Ubiquitin-proteasome dependent degradation of GABAAα1 in autism spectrum disorderReport as inadecuate




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Molecular Autism

, 5:45

First Online: 01 September 2014Received: 19 June 2014Accepted: 11 August 2014

Abstract

BackgroundAlthough 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 mechanisms of regulation of GABAA receptors in ASD remains poorly understood.

MethodsPostmortem 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.

ResultsA significant decrease in GABAAα1 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 GABAAα1 protein levels and Lys48-linked polyubiquitination of GABAAα1, but reduced proteasome activity in mouse primary cortical neurons DIV 14 from E16 embryos. Moreover, treatment with betulinic acid, a proteasome activator significantly decreased GABAAα1 protein levels in cortical neurons indicating the role of polyubiquitination of GABAAα1 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 GABAAα1 in the ER. The siRNA knockdown of SYVN1 significantly increased GABAAα1 protein levels in cortical neurons. Moreover, reduced association between SYVN1 and GABAAα1 was found in the middle frontal gyrus of ASD subjects.

ConclusionsSYVN1 plays a critical role as an E3 ligase in the ubiquitin proteasome system UPS-mediated GABAAα1 degradation. Thus, inhibition of the ubiquitin-proteasome-mediated GABAAα1 degradation may be an important mechanism for preventing GABAAα1 turnover to maintain GABAAα1 levels and GABA signaling in ASD.

KeywordsAutism GABAA receptor Ubiquitination SYVN1 Neurons AbbreviationsADI-RAutism diagnostic interview revised

ASDAutism spectrum disorders

ERADEndoplasmic-reticulum-associated protein degradation GABA, γ-amino butyric acid

SYVN1Synovial apoptosis inhibitor 1

UPSUbiquitin-proteasome system.

Electronic supplementary materialThe online version of this article doi:10.1186-2040-2392-5-45 contains supplementary material, which is available to authorized users.

Amanda Crider, Chirayu D Pandya contributed equally to this work.

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Author: Amanda Crider - Chirayu D Pandya - Diya Peter - Anthony O Ahmed - Anilkumar Pillai

Source: https://link.springer.com/







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