Combining Valosin-containing Protein (VCP) Inhibition and Suberanilohydroxamic Acid (SAHA) Treatment Additively Enhances the Folding, Trafficking, and Function of Epilepsy-associated γ-Aminobutyric Acid, Type A (GABAA) Receptors

• Published in: The Journal of biological chemistry Vol. 290; no. 1; pp. 325 - 337
• Main Authors: Han, Dong-Yun, Di, Xiao-Jing, Fu, Yan-Lin, Mu, Ting-Wei
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 02.01.2015; American Society for Biochemistry and Molecular Biology
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Adenosine Triphosphatases - antagonists & inhibitors; Adenosine Triphosphatases - genetics; Adenosine Triphosphatases - metabolism; Adolescent; Cell Cycle Proteins - antagonists & inhibitors; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell Line, Tumor; Chlorides - metabolism; Drug Synergism; Dynamin I - genetics; Dynamin I - metabolism; Endocytosis - drug effects; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - metabolism; Endoplasmic Reticulum-Associated Degradation - drug effects; Endoplasmic Reticulum-Associated Degradation - genetics; Epilepsy; ER Quality Control; ER-associated Degradation; GABA Receptor; gamma-Aminobutyric Acid - metabolism; HEK293 Cells; Humans; Hydrazones - pharmacology; Hydroxamic Acids - pharmacology; Hydroxyurea - analogs & derivatives; Hydroxyurea - pharmacology; Myoclonic Epilepsy, Juvenile - genetics; Myoclonic Epilepsy, Juvenile - metabolism; Myoclonic Epilepsy, Juvenile - pathology; Neurons - drug effects; Neurons - metabolism; Neurons - pathology; Patch-Clamp Techniques; Proteasome Endopeptidase Complex - drug effects; Proteasome Endopeptidase Complex - metabolism; Protein Folding - drug effects; Protein Misfolding; Protein Stability - drug effects; Protein Synthesis and Degradation; Proteostasis; Receptors, GABA-A - chemistry; Receptors, GABA-A - genetics; Receptors, GABA-A - metabolism; SAHA; Signal Transduction; Valosin Containing Protein; VCP; Vorinostat; Protein Misfolding; SAHA; VCP; ER Quality Control; Proteostasis; Epilepsy; GABA Receptor; ER-associated Degradation
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M114.580324

GABAA receptors are the primary inhibitory ion channels in the mammalian central nervous system. The A322D mutation in the α1 subunit results in its excessive endoplasmic reticulum-associated degradation at the expense of plasma membrane trafficking, leading to autosomal dominant juvenile myoclonic epilepsy. Presumably, valosin-containing protein (VCP)/p97 extracts misfolded subunits from the endoplasmic reticulum membrane to the cytosolic proteasome for degradation. Here we showed that inhibiting VCP using Eeyarestatin I reduces the endoplasmic reticulum-associated degradation of the α1(A322D) subunit without an apparent effect on its dynamin-1 dependent endocytosis and that this treatment enhances its trafficking. Furthermore, coapplication of Eeyarestatin I and suberanilohydroxamic acid, a known small molecule that promotes chaperone-assisted folding, yields an additive restoration of surface expression of α1(A322D) subunits in HEK293 cells and neuronal SH-SY5Y cells. Consequently, this combination significantly increases GABA-induced chloride currents in whole-cell patch clamping experiments than either chemical compound alone in HEK293 cells. Our findings suggest that VCP inhibition without stress induction, together with folding enhancement, represents a new strategy to restore proteostasis of misfolding-prone GABAA receptors and, therefore, a potential remedy for idiopathic epilepsy.The α1 subunit harboring the A322D mutation is subject to excessive ERAD. VCP inhibition using Eeyarestatin I reduces the ERAD of α1(A322D) subunits, and coapplication of SAHA additively enhances their proteostasis. Combining ERAD inhibition and folding enhancement yields significant functional rescue. This combination represents a new, promising strategy to treat epilepsy resulting from GABAA receptor misfolding.