title: S-acylation regulates Kv1.5 channel surface expression.
abstract: The number of ion channels expressed on the cell surface shapes the complex electrical response of excitable cells. An imbalance in the ratio of inward and outward conducting channels is unfavorable and often detrimental. For example, over- or underexpression of voltage-gated K(+) (Kv) channels can be cytotoxic and in some cases lead to disease. In this study, we demonstrated a novel role for S-acylation in Kv1.5 cell surface expression. In transfected fibroblasts, biochemical evidence showed that Kv1.5 is posttranslationally modified on both the NH(2) and COOH termini via hydroxylamine-sensitive thioester bonds. Pharmacological inhibition of S-acylation, but not myristoylation, significantly decreased Kv1.5 expression and resulted in accumulation of channel protein in intracellular compartments and targeting for degradation. Channel protein degradation was rescued by treatment with proteasome inhibitors. Time course experiments revealed that S-acylation occurred in the biosynthetic pathway of nascent channel protein and showed that newly synthesized Kv1.5 protein, but not protein expressed on the cell surface, is sensitive to inhibitors of thioacylation. Sensitivity to inhibitors of S-acylation was governed by COOH-terminal, but not NH(2)-terminal, cysteines. Surprisingly, although intracellular cysteines were required for S-acylation, mutation of these residues resulted in an increase in Kv1.5 cell surface channel expression, suggesting that screening of free cysteines by fatty acylation is an important regulatory step in the quality control pathway. Together, these results show that S-acylation can regulate steady-state expression of Kv1.5.
authors.affiliation: Dept. of Pharmacology, University of Michigan, 1150 W. Medical Center Dr., 1301 MSRB III, Ann Arbor, MI 48109-0632, USA.
authors.forename: Lian
authors.initials: L
authors.lastname: Zhang
authors.forename: Karyn
authors.initials: K
authors.lastname: Foster
authors.forename: Qiuju
authors.initials: Q
authors.lastname: Li
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Martens
mesh_terms: D000215:Acylation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002569:Cerulenin / Q000494:pharmacology; D003545:Cysteine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D019811:Hydroxylamine / Q000494:pharmacology; D015640:Ion Channel Gating; D051666:Kv1.5 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010168:Palmitates / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: D005227:Fatty Acids; C496981:KCNA5 protein, human; D051666:Kv1.5 Potassium Channel; D010168:Palmitates; D013438:Sulfhydryl Compounds; D002569:Cerulenin; C022776:2-bromopalmitate; D019811:Hydroxylamine; D046988:Proteasome Endopeptidase Complex; D003545:Cysteine