Quantitative interactome proteomics identifies a proteostasis network for GABA_A receptors

Area of Science:

• Neuroscience
• Molecular Biology
• Proteomics

Background:

• Gamma-aminobutyric acid type A (GABA_A) receptors are crucial for inhibitory neurotransmission in the central nervous system.
• Maintaining GABA_A receptor protein homeostasis is vital for neuronal function, but the underlying mechanisms are not fully understood.

Purpose of the Study:

• To systematically identify proteins interacting with GABA_A receptors using a proteomics approach.
• To understand the role of the proteostasis network in GABA_A receptor biogenesis, folding, trafficking, and degradation.
• To investigate the specific role of TRIM21 in regulating GABA_A receptor subunit degradation.

Main Methods:

• Quantitative immunoprecipitation-tandem mass spectrometry (IP-MS) with stable isotope labeling by amino acids in cell culture.
• Comparative proteomics using wild-type and misfolding-prone GABA_A receptor α1 subunits.
• Bioinformatics analysis to identify proteostasis network components.
• Co-immunoprecipitation assays in mouse brain homogenates.

Main Results:

• Identified 125 interactors for wild-type α1-containing receptors and 105 for the misfolding-prone α1(A322D) variant.
• Discovered 54 overlapping proteins involved in GABA_A receptor proteostasis, including chaperones, folding enzymes, and degradation factors.
• Confirmed endogenous interactions and demonstrated that TRIM21 selectively targets misfolding-prone α1(A322D) subunits for degradation.

Conclusions:

• The study provides a comprehensive interactome map of GABA_A receptors, elucidating their proteostasis network.
• The findings offer insights into the molecular mechanisms governing GABA_A receptor biogenesis and quality control.
• Targeting the identified proteostasis factors, like TRIM21, may offer therapeutic strategies for neurological diseases associated with GABA_A receptor dysfunction.