Manipulating the ERAD pathway to regulate GABAA receptor protein homeostasis

Abstract

GABAA (γ‐aminobutyric acid type A) receptors are major inhibitory ligand‐gated ion channels in the mammalian central nervous system. To function, GABAA receptors need to fold into their native structures, assemble correctly in the endoplasmic reticulum (ER), and traffic properly to plasma membrane. Terminally misfolded GABAA receptors are degraded through the ER associated protein degradation (ERAD) pathway. Extensive ERAD leads to loss of function of GABAA receptors, causing idiopathic epilepsy. We intend to manipulate the ERAD pathway to regulate GABAA receptor protein homeostasis in the cell, as a therapeutic strategy to ameliorate idiopathic epilepsy. A number of critical ERAD factors were enriched after the immunoprecipitation of GABAA receptors followed by affinity purification‐mass spectrometry analysis using HEK293 overexpressing GABAA receptors. Inhibition of critical ERAD factors increased the total protein expression level for both wild type α1β2γ2 and α1(A322D)β2γ2 GABAA receptors. However, trafficking and function of GABAA receptors were only enhanced with selective ERAD factor inhibition for α1(A322D)β2γ2 GABAA receptors. It appears that selective ERAD factor inhibition upregulates both cellular folding and cellular trafficking capacity. Manipulation of the ERAD pathway might be a general strategy to ameliorate a variety of ion channel misfolding diseases.