolism in neurons, media were examined following conditioning by primary neuronal cultures derived from embryonic day 17 rats. Immunoprecipitates of conditioned media derived from [35S]methionine pulse-labeled primary neuronal cultures contained 4- and 3-kDa A beta-related species. Radiosequencing analysis revealed that the 4-kDa band corresponded to conventional A beta beginning at position A beta(Asp1), whereas both radiosequencing and immunoprecipitation-mass ...

Research paper thumbnail of Apolipoprotein E, A beta-amyloid, and the molecular pathology of Alzheimer's disease. Therapeutic implications

Annals of the New York Academy of Sciences, Jan 16, 1996

Research paper thumbnail of Decreased senile plaque density in Alzheimer neocortex adjacent to an omental transposition

Neurological research, 1996

Post-mortem studies of the brain of an Alzheimer patient indicate fewer senile plaques in the cre... more Post-mortem studies of the brain of an Alzheimer patient indicate fewer senile plaques in the crests of cortical gyri underneath an omental transposition than in neighboring cortical areas.

Research paper thumbnail of Nonsteroidal selective androgen receptor modulators and selective estrogen receptor β agonists moderate cognitive deficits and amyloid-β levels in a mouse model of Alzheimer's disease

ACS chemical neuroscience, Jan 18, 2013

Decreases of the sex steroids, testosterone and estrogen, are associated with increased risk of A... more Decreases of the sex steroids, testosterone and estrogen, are associated with increased risk of Alzheimer's disease. Testosterone and estrogen supplementation improves cognitive deficits in animal models of Alzheimer's disease. Sex hormones play a role in the regulation of amyloid-β via induction of the amyloid-β degrading enzymes neprilysin and insulin-degrading enzyme. To mimic the effect of dihydrotestosterone (DHT), we administered a selective androgen receptor agonist, ACP-105, alone and in combination with the selective estrogen receptor β (ERβ) agonist AC-186 to male gonadectomized triple transgenic mice. We assessed long-term spatial memory in the Morris water maze, spontaneous locomotion, and anxiety-like behavior in the open field and in the elevated plus maze. We found that ACP-105 given alone decreases anxiety-like behavior. Furthermore, when ACP-105 is administered in combination with AC-186, they increase the amyloid-β degrading enzymes neprilysin and insulin-d...

Research paper thumbnail of DISTINCT LOCALIZATION OF BETA- AND GAMMA-SECRETASE IN RAT BRAIN SYNAPSES

Alzheimer's & Dementia, 2014

LRP1 as described for Fe65. Methods: Interaction between GULP1 molecules was analysed usingGULP1 ... more LRP1 as described for Fe65. Methods: Interaction between GULP1 molecules was analysed usingGULP1 constructs carrying two different epitope tags (HA-tagged or GFP-tagged). To confirm GULP1-dimerization we employed a protein fragment complementation assay (PCA) where GULP1 was fused to non-bioluminescent amino-or carboxy-terminal fragments of humanized Gaussia Luciferase (hGLuc) or non-fluorescence amino-or caboxy-terminal fragments of Venus-YFP. Specific GULP1-dimerization reconstitutes luciferase/venus and provides a measurable bioluminescent/ fluorescence signal. Results: Upon co-immunoprecipitation, we observed that the GFP-tagged GULP1 was precipitated with HA-tagged GULP1. To confirm our results we did a protein complementation assay. We observed GULP1 dimerization in living cells and found that co-expression of APP enhances dimerization of GULP1. Furthermore, we analysed localization of GULP1 dimers by confocal microscopy as well as nuclear extraction assays showing that GULP1 dimers can be found both in the cytosol and the nucleus. Complex formation of APP, GULP1 and LRP1 was analysed by triple-immunoprecipitation. We could show that GULP1 functions as a molecular bridge between APP and LRP1. Conclusions: Taken together, these data identify the dimerization properties of GULP1 in vivo. GULP1 forms dimers/oligomers both in the cytosol and the nucleus and the dimerization is further promoted by co-expression of APP. Additionally, GULP1 dimerization enables simultaneous binding of both APP and LRP1.

Research paper thumbnail of Lesion of the subiculum reduces the spread of amyloid beta pathology to interconnected brain regions in a mouse model of Alzheimer's disease

Acta neuropathologica communications, 2014

The progressive development of Alzheimer's disease (AD) pathology follows a spatiotemporal pa... more The progressive development of Alzheimer's disease (AD) pathology follows a spatiotemporal pattern in the human brain. In a transgenic (Tg) mouse model of AD expressing amyloid precursor protein (APP) with the arctic (E693G) mutation, pathology spreads along anatomically connected structures. Amyloid-β (Aβ) pathology first appears in the subiculum and is later detected in interconnected brain regions, including the retrosplenial cortex. We investigated whether the spatiotemporal pattern of Aβ pathology in the Tg APP arctic mice to interconnected brain structures can be interrupted by destroying neurons using a neurotoxin and thereby disconnecting the neural circuitry. We performed partial unilateral ibotenic acid lesions of the subiculum (first structure affected by Aβ pathology) in young Tg APParc mice, prior to the onset of pathology. We assessed Aβ/C99 pathology in mice aged up to 6 months after injecting ibotenate into the subiculum. Compared to the brains of intact Tg APP a...

Research paper thumbnail of Molecular Pathology of Dementia

Research paper thumbnail of Critical role of intraneuronal Aβ in Alzheimer's disease: Technical challenges in studying intracellular Aβ

Aims: Multiple lines of evidence have implicated β-amyloid (Aβ) in the pathogenesis of Alzheimer'... more Aims: Multiple lines of evidence have implicated β-amyloid (Aβ) in the pathogenesis of Alzheimer's disease (AD). However, the mechanism(s) whereby Aβ is involved in the disease process remains unclear. The dominant hypothesis in AD has been that Aβ initiates the disease via toxicity from secreted, extracellular Aβ aggregates. More recently, an alternative hypothesis has emerged focusing on a pool of Aβ that accumulates early on within AD vulnerable neurons of the brain. Although the topic of intraneuronal Aβ has been of major interest in the field, technical difficulties in detecting intraneuronal Aβ have also made this topic remarkably controversial. Here we review evidence pointing to the critical role of intraneuronal Aβ in AD and provide insights both into challenges faced in detecting intracellular Aβ and the prion-like properties of Aβ. Main methods: Immunoprecipitation and Western blot are used for Aβ detection. Key findings: We highlight that a standard biochemical method can underestimate intraneuronal Aβ and that extracellular Aβ can up-regulate intracellular Aβ. We also show that detergent can remove intraneuronal Aβ. Significance: There is a growing awareness that intraneuronal Aβ is a key pathogenic pool of Aβ involved in causing synapse dysfunction. Difficulties in detecting intraneuronal Aβ are an insufficient reason for ignoring this critical pool of Aβ.

Research paper thumbnail of Myotonia in colchicine myoneuropathy

Muscle and Nerve, 1996

Colchicine may induce a myoneuropathy in patients with renal insufficiency. To date, myotonia has... more Colchicine may induce a myoneuropathy in patients with renal insufficiency. To date, myotonia has not been described in this disorder. We recently studied 4 patients treated with routine doses of colchicine who, in the setting of renal insufficiency, developed a severe myoneuropathy characterized by prominent myotonic discharges on electromyography. In addition, 1 of the 4 patients had profound clinical myotonia. In the 3 patients in whom biopsies were performed, marked myopathic change with intracytoplasmic vacuolization was identified. All 4 patients improved rapidly with discontinuation of the medication. The patient in whom electrophysiologic studies were repeated had a complete resolution of the myotonic discharges. Colchicine myoneuropathy can present with prominent clinical and electrophysiologic myotonia that resolves completely with discontinuation of the medication.

Research paper thumbnail of Immunotherapy for Alzheimer disease

mAbs, 2009

Immunotherapy approaches for Alzheimer disease currently are among the leading therapeutic direct... more Immunotherapy approaches for Alzheimer disease currently are among the leading therapeutic directions for the disease. Active and passive immunotherapy against the beta-amyloid peptides that aggregate and accumulate in the brain of those afflicted by the disease have been shown by numerous groups to reduce plaque pathology and improve behavior in transgenic mouse models of the disease. Several ongoing immunotherapy clinical trials for Alzheimer disease are in progress. The background and ongoing challenges for these immunological approaches for the treatment of Alzheimer disease are discussed.

Research paper thumbnail of Accumulation of cellular prion protein within dystrophic neurites of amyloid plaques in the Alzheimer's disease brain

Neuropathology, 2011

Amyloid plaques, a well-known hallmark of Alzheimer&#... more Amyloid plaques, a well-known hallmark of Alzheimer's disease (AD), are formed by aggregated β-amyloid (Aβ). The cellular prion protein (PrPc) accumulates concomitantly with Aβ in amyloid plaques. One type of amyloid plaque, classified as a neuritic plaque, is composed of an amyloid core and surrounding dystrophic neurites. PrPc immunoreactivity reminiscent of dystrophic neurites is observed in neuritic plaques. Proteinase K treatment prior to immunohistochemistry removes PrPc immunoreactivity from amyloid plaques, whereas Aβ immunoreactivity is enhanced by this treatment. In the present study, we used a chemical pretreatment by a sarkosyl solution (0.1% sarkosyl, 75 mM NaOH, 2% NaCl), instead of proteinase K treatment, to evaluate PrPc accumulation within amyloid plaques. Since PrPc within amyloid plaques is removed by this chemical pretreatment, we can recognize that the PrP species deposits within amyloid plaques were PrPc. We could observe that PrPc accumulation in dystrophic neurites occurred differently compared with Aβ or hyperphosphorylated tau aggregation in the AD brain. These results could support the hypothesis that PrPc accumulation in dystrophic neurites reflects a response to impairments in cellular degradation, endocytosis, or transport mechanisms associated with AD rather than a non-specific cross-reactivity between PrPc and aggregated Aβ or tau.

Research paper thumbnail of mTOR: At the crossroads of aging, chaperones, and Alzheimer's disease

Journal of Neurochemistry, 2012

Research paper thumbnail of Pathology of Synapses and Dendritic Spines

Research paper thumbnail of SYNAPTIC ALTERATIONS IN APP KNOCKOUT NEURONS

Alzheimer's & Dementia, 2014

Background: Alzheimer's disease (AD) and diabetes are thought to share similar pathological mecha... more Background: Alzheimer's disease (AD) and diabetes are thought to share similar pathological mechanisms. For instance, brain insulin signaling is disrupted in AD patients and anti-diabetic strategies appear to rescue ADlike pathology in animal models. Double-stranded RNA-dependent protein kinase (PKR) underlies peripheral insulin resistance in a mechanism driven by pro-inflammatory cytokines, such as tumor necrosis factor a (TNFa). PKR phosphorylates eukaryotic translation initiation factor 2 a (eIF2 a -P) in response to cellular stress, and AD brains exhibit elevated phospho-PKR and eIF2 a -P levels. This mechanism attenuates global protein synthesis in neurons and might impact normal synapse function in Alzheimer's disease. Methods: Our in vitro model consisted of cultured hippocampal neurons exposed to amyloid-b (A b) oligomers, recognized as central AD toxins, and signaling pathways were manipulated by pharmacological treatments. Morphological and biochemical analyses were then performed. For in vivo studies, adult mice intracerebroventricularly (i.c.v.) injected with A b oligomer preparations and APPSwe/PS1 D E9 transgenic mice were subjected to behavioral assays and their hippocampi were analyzed by immunoblotting. Knockout mice for TNFa receptor 1 (TNFR1) and PKR were also employed. Finally, we established a non-human primate AD model by i.c.v. injecting cynomolgus monkeys with A b oligomers. Primate hippocampi were assessed for PKR and eIF2 a phosphorylation through immunostaining techniques. Results: We found that PKR responds to A b oligomers and causes eIF2 a -P in the hippocampus in a TNFa -dependent process. Brain PKR and eIF2 a phosphorylation are elevated in AD animal models, including APPSwe/PS1 D E9 transgenic mice and oligomer-injected cynomolgus monkeys. Further, genetic suppression of either TNFR1 or PKR abrogated A b oligomer-dependent brain eIF2a-P and cognitive impairment in mice. Importantly, we found that TNFa/PKR signaling inhibition prevented synapse loss caused by A b oligomers. Conclusions: Our results demonstrate that A b oligomers trigger a pro-inflammatory signaling orchestrated by TNFa, PKR and eIF2 a -P, ultimately leading to synapse loss and cognitive impairment. These observations reveal a critical pathogenic mechanism connecting Alzheimer's disease to diabetes, and, in harmony with other recent reports, our findings provide exciting grounds for novel drug targets in AD.

Research paper thumbnail of Alzheimer β-amyloid peptides: Normal and abnormal localization

Histology and histopathology

Alzheimer's disease (AD) neuropathology is characterized by accumulation of "senile" plaques (SPs... more Alzheimer's disease (AD) neuropathology is characterized by accumulation of "senile" plaques (SPs) and neurofibrillary tangles (NFTs) in vulnerable brain regions. SPs are principally composed of aggregates of up to 42/43 amino acid ß-amyloid (Aß) peptides. The discovery of familial AD (FAD) mutations in the genes for the amyloid precursor protein (APP) and presenilins (PSs), all of which increase Aß42 production, support the view that Aß is centrally involved in the pathogenesis of AD. Aß42 aggregates readily, and is thought to seed the formation of fibrils, which then act as templates for plaque formation. Aß is generated by the sequential intracellular cleavage of APP by ßsecretase to generate the N-terminal end of Aß, and intramembranous cleavage by γ-secretase to generate the C-terminal end. Cell biological studies have demonstrated that Aß is generated in the ER, Golgi, and endosomal/lysosomal system. A central question involving the role of Aß in AD concerns how Aß causes disease and whether it is extracellular Aß deposition and/or intracellular Aß accumulation that initiates the disease process. The most prevalent view is that SPs are composed of extracellular deposits of secreted Aß and that Aß causes toxicity to surrounding neurons as extracellular SP. The recent emphasis on the intracellular biology of APP and Aß has led some investigators to consider the possibility that intraneuronal Aß may directly cause toxicity. In this review we will outline current knowledge of the localization of both intracellular and extracellular Aß.

Research paper thumbnail of Cellular and molecular basis of beta-amyloid precursor protein metabolism

Research paper thumbnail of ADAM10 and BACE1 are localized to synaptic vesicles

Journal of neurochemistry, Jan 22, 2015

Synaptic degeneration and accumulation of the neurotoxic amyloid β-peptide (Aβ) in the brain are ... more Synaptic degeneration and accumulation of the neurotoxic amyloid β-peptide (Aβ) in the brain are hallmarks of Alzheimer disease. Aβ is produced by sequential cleavage of its precursor protein, APP, by the β-secretase BACE1 and γ-secretase. However, Aβ generation is precluded if APP is cleaved by the α-secretase ADAM10 instead of BACE1. We have previously shown that Aβ can be produced locally at the synapse. To study the synaptic localization of the APP processing enzymes we used western blotting to demonstrate that, compared to total brain homogenate, ADAM10 and BACE1 were greatly enriched in synaptic vesicles isolated from rat brain using controlled-pore glass chromatography, whereas Presenilin1 was the only enriched component of the γ-secretase complex. Moreover, we detected ADAM10 activity in synaptic vesicles and enrichment of the intermediate APP-C-terminal fractions (APP-CTFs). We confirmed the western blotting findings using in situ proximity ligation assay to demonstrate clo...

Research paper thumbnail of Testosterone reduces neuronal secretion of Alzheimer's -amyloid peptides

Proceedings of the National Academy of Sciences

Alzheimer's disease (AD) is characterized by the age-related deposition of beta-amyloid (... more Alzheimer's disease (AD) is characterized by the age-related deposition of beta-amyloid (Abeta) 40/42 peptide aggregates in vulnerable brain regions. Multiple levels of evidence implicate a central role for Abeta in the pathophysiology of AD. Abeta peptides are generated by the regulated cleavage of an approximately 700-aa Abeta precursor protein (betaAPP). Full-length betaAPP can undergo proteolytic cleavage either within the Abeta domain to generate secreted sbetaAPPalpha or at the N- and C-terminal domain(s) of Abeta to generate amyloidogenic Abeta peptides. Several epidemiological studies have reported that estrogen replacement therapy protects against the development of AD in postmenopausal women. We previously reported that treating cultured neurons with 17beta-estradiol reduced the secretion of Abeta40/42 peptides, suggesting that estrogen replacement therapy may protect women against the development of AD by regulating betaAPP metabolism. Increasing evidence indicates that testosterone, especially bioavailable testosterone, decreases with age in older men and in postmenopausal women. We report here that treatment with testosterone increases the secretion of the nonamyloidogenic APP fragment, sbetaAPPalpha, and decreases the secretion of Abeta peptides from N2a cells and rat primary cerebrocortical neurons. These results raise the possibility that testosterone supplementation in elderly men may be protective in the treatment of AD.

Research paper thumbnail of Live discussion. From here to there: AbetaPP as an axonal transport receptor--how could this explain neurodegeneration in AD. 15 July 2002

Journal of Alzheimer's disease: JAD

Research paper thumbnail of Synapses, synaptic activity and intraneuronal abeta in Alzheimer's disease

Frontiers in aging neuroscience, 2010

beta-Amyloid peptide accumulation plays a central role in the pathogenesis of Alzheimer's dis... more beta-Amyloid peptide accumulation plays a central role in the pathogenesis of Alzheimer's disease. Aberrant beta-amyloid buildup in the brain has been shown to be present both in the extracellular space and within neurons. Synapses are important targets of beta-amyloid, and alterations in synapses better correlate with cognitive impairment than amyloid plaques or neurofibrillary tangles. The link between beta-amyloid and synapses became even tighter when it was discovered that beta-amyloid accumulates within synapses and that synaptic activity modulates beta-amyloid secretion. Currently, a central question in Alzheimer's disease research is what role synaptic activity plays in the disease process, and how specifically beta-amyloid is involved in the synaptic dysfunction that characterizes the disease.

Research paper thumbnail of Generation and regulation of beta-amyloid peptide variants by neurons

Journal of neurochemistry, 1998

Studies of processing of the Alzheimer beta-amyloid precursor protein (betaAPP) have been perform... more Studies of processing of the Alzheimer beta-amyloid precursor protein (betaAPP) have been performed to date mostly in continuous cell lines and indicate the existence of two principal metabolic pathways: the "beta-secretase" pathway, which generates beta-amyloid (A beta(1-40/42); approximately 4 kDa), and the "alpha-secretase" pathway, which generates a smaller fragment, the "p3" peptide (A beta(17-40/42); approximately 3 kDa). To determine whether similar processing events underlie betaAPP metabolism in neurons, media were examined following conditioning by primary neuronal cultures derived from embryonic day 17 rats. Immunoprecipitates of conditioned media derived from [35S]methionine pulse-labeled primary neuronal cultures contained 4- and 3-kDa A beta-related species. Radiosequencing analysis revealed that the 4-kDa band corresponded to conventional A beta beginning at position A beta(Asp1), whereas both radiosequencing and immunoprecipitation-mass ...

Research paper thumbnail of Apolipoprotein E, A beta-amyloid, and the molecular pathology of Alzheimer's disease. Therapeutic implications

Annals of the New York Academy of Sciences, Jan 16, 1996

Research paper thumbnail of Decreased senile plaque density in Alzheimer neocortex adjacent to an omental transposition

Neurological research, 1996

Post-mortem studies of the brain of an Alzheimer patient indicate fewer senile plaques in the cre... more Post-mortem studies of the brain of an Alzheimer patient indicate fewer senile plaques in the crests of cortical gyri underneath an omental transposition than in neighboring cortical areas.

Research paper thumbnail of Nonsteroidal selective androgen receptor modulators and selective estrogen receptor β agonists moderate cognitive deficits and amyloid-β levels in a mouse model of Alzheimer's disease

ACS chemical neuroscience, Jan 18, 2013

Decreases of the sex steroids, testosterone and estrogen, are associated with increased risk of A... more Decreases of the sex steroids, testosterone and estrogen, are associated with increased risk of Alzheimer's disease. Testosterone and estrogen supplementation improves cognitive deficits in animal models of Alzheimer's disease. Sex hormones play a role in the regulation of amyloid-β via induction of the amyloid-β degrading enzymes neprilysin and insulin-degrading enzyme. To mimic the effect of dihydrotestosterone (DHT), we administered a selective androgen receptor agonist, ACP-105, alone and in combination with the selective estrogen receptor β (ERβ) agonist AC-186 to male gonadectomized triple transgenic mice. We assessed long-term spatial memory in the Morris water maze, spontaneous locomotion, and anxiety-like behavior in the open field and in the elevated plus maze. We found that ACP-105 given alone decreases anxiety-like behavior. Furthermore, when ACP-105 is administered in combination with AC-186, they increase the amyloid-β degrading enzymes neprilysin and insulin-d...

Research paper thumbnail of DISTINCT LOCALIZATION OF BETA- AND GAMMA-SECRETASE IN RAT BRAIN SYNAPSES

Alzheimer's & Dementia, 2014

LRP1 as described for Fe65. Methods: Interaction between GULP1 molecules was analysed usingGULP1 ... more LRP1 as described for Fe65. Methods: Interaction between GULP1 molecules was analysed usingGULP1 constructs carrying two different epitope tags (HA-tagged or GFP-tagged). To confirm GULP1-dimerization we employed a protein fragment complementation assay (PCA) where GULP1 was fused to non-bioluminescent amino-or carboxy-terminal fragments of humanized Gaussia Luciferase (hGLuc) or non-fluorescence amino-or caboxy-terminal fragments of Venus-YFP. Specific GULP1-dimerization reconstitutes luciferase/venus and provides a measurable bioluminescent/ fluorescence signal. Results: Upon co-immunoprecipitation, we observed that the GFP-tagged GULP1 was precipitated with HA-tagged GULP1. To confirm our results we did a protein complementation assay. We observed GULP1 dimerization in living cells and found that co-expression of APP enhances dimerization of GULP1. Furthermore, we analysed localization of GULP1 dimers by confocal microscopy as well as nuclear extraction assays showing that GULP1 dimers can be found both in the cytosol and the nucleus. Complex formation of APP, GULP1 and LRP1 was analysed by triple-immunoprecipitation. We could show that GULP1 functions as a molecular bridge between APP and LRP1. Conclusions: Taken together, these data identify the dimerization properties of GULP1 in vivo. GULP1 forms dimers/oligomers both in the cytosol and the nucleus and the dimerization is further promoted by co-expression of APP. Additionally, GULP1 dimerization enables simultaneous binding of both APP and LRP1.

Research paper thumbnail of Lesion of the subiculum reduces the spread of amyloid beta pathology to interconnected brain regions in a mouse model of Alzheimer's disease

Acta neuropathologica communications, 2014

The progressive development of Alzheimer's disease (AD) pathology follows a spatiotemporal pa... more The progressive development of Alzheimer's disease (AD) pathology follows a spatiotemporal pattern in the human brain. In a transgenic (Tg) mouse model of AD expressing amyloid precursor protein (APP) with the arctic (E693G) mutation, pathology spreads along anatomically connected structures. Amyloid-β (Aβ) pathology first appears in the subiculum and is later detected in interconnected brain regions, including the retrosplenial cortex. We investigated whether the spatiotemporal pattern of Aβ pathology in the Tg APP arctic mice to interconnected brain structures can be interrupted by destroying neurons using a neurotoxin and thereby disconnecting the neural circuitry. We performed partial unilateral ibotenic acid lesions of the subiculum (first structure affected by Aβ pathology) in young Tg APParc mice, prior to the onset of pathology. We assessed Aβ/C99 pathology in mice aged up to 6 months after injecting ibotenate into the subiculum. Compared to the brains of intact Tg APP a...

Research paper thumbnail of Molecular Pathology of Dementia

Research paper thumbnail of Critical role of intraneuronal Aβ in Alzheimer's disease: Technical challenges in studying intracellular Aβ

Aims: Multiple lines of evidence have implicated β-amyloid (Aβ) in the pathogenesis of Alzheimer'... more Aims: Multiple lines of evidence have implicated β-amyloid (Aβ) in the pathogenesis of Alzheimer's disease (AD). However, the mechanism(s) whereby Aβ is involved in the disease process remains unclear. The dominant hypothesis in AD has been that Aβ initiates the disease via toxicity from secreted, extracellular Aβ aggregates. More recently, an alternative hypothesis has emerged focusing on a pool of Aβ that accumulates early on within AD vulnerable neurons of the brain. Although the topic of intraneuronal Aβ has been of major interest in the field, technical difficulties in detecting intraneuronal Aβ have also made this topic remarkably controversial. Here we review evidence pointing to the critical role of intraneuronal Aβ in AD and provide insights both into challenges faced in detecting intracellular Aβ and the prion-like properties of Aβ. Main methods: Immunoprecipitation and Western blot are used for Aβ detection. Key findings: We highlight that a standard biochemical method can underestimate intraneuronal Aβ and that extracellular Aβ can up-regulate intracellular Aβ. We also show that detergent can remove intraneuronal Aβ. Significance: There is a growing awareness that intraneuronal Aβ is a key pathogenic pool of Aβ involved in causing synapse dysfunction. Difficulties in detecting intraneuronal Aβ are an insufficient reason for ignoring this critical pool of Aβ.

Research paper thumbnail of Myotonia in colchicine myoneuropathy

Muscle and Nerve, 1996

Colchicine may induce a myoneuropathy in patients with renal insufficiency. To date, myotonia has... more Colchicine may induce a myoneuropathy in patients with renal insufficiency. To date, myotonia has not been described in this disorder. We recently studied 4 patients treated with routine doses of colchicine who, in the setting of renal insufficiency, developed a severe myoneuropathy characterized by prominent myotonic discharges on electromyography. In addition, 1 of the 4 patients had profound clinical myotonia. In the 3 patients in whom biopsies were performed, marked myopathic change with intracytoplasmic vacuolization was identified. All 4 patients improved rapidly with discontinuation of the medication. The patient in whom electrophysiologic studies were repeated had a complete resolution of the myotonic discharges. Colchicine myoneuropathy can present with prominent clinical and electrophysiologic myotonia that resolves completely with discontinuation of the medication.

Research paper thumbnail of Immunotherapy for Alzheimer disease

mAbs, 2009

Immunotherapy approaches for Alzheimer disease currently are among the leading therapeutic direct... more Immunotherapy approaches for Alzheimer disease currently are among the leading therapeutic directions for the disease. Active and passive immunotherapy against the beta-amyloid peptides that aggregate and accumulate in the brain of those afflicted by the disease have been shown by numerous groups to reduce plaque pathology and improve behavior in transgenic mouse models of the disease. Several ongoing immunotherapy clinical trials for Alzheimer disease are in progress. The background and ongoing challenges for these immunological approaches for the treatment of Alzheimer disease are discussed.

Research paper thumbnail of Accumulation of cellular prion protein within dystrophic neurites of amyloid plaques in the Alzheimer's disease brain

Neuropathology, 2011

Amyloid plaques, a well-known hallmark of Alzheimer&#... more Amyloid plaques, a well-known hallmark of Alzheimer's disease (AD), are formed by aggregated β-amyloid (Aβ). The cellular prion protein (PrPc) accumulates concomitantly with Aβ in amyloid plaques. One type of amyloid plaque, classified as a neuritic plaque, is composed of an amyloid core and surrounding dystrophic neurites. PrPc immunoreactivity reminiscent of dystrophic neurites is observed in neuritic plaques. Proteinase K treatment prior to immunohistochemistry removes PrPc immunoreactivity from amyloid plaques, whereas Aβ immunoreactivity is enhanced by this treatment. In the present study, we used a chemical pretreatment by a sarkosyl solution (0.1% sarkosyl, 75 mM NaOH, 2% NaCl), instead of proteinase K treatment, to evaluate PrPc accumulation within amyloid plaques. Since PrPc within amyloid plaques is removed by this chemical pretreatment, we can recognize that the PrP species deposits within amyloid plaques were PrPc. We could observe that PrPc accumulation in dystrophic neurites occurred differently compared with Aβ or hyperphosphorylated tau aggregation in the AD brain. These results could support the hypothesis that PrPc accumulation in dystrophic neurites reflects a response to impairments in cellular degradation, endocytosis, or transport mechanisms associated with AD rather than a non-specific cross-reactivity between PrPc and aggregated Aβ or tau.

Research paper thumbnail of mTOR: At the crossroads of aging, chaperones, and Alzheimer's disease

Journal of Neurochemistry, 2012

Research paper thumbnail of Pathology of Synapses and Dendritic Spines

Research paper thumbnail of SYNAPTIC ALTERATIONS IN APP KNOCKOUT NEURONS

Alzheimer's & Dementia, 2014

Background: Alzheimer's disease (AD) and diabetes are thought to share similar pathological mecha... more Background: Alzheimer's disease (AD) and diabetes are thought to share similar pathological mechanisms. For instance, brain insulin signaling is disrupted in AD patients and anti-diabetic strategies appear to rescue ADlike pathology in animal models. Double-stranded RNA-dependent protein kinase (PKR) underlies peripheral insulin resistance in a mechanism driven by pro-inflammatory cytokines, such as tumor necrosis factor a (TNFa). PKR phosphorylates eukaryotic translation initiation factor 2 a (eIF2 a -P) in response to cellular stress, and AD brains exhibit elevated phospho-PKR and eIF2 a -P levels. This mechanism attenuates global protein synthesis in neurons and might impact normal synapse function in Alzheimer's disease. Methods: Our in vitro model consisted of cultured hippocampal neurons exposed to amyloid-b (A b) oligomers, recognized as central AD toxins, and signaling pathways were manipulated by pharmacological treatments. Morphological and biochemical analyses were then performed. For in vivo studies, adult mice intracerebroventricularly (i.c.v.) injected with A b oligomer preparations and APPSwe/PS1 D E9 transgenic mice were subjected to behavioral assays and their hippocampi were analyzed by immunoblotting. Knockout mice for TNFa receptor 1 (TNFR1) and PKR were also employed. Finally, we established a non-human primate AD model by i.c.v. injecting cynomolgus monkeys with A b oligomers. Primate hippocampi were assessed for PKR and eIF2 a phosphorylation through immunostaining techniques. Results: We found that PKR responds to A b oligomers and causes eIF2 a -P in the hippocampus in a TNFa -dependent process. Brain PKR and eIF2 a phosphorylation are elevated in AD animal models, including APPSwe/PS1 D E9 transgenic mice and oligomer-injected cynomolgus monkeys. Further, genetic suppression of either TNFR1 or PKR abrogated A b oligomer-dependent brain eIF2a-P and cognitive impairment in mice. Importantly, we found that TNFa/PKR signaling inhibition prevented synapse loss caused by A b oligomers. Conclusions: Our results demonstrate that A b oligomers trigger a pro-inflammatory signaling orchestrated by TNFa, PKR and eIF2 a -P, ultimately leading to synapse loss and cognitive impairment. These observations reveal a critical pathogenic mechanism connecting Alzheimer's disease to diabetes, and, in harmony with other recent reports, our findings provide exciting grounds for novel drug targets in AD.