title: 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.
abstract: 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.
authors.affiliation: From the Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106.
authors.forename: Dong-Yun
authors.initials: DY
authors.lastname: Han
authors.affiliation: From the Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106.
authors.forename: Xiao-Jing
authors.initials: XJ
authors.lastname: Di
authors.affiliation: From the Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106.
authors.forename: Yan-Lin
authors.initials: YL
authors.lastname: Fu
authors.affiliation: From the Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106 tingwei.mu@case.edu.
authors.forename: Ting-Wei
authors.initials: TW
authors.lastname: Mu
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000293:Adolescent; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D002712:Chlorides / Q000378:metabolism; D004357:Drug Synergism; D034284:Dynamin I / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D060746:Endoplasmic Reticulum-Associated Degradation / Q000187:drug effects* / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D006835:Hydrazones / Q000494:pharmacology*; D006877:Hydroxamic Acids / Q000494:pharmacology*; D006918:Hydroxyurea / Q000031:analogs & derivatives* / Q000494:pharmacology; D020190:Myoclonic Epilepsy, Juvenile / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018408:Patch-Clamp Techniques; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D017510:Protein Folding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D011963:Receptors, GABA-A / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000074405:Valosin Containing Protein; D000077337:Vorinostat; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: C492847:1-(4-chlorophenyl)-3-(3-(4-chlorophenyl)-5,5-dimethyl-1-(3-(5-nitrofuran-2-yl)allyldienehydrazinocarbonylmethyl)-2-oxoimidazolidin-4-yl)-1-hydroxyurea; D018797:Cell Cycle Proteins; D002712:Chlorides; D006835:Hydrazones; D006877:Hydroxamic Acids; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D000077337:Vorinostat; D046988:Proteasome Endopeptidase Complex; D034284:Dynamin I; D000251:Adenosine Triphosphatases; C000614178:VCP protein, human; D000074405:Valosin Containing Protein; D006918:Hydroxyurea
keywords: ER Quality Control; ER-associated Degradation; Epilepsy; GABA Receptor; Protein Misfolding; Proteostasis; SAHA; VCP