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Ubiquitin-proteasome dependent degradation of GABAA?1 in autism spectrum disorder.

ABSTRACT: Although the neurobiological basis of autism spectrum disorder (ASD) is not fully understood, recent studies have indicated the potential role of GABAA receptors in the pathophysiology of ASD. GABAA receptors play a crucial role in various neurodevelopmental processes and adult neuroplasticity. However, the mechanism(s) of regulation of GABAA receptors in ASD remains poorly understood.Postmortem middle frontal gyrus tissues (13 ASD and 13 control subjects) were used. In vitro studies were performed in primary cortical neurons at days in vitro (DIV) 14. The protein levels were examined by western blotting. Immunofluorescence studies were employed for cellular localization. The gene expression was determined by RT-PCR array and qRT-PCR.A significant decrease in GABAA?1 protein, but not mRNA levels was found in the middle frontal gyrus of ASD subjects indicating a post-translational regulation of GABAA receptors in ASD. At the cellular level, treatment with proteasomal inhibitor, MG132, or lactacystin significantly increased GABAA?1 protein levels and Lys48-linked polyubiquitination of GABAA?1, but reduced proteasome activity in mouse primary cortical neurons (DIV 14 from E16 embryos). Moreover, treatment with betulinic acid, a proteasome activator significantly decreased GABAA?1 protein levels in cortical neurons indicating the role of polyubiquitination of GABAA?1 proteins with their subsequent proteasomal degradation in cortical neurons. Ubiquitination specific RT-PCR array followed by western blot analysis revealed a significant increase in SYVN1, an endoplasmic reticulum (ER)-associated degradation (ERAD) E3 ubiquitin ligase in the middle frontal gyrus of ASD subjects. In addition, the inhibition of proteasomal activity by MG132 increased the expression of GABAA?1 in the ER. The siRNA knockdown of SYVN1 significantly increased GABAA?1 protein levels in cortical neurons. Moreover, reduced association between SYVN1 and GABAA?1 was found in the middle frontal gyrus of ASD subjects.SYVN1 plays a critical role as an E3 ligase in the ubiquitin proteasome system (UPS)-mediated GABAA?1 degradation. Thus, inhibition of the ubiquitin-proteasome-mediated GABAA?1 degradation may be an important mechanism for preventing GABAA?1 turnover to maintain GABAA?1 levels and GABA signaling in ASD.

SUBMITTER: Crider A

PROVIDER: S-EPMC4228821 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Ubiquitin-proteasome dependent degradation of GABAAα1 in autism spectrum disorder.

Crider Amanda A Pandya Chirayu D CD Peter Diya D Ahmed Anthony O AO Pillai Anilkumar A

Molecular autism 20140901

<h4>Background</h4>Although the neurobiological basis of autism spectrum disorder (ASD) is not fully understood, recent studies have indicated the potential role of GABAA receptors in the pathophysiology of ASD. GABAA receptors play a crucial role in various neurodevelopmental processes and adult neuroplasticity. However, the mechanism(s) of regulation of GABAA receptors in ASD remains poorly understood.<h4>Methods</h4>Postmortem middle frontal gyrus tissues (13 ASD and 13 control subjects) were ...[more]

PMID: 25392730

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Project description:Disruption of the GABAergic system has been implicated in multiple developmental disorders, including epilepsy, autism spectrum disorder and schizophrenia. The human gene encoding uPAR (PLAUR) has been shown recently to be associated with the risk of autism. The uPAR(-/-) mouse exhibits a regionally-selective reduction in GABAergic interneurons in frontal and parietal regions of the cerebral cortex as well as in the CA1 and dentate gyrus subfields of the hippocampus. Behaviorally, these mice exhibit increased sensitivity to pharmacologically-induced seizures, heightened anxiety, and atypical social behavior. Here, we explore potential alterations in GABAergic circuitry that may occur in the context of altered interneuron development. Analysis of gene expression for 13 GABA(A) receptor subunits using quantitative real-time polymerase chain reaction (PCR) indicates seven subunit mRNAs (alpha(1), alpha(2), alpha(3), beta(2), beta(3), gamma(2S) and gamma(2L)) of interest. Semi-quantitative in situ hybridization analysis focusing on these subunit mRNAs reveals a complex pattern of potential gene regulatory adaptations. The levels of alpha(2) subunit mRNAs increase in frontal cortex, CA1 and CA3, while those of alpha3 decrease in frontal cortex and CA1. In contrast, alpha(1) subunit mRNAs are unaltered in any region examined. beta(2) subunit mRNAs are increased in frontal cortex whereas beta(3) subunit mRNAs are decreased in parietal cortex. Finally, gamma(2S) subunit mRNAs are increased in parietal cortex while gamma(2L) subunit mRNAs are increased in the dentate gyrus, potentially altering the gamma(2S):gamma(2L) ratio in these two regions. For all subunits, no changes were observed in forebrain regions where GABAergic interneuron numbers are normal. We propose that disrupted differentiation of GABAergic neurons specifically in frontal and parietal cortices leads to regionally-selective alterations in local circuitry and subsequent adaptive changes in receptor subunit composition. Future electrophysiological studies will be useful in determining how alterations in network activity in the cortex and hippocampus relate to the observed behavioral phenotype.

Dataset Information

Ubiquitin-proteasome dependent degradation of GABAA?1 in autism spectrum disorder.

Publications

Ubiquitin-proteasome dependent degradation of GABAAα1 in autism spectrum disorder.

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