Jens Brodbeck | Genentech - Academia.edu (original) (raw)

Papers by Jens Brodbeck

Research paper thumbnail of Rosiglitazone increases dendritic spine density and rescues spine loss caused by apolipoprotein E4 in primary cortical neurons

Proceedings of the National Academy of Sciences, 2008

Convergent evidence has revealed an association between insulin resistance and Alzheimer's diseas... more Convergent evidence has revealed an association between insulin resistance and Alzheimer's disease (AD), and the peroxisome proliferator-activated receptor-␥ (PPAR-␥) agonist, rosiglitazone, an insulin sensitizer and mitochondrial activator, improves cognition in patients with early or mild-to-moderate AD. Apolipoprotein (apo) E4, a major genetic risk factor for AD, exerts neuropathological effects through multiple pathways, including impairment of dendritic spine structure and mitochondrial function. Here we show that rosiglitazone significantly increased dendritic spine density in a dose-dependent manner in cultured primary cortical rat neurons. This effect was abolished by the PPAR-␥-specific antagonist, GW9662, suggesting that rosiglitazone exerts this effect by activating the PPAR-␥ pathway. Furthermore, the Cterminal-truncated fragment of apoE4 significantly decreased dendritic spine density. Rosiglitazone rescued this detrimental effect. Thus, rosiglitazone might improve cognition in AD patients by increasing dendritic spine density.

Research paper thumbnail of Ducky mouse phenotype of epilepsy and ataxia is associated with mutations in the Cacna2d2 gene and decreased calcium channel current in cerebellar Purkinje cells

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 2001

The mouse mutant ducky, a model for absence epilepsy, is characterized by spike-wave seizures and... more The mouse mutant ducky, a model for absence epilepsy, is characterized by spike-wave seizures and ataxia. The ducky gene was mapped previously to distal mouse chromosome 9. High-resolution genetic and physical mapping has resulted in the identification of the Cacna2d2 gene encoding the alpha2delta2 voltage-dependent calcium channel subunit. Mutations in Cacna2d2 were found to underlie the ducky phenotype in the original ducky (du) strain and in a newly identified strain (du(2J)). Both mutations are predicted to result in loss of the full-length alpha2delta2 protein. Functional analysis shows that the alpha2delta2 subunit increases the maximum conductance of the alpha1A/beta4 channel combination when coexpressed in vitro in Xenopus oocytes. The Ca(2+) channel current in acutely dissociated du/du cerebellar Purkinje cells was reduced, with no change in single-channel conductance. In contrast, no effect on Ca(2+) channel current was seen in cerebellar granule cells, results consistent ...

Research paper thumbnail of Arf4 Determines Dentate Gyrus-Mediated Pattern Separation by Regulating Dendritic Spine Development

PLoS ONE, 2012

The ability to distinguish between similar experiences is a critical feature of episodic memory a... more The ability to distinguish between similar experiences is a critical feature of episodic memory and is primarily regulated by the dentate gyrus (DG) region of the hippocampus. However, the molecular mechanisms underlying such pattern separation tasks are poorly understood. We report a novel role for the small GTPase ADP ribosylation factor 4 (Arf4) in controlling pattern separation by regulating dendritic spine development. Arf4 +/2 mice at 4-5 months of age display severe impairments in a pattern separation task, as well as significant dendritic spine loss and smaller miniature excitatory postsynaptic currents (mEPSCs) in granule cells of the DG. Arf4 knockdown also decreases spine density in primary neurons, whereas Arf4 overexpression promotes spine development. A constitutively active form of Arf4, Arf4-Q71L, promotes spine density to an even greater extent than wildtype Arf4, whereas the inactive Arf4-T31N mutant does not increase spine density relative to controls. Arf49s effects on spine development are regulated by ASAP1, a GTPase-activating protein that modulates Arf4 GTPase activity. ASAP1 overexpression decreases spine density, and this effect is partially rescued by concomitant overexpression of wildtype Arf4 or Arf4-Q71L. In addition, Arf4 overexpression rescues spine loss in primary neurons from an Alzheimer's disease-related apolipoprotein (apo) E4 mouse model. Our findings suggest that Arf4 is a critical modulator of DG-mediated pattern separation by regulating dendritic spine development.

Research paper thumbnail of Intron-3 Retention/Splicing Controls Neuronal Expression of Apolipoprotein E in the CNS

Journal of Neuroscience, 2008

Neuronal expression of apolipoprotein (apo) E4 may contribute to the pathogenesis of Alzheimer&am... more Neuronal expression of apolipoprotein (apo) E4 may contribute to the pathogenesis of Alzheimer's disease (AD). In studying how apoE expression is regulated in neurons, we identified a splicing variant of apoE mRNA with intron-3 retention (apoE-I3). ApoE-I3 mRNA was detected in neuronal cell lines and primary neurons, but not in astrocytic cell lines or primary astrocytes, from humans and mice by reverse transcription (RT)-PCR. In both wild-type and human apoE knock-in mice, apoE-I3 was found predominantly in cortical and hippocampal neurons by in situ hybridization. Cell fractionation and quantitative RT-PCR revealed that over 98% of the apoE-I3 mRNA was retained in the nucleus without protein translation. In transfected primary neurons, apoE expression increased dramatically when intron-3 was deleted from a genomic DNA construct and decreased markedly when intron-3 was inserted into a cDNA construct, suggesting that intron-3 retention/splicing controls apoE expression in neurons. In response to excitotoxic challenge, the apoE-I3 mRNA was markedly increased in morphologically normal hippocampal neurons but reduced in degenerating hippocampal neurons in mice; apoE mRNA showed the opposite pattern. This apparent precursor-product relationship between apoE-I3 and apoE mRNA was supported by a transcriptional inhibition study. Thus, neuronal expression of apoE is controlled by transcription of apoE-I3 under normal conditions and by processing of apoE-I3 into mature apoE mRNA in response to injury.

Research paper thumbnail of Tau Reduction Prevents A -Induced Defects in Axonal Transport

Science, 2010

Amyloid-b (Ab) peptides, derived from the amyloid precursor protein, and the microtubule-associat... more Amyloid-b (Ab) peptides, derived from the amyloid precursor protein, and the microtubule-associated protein tau are key pathogenic factors in Alzheimer's disease (AD). How exactly they impair cognitive functions is unknown. We assessed the effects of Ab and tau on axonal transport of mitochondria and the neurotrophin receptor TrkA, cargoes that are critical for neuronal function and survival and whose distributions are altered in AD. Ab oligomers rapidly inhibited axonal transport of these cargoes in wild-type neurons. Lowering tau levels prevented these defects without affecting baseline axonal transport. Thus, Ab requires tau to impair axonal transport, and tau reduction protects against Ab-induced axonal transport defects.

Research paper thumbnail of Rosiglitazone increases dendritic spine density and rescues spine loss caused by apolipoprotein E4 in primary cortical neurons

Proceedings of the National Academy of Sciences, 2008

Convergent evidence has revealed an association between insulin resistance and Alzheimer's diseas... more Convergent evidence has revealed an association between insulin resistance and Alzheimer's disease (AD), and the peroxisome proliferator-activated receptor-␥ (PPAR-␥) agonist, rosiglitazone, an insulin sensitizer and mitochondrial activator, improves cognition in patients with early or mild-to-moderate AD. Apolipoprotein (apo) E4, a major genetic risk factor for AD, exerts neuropathological effects through multiple pathways, including impairment of dendritic spine structure and mitochondrial function. Here we show that rosiglitazone significantly increased dendritic spine density in a dose-dependent manner in cultured primary cortical rat neurons. This effect was abolished by the PPAR-␥-specific antagonist, GW9662, suggesting that rosiglitazone exerts this effect by activating the PPAR-␥ pathway. Furthermore, the Cterminal-truncated fragment of apoE4 significantly decreased dendritic spine density. Rosiglitazone rescued this detrimental effect. Thus, rosiglitazone might improve cognition in AD patients by increasing dendritic spine density.

Research paper thumbnail of Small Molecule Structure Correctors Abolish Detrimental Effects of Apolipoprotein E4 in Cultured Neurons

Journal of Biological Chemistry, 2012

Background: Apolipoprotein E4 (apoE4), the major gene involved in Alzheimer disease, has a unique... more Background: Apolipoprotein E4 (apoE4), the major gene involved in Alzheimer disease, has a unique structure, intramolecular domain interaction, that is associated with neuropathology. Results: Potent small molecule structure correctors block apoE4 domain interaction and reverse apoE4 detrimental effects in cultured neurons. Conclusion: Structure correctors negate the detrimental effects of apoE4 in neurons. Significance: ApoE4 structure correctors could represent a therapeutic approach for treating apoE4-associated neuropathology.

Research paper thumbnail of Structure-dependent Impairment of Intracellular Apolipoprotein E4 Trafficking and Its Detrimental Effects Are Rescued by Small-molecule Structure Correctors

Journal of Biological Chemistry, 2011

Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer disease (AD) and likely co... more Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer disease (AD) and likely contributes to neuropathology through various pathways. Here we report that the intracellular trafficking of apoE4 is impaired in Neuro-2a cells and primary neurons, as shown by measuring fluorescence recovery after photobleaching. In Neuro-2a cells, more apoE4 than apoE3 molecules remained immobilized in the endoplasmic reticulum (ER) and the Golgi apparatus, and the lateral motility of apoE4 was significantly lower in the Golgi apparatus (but not in the ER) than that of apoE3. Likewise, the immobile fraction was larger, and the lateral motility was lower for apoE4 than apoE3 in mouse primary hippocampal neurons. ApoE4 with the R61T mutation, which abolishes apoE4 domain interaction, was less immobilized, and its lateral motility was comparable with that of apoE3. The trafficking impairment of apoE4 was also rescued by disrupting domain interaction with the small-molecule structure correctors GIND25 and PH002. PH002 also rescued apoE4-induced impairments of neurite outgrowth in Neuro-2a cells and dendritic spine development in primary neurons. ApoE4 did not affect trafficking of amyloid precursor protein, another AD-related protein, through the secretory pathway. Thus, domain interaction renders more newly synthesized apoE4 molecules immobile and slows their trafficking along the secretory pathway. Correcting the pathological structure of apoE4 by disrupting domain interaction is a potential therapeutic approach to treat or prevent AD related to apoE4.

Research paper thumbnail of The Ducky Mutation in Cacna2d2 Results in Altered Purkinje Cell Morphology and Is Associated with the Expression of a Truncated alpha 2delta -2 Protein with Abnormal Function

Journal of Biological Chemistry, 2002

The mouse mutant ducky, a model for absence epilepsy, is characterized by spike-wave seizures and... more The mouse mutant ducky, a model for absence epilepsy, is characterized by spike-wave seizures and cerebellar ataxia. A mutation in Cacna2d2, the gene encoding the ␣2␦-2 voltage-dependent calcium channel accessory subunit, has been found to underlie the ducky phenotype. The ␣2␦-2 mRNA is strongly expressed in cerebellar Purkinje cells. We show that du/du mice have abnormalities in their Purkinje cell dendritic tree. The mutation in ␣2␦-2 results in the introduction of a premature stop codon and predicts the expression of a truncated protein encoded by the first three exons of Cacna2d2, followed by 8 novel amino acids. We show that both mRNA and protein corresponding to this predicted transcript are expressed in du/du cerebellum and present in Purkinje cells. Whereas the ␣2␦-2 subunit increased the peak current density of the Ca V 2.1/␤ 4 channel combination when co-expressed in vitro, co-expression with the truncated mutant ␣2␦-2 protein reduced current density, indicating that it may contribute to the du phenotype.

Research paper thumbnail of Apolipoprotein E4 impairs mitochondrial function and increases reactive oxygen species in neuronal cells

Alzheimer's & Dementia, 2009

Research paper thumbnail of Arf4 regulates dendritic spine development in mouse primary neurons

Alzheimer's & Dementia, 2010

co-immunoprecipitated with DISC1 at the endogenous protein level. Knockdown of DISC1 (lentivirus-... more co-immunoprecipitated with DISC1 at the endogenous protein level. Knockdown of DISC1 (lentivirus-mediated shRNA to DISC1) in mature primary cortical neurons, elicited no change in the levels of full-length APP (both mature and immature isoforms). In contrast, knockdown of DISC1 led to a significant increase in the levels of intracellular APP-C-terminal fragments C83 and C99. Knockdown of DISC1 also significantly enhanced sAPPa levels. Interestingly, we observed that DISC1 knockdown significantly decreased the levels of Ab42 and Ab40. The knockdown effects of DISC1 by RNAi on APP-CTFs, sAPPa and Ab 42/40 were successfully rescued by co-expression of wild-type DISC1. In the next step, we addressed whether DISC1 influences APP processing by using DISC1 knockout (KO) mice. We observed a significant increase in both C83 and C99 APP CTFs, with no change in the total APP levels in the DISC1 KO mice, as was the case in the primary neurons. Conclusions: DISC1 affects the processing of APP and generation of Ab in primary neuron cultures. Our goal is to characterize a novel mechanism of the regulation of APP processing/metabolism by DISC1.

Research paper thumbnail of O3-03-03: Apolipoprotein E4 and its fragment impair mitochondrial dynamics in neuronal cultures

Alzheimer's & Dementia, 2008

Research paper thumbnail of Effect of selective LRRK2 kinase inhibition on nonhuman primate lung

Science translational medicine, Jan 4, 2015

Inhibition of the kinase activity of leucine-rich repeat kinase 2 (LRRK2) is under investigation ... more Inhibition of the kinase activity of leucine-rich repeat kinase 2 (LRRK2) is under investigation as a possible treatment for Parkinson's disease. However, there is no clinical validation as yet, and the safety implications of targeting LRRK2 kinase activity are not well understood. We evaluated the potential safety risks by comparing human and mouse LRRK2 mRNA tissue expression, by analyzing a Lrrk2 knockout mouse model, and by testing selective brain-penetrating LRRK2 kinase inhibitors in multiple species. LRRK2 mRNA tissue expression was comparable between species. Phenotypic analysis of Lrrk2 knockout mice revealed morphologic changes in lungs and kidneys, similar to those reported previously. However, in preclinical toxicity assessments in rodents, no pulmonary or renal changes were induced by two distinct LRRK2 kinase inhibitors. Both of these kinase inhibitors induced abnormal cytoplasmic accumulation of secretory lysosome-related organelles known as lamellar bodies in typ...

Research paper thumbnail of Rosiglitazone increases dendritic spine density and rescues spine loss caused by apolipoprotein E4 in primary cortical neurons

Proceedings of the National Academy of Sciences, 2008

Convergent evidence has revealed an association between insulin resistance and Alzheimer's diseas... more Convergent evidence has revealed an association between insulin resistance and Alzheimer's disease (AD), and the peroxisome proliferator-activated receptor-␥ (PPAR-␥) agonist, rosiglitazone, an insulin sensitizer and mitochondrial activator, improves cognition in patients with early or mild-to-moderate AD. Apolipoprotein (apo) E4, a major genetic risk factor for AD, exerts neuropathological effects through multiple pathways, including impairment of dendritic spine structure and mitochondrial function. Here we show that rosiglitazone significantly increased dendritic spine density in a dose-dependent manner in cultured primary cortical rat neurons. This effect was abolished by the PPAR-␥-specific antagonist, GW9662, suggesting that rosiglitazone exerts this effect by activating the PPAR-␥ pathway. Furthermore, the Cterminal-truncated fragment of apoE4 significantly decreased dendritic spine density. Rosiglitazone rescued this detrimental effect. Thus, rosiglitazone might improve cognition in AD patients by increasing dendritic spine density.

Research paper thumbnail of Ducky mouse phenotype of epilepsy and ataxia is associated with mutations in the Cacna2d2 gene and decreased calcium channel current in cerebellar Purkinje cells

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 2001

The mouse mutant ducky, a model for absence epilepsy, is characterized by spike-wave seizures and... more The mouse mutant ducky, a model for absence epilepsy, is characterized by spike-wave seizures and ataxia. The ducky gene was mapped previously to distal mouse chromosome 9. High-resolution genetic and physical mapping has resulted in the identification of the Cacna2d2 gene encoding the alpha2delta2 voltage-dependent calcium channel subunit. Mutations in Cacna2d2 were found to underlie the ducky phenotype in the original ducky (du) strain and in a newly identified strain (du(2J)). Both mutations are predicted to result in loss of the full-length alpha2delta2 protein. Functional analysis shows that the alpha2delta2 subunit increases the maximum conductance of the alpha1A/beta4 channel combination when coexpressed in vitro in Xenopus oocytes. The Ca(2+) channel current in acutely dissociated du/du cerebellar Purkinje cells was reduced, with no change in single-channel conductance. In contrast, no effect on Ca(2+) channel current was seen in cerebellar granule cells, results consistent ...

Research paper thumbnail of Arf4 Determines Dentate Gyrus-Mediated Pattern Separation by Regulating Dendritic Spine Development

PLoS ONE, 2012

The ability to distinguish between similar experiences is a critical feature of episodic memory a... more The ability to distinguish between similar experiences is a critical feature of episodic memory and is primarily regulated by the dentate gyrus (DG) region of the hippocampus. However, the molecular mechanisms underlying such pattern separation tasks are poorly understood. We report a novel role for the small GTPase ADP ribosylation factor 4 (Arf4) in controlling pattern separation by regulating dendritic spine development. Arf4 +/2 mice at 4-5 months of age display severe impairments in a pattern separation task, as well as significant dendritic spine loss and smaller miniature excitatory postsynaptic currents (mEPSCs) in granule cells of the DG. Arf4 knockdown also decreases spine density in primary neurons, whereas Arf4 overexpression promotes spine development. A constitutively active form of Arf4, Arf4-Q71L, promotes spine density to an even greater extent than wildtype Arf4, whereas the inactive Arf4-T31N mutant does not increase spine density relative to controls. Arf49s effects on spine development are regulated by ASAP1, a GTPase-activating protein that modulates Arf4 GTPase activity. ASAP1 overexpression decreases spine density, and this effect is partially rescued by concomitant overexpression of wildtype Arf4 or Arf4-Q71L. In addition, Arf4 overexpression rescues spine loss in primary neurons from an Alzheimer's disease-related apolipoprotein (apo) E4 mouse model. Our findings suggest that Arf4 is a critical modulator of DG-mediated pattern separation by regulating dendritic spine development.

Research paper thumbnail of Intron-3 Retention/Splicing Controls Neuronal Expression of Apolipoprotein E in the CNS

Journal of Neuroscience, 2008

Neuronal expression of apolipoprotein (apo) E4 may contribute to the pathogenesis of Alzheimer&am... more Neuronal expression of apolipoprotein (apo) E4 may contribute to the pathogenesis of Alzheimer's disease (AD). In studying how apoE expression is regulated in neurons, we identified a splicing variant of apoE mRNA with intron-3 retention (apoE-I3). ApoE-I3 mRNA was detected in neuronal cell lines and primary neurons, but not in astrocytic cell lines or primary astrocytes, from humans and mice by reverse transcription (RT)-PCR. In both wild-type and human apoE knock-in mice, apoE-I3 was found predominantly in cortical and hippocampal neurons by in situ hybridization. Cell fractionation and quantitative RT-PCR revealed that over 98% of the apoE-I3 mRNA was retained in the nucleus without protein translation. In transfected primary neurons, apoE expression increased dramatically when intron-3 was deleted from a genomic DNA construct and decreased markedly when intron-3 was inserted into a cDNA construct, suggesting that intron-3 retention/splicing controls apoE expression in neurons. In response to excitotoxic challenge, the apoE-I3 mRNA was markedly increased in morphologically normal hippocampal neurons but reduced in degenerating hippocampal neurons in mice; apoE mRNA showed the opposite pattern. This apparent precursor-product relationship between apoE-I3 and apoE mRNA was supported by a transcriptional inhibition study. Thus, neuronal expression of apoE is controlled by transcription of apoE-I3 under normal conditions and by processing of apoE-I3 into mature apoE mRNA in response to injury.

Research paper thumbnail of Tau Reduction Prevents A -Induced Defects in Axonal Transport

Science, 2010

Amyloid-b (Ab) peptides, derived from the amyloid precursor protein, and the microtubule-associat... more Amyloid-b (Ab) peptides, derived from the amyloid precursor protein, and the microtubule-associated protein tau are key pathogenic factors in Alzheimer's disease (AD). How exactly they impair cognitive functions is unknown. We assessed the effects of Ab and tau on axonal transport of mitochondria and the neurotrophin receptor TrkA, cargoes that are critical for neuronal function and survival and whose distributions are altered in AD. Ab oligomers rapidly inhibited axonal transport of these cargoes in wild-type neurons. Lowering tau levels prevented these defects without affecting baseline axonal transport. Thus, Ab requires tau to impair axonal transport, and tau reduction protects against Ab-induced axonal transport defects.

Research paper thumbnail of Rosiglitazone increases dendritic spine density and rescues spine loss caused by apolipoprotein E4 in primary cortical neurons

Proceedings of the National Academy of Sciences, 2008

Convergent evidence has revealed an association between insulin resistance and Alzheimer's diseas... more Convergent evidence has revealed an association between insulin resistance and Alzheimer's disease (AD), and the peroxisome proliferator-activated receptor-␥ (PPAR-␥) agonist, rosiglitazone, an insulin sensitizer and mitochondrial activator, improves cognition in patients with early or mild-to-moderate AD. Apolipoprotein (apo) E4, a major genetic risk factor for AD, exerts neuropathological effects through multiple pathways, including impairment of dendritic spine structure and mitochondrial function. Here we show that rosiglitazone significantly increased dendritic spine density in a dose-dependent manner in cultured primary cortical rat neurons. This effect was abolished by the PPAR-␥-specific antagonist, GW9662, suggesting that rosiglitazone exerts this effect by activating the PPAR-␥ pathway. Furthermore, the Cterminal-truncated fragment of apoE4 significantly decreased dendritic spine density. Rosiglitazone rescued this detrimental effect. Thus, rosiglitazone might improve cognition in AD patients by increasing dendritic spine density.

Research paper thumbnail of Small Molecule Structure Correctors Abolish Detrimental Effects of Apolipoprotein E4 in Cultured Neurons

Journal of Biological Chemistry, 2012

Background: Apolipoprotein E4 (apoE4), the major gene involved in Alzheimer disease, has a unique... more Background: Apolipoprotein E4 (apoE4), the major gene involved in Alzheimer disease, has a unique structure, intramolecular domain interaction, that is associated with neuropathology. Results: Potent small molecule structure correctors block apoE4 domain interaction and reverse apoE4 detrimental effects in cultured neurons. Conclusion: Structure correctors negate the detrimental effects of apoE4 in neurons. Significance: ApoE4 structure correctors could represent a therapeutic approach for treating apoE4-associated neuropathology.

Research paper thumbnail of Structure-dependent Impairment of Intracellular Apolipoprotein E4 Trafficking and Its Detrimental Effects Are Rescued by Small-molecule Structure Correctors

Journal of Biological Chemistry, 2011

Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer disease (AD) and likely co... more Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer disease (AD) and likely contributes to neuropathology through various pathways. Here we report that the intracellular trafficking of apoE4 is impaired in Neuro-2a cells and primary neurons, as shown by measuring fluorescence recovery after photobleaching. In Neuro-2a cells, more apoE4 than apoE3 molecules remained immobilized in the endoplasmic reticulum (ER) and the Golgi apparatus, and the lateral motility of apoE4 was significantly lower in the Golgi apparatus (but not in the ER) than that of apoE3. Likewise, the immobile fraction was larger, and the lateral motility was lower for apoE4 than apoE3 in mouse primary hippocampal neurons. ApoE4 with the R61T mutation, which abolishes apoE4 domain interaction, was less immobilized, and its lateral motility was comparable with that of apoE3. The trafficking impairment of apoE4 was also rescued by disrupting domain interaction with the small-molecule structure correctors GIND25 and PH002. PH002 also rescued apoE4-induced impairments of neurite outgrowth in Neuro-2a cells and dendritic spine development in primary neurons. ApoE4 did not affect trafficking of amyloid precursor protein, another AD-related protein, through the secretory pathway. Thus, domain interaction renders more newly synthesized apoE4 molecules immobile and slows their trafficking along the secretory pathway. Correcting the pathological structure of apoE4 by disrupting domain interaction is a potential therapeutic approach to treat or prevent AD related to apoE4.

Research paper thumbnail of The Ducky Mutation in Cacna2d2 Results in Altered Purkinje Cell Morphology and Is Associated with the Expression of a Truncated alpha 2delta -2 Protein with Abnormal Function

Journal of Biological Chemistry, 2002

The mouse mutant ducky, a model for absence epilepsy, is characterized by spike-wave seizures and... more The mouse mutant ducky, a model for absence epilepsy, is characterized by spike-wave seizures and cerebellar ataxia. A mutation in Cacna2d2, the gene encoding the ␣2␦-2 voltage-dependent calcium channel accessory subunit, has been found to underlie the ducky phenotype. The ␣2␦-2 mRNA is strongly expressed in cerebellar Purkinje cells. We show that du/du mice have abnormalities in their Purkinje cell dendritic tree. The mutation in ␣2␦-2 results in the introduction of a premature stop codon and predicts the expression of a truncated protein encoded by the first three exons of Cacna2d2, followed by 8 novel amino acids. We show that both mRNA and protein corresponding to this predicted transcript are expressed in du/du cerebellum and present in Purkinje cells. Whereas the ␣2␦-2 subunit increased the peak current density of the Ca V 2.1/␤ 4 channel combination when co-expressed in vitro, co-expression with the truncated mutant ␣2␦-2 protein reduced current density, indicating that it may contribute to the du phenotype.

Research paper thumbnail of Apolipoprotein E4 impairs mitochondrial function and increases reactive oxygen species in neuronal cells

Alzheimer's & Dementia, 2009

Research paper thumbnail of Arf4 regulates dendritic spine development in mouse primary neurons

Alzheimer's & Dementia, 2010

co-immunoprecipitated with DISC1 at the endogenous protein level. Knockdown of DISC1 (lentivirus-... more co-immunoprecipitated with DISC1 at the endogenous protein level. Knockdown of DISC1 (lentivirus-mediated shRNA to DISC1) in mature primary cortical neurons, elicited no change in the levels of full-length APP (both mature and immature isoforms). In contrast, knockdown of DISC1 led to a significant increase in the levels of intracellular APP-C-terminal fragments C83 and C99. Knockdown of DISC1 also significantly enhanced sAPPa levels. Interestingly, we observed that DISC1 knockdown significantly decreased the levels of Ab42 and Ab40. The knockdown effects of DISC1 by RNAi on APP-CTFs, sAPPa and Ab 42/40 were successfully rescued by co-expression of wild-type DISC1. In the next step, we addressed whether DISC1 influences APP processing by using DISC1 knockout (KO) mice. We observed a significant increase in both C83 and C99 APP CTFs, with no change in the total APP levels in the DISC1 KO mice, as was the case in the primary neurons. Conclusions: DISC1 affects the processing of APP and generation of Ab in primary neuron cultures. Our goal is to characterize a novel mechanism of the regulation of APP processing/metabolism by DISC1.

Research paper thumbnail of O3-03-03: Apolipoprotein E4 and its fragment impair mitochondrial dynamics in neuronal cultures

Alzheimer's & Dementia, 2008

Research paper thumbnail of Effect of selective LRRK2 kinase inhibition on nonhuman primate lung

Science translational medicine, Jan 4, 2015

Inhibition of the kinase activity of leucine-rich repeat kinase 2 (LRRK2) is under investigation ... more Inhibition of the kinase activity of leucine-rich repeat kinase 2 (LRRK2) is under investigation as a possible treatment for Parkinson's disease. However, there is no clinical validation as yet, and the safety implications of targeting LRRK2 kinase activity are not well understood. We evaluated the potential safety risks by comparing human and mouse LRRK2 mRNA tissue expression, by analyzing a Lrrk2 knockout mouse model, and by testing selective brain-penetrating LRRK2 kinase inhibitors in multiple species. LRRK2 mRNA tissue expression was comparable between species. Phenotypic analysis of Lrrk2 knockout mice revealed morphologic changes in lungs and kidneys, similar to those reported previously. However, in preclinical toxicity assessments in rodents, no pulmonary or renal changes were induced by two distinct LRRK2 kinase inhibitors. Both of these kinase inhibitors induced abnormal cytoplasmic accumulation of secretory lysosome-related organelles known as lamellar bodies in typ...