Palmitoylation of the S0-S1 Linker Regulates Cell Surface Expression of Voltage- and Calcium-activated Potassium (BK) Channels

• Published in: The Journal of biological chemistry 2010-10, Vol.285 (43), p.33307-33314
• Main Authors: Jeffries, Owen, Geiger, Nina, Rowe, Iain C.M., Tian, Lijun, McClafferty, Heather, Chen, Lie, Bi, Danlei, Knaus, Hans Guenther, Ruth, Peter, Shipston, Michael J.
• Format: Article
• Language: English
• Subjects: Alternative Splicing - physiology; Amino Acid Substitution; Animals; Cell Line; Cell Membrane - genetics; Cell Membrane - metabolism; Gene Expression Regulation - physiology; Humans; Ion Channels; Large-Conductance Calcium-Activated Potassium Channels - biosynthesis; Large-Conductance Calcium-Activated Potassium Channels - genetics; Membrane Biology; Membrane Proteins; Membrane Trafficking; Mice; Mutation, Missense; Palmitic Acid - metabolism; Potassium Channels; Protein Palmitoylation; Protein Processing, Post-Translational - physiology; Protein Structure, Tertiary; Signal Transduction
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M110.153940

S-Palmitoylation is rapidly emerging as an important post-translational mechanism to regulate ion channels. We have previously demonstrated that large conductance calcium- and voltage-activated potassium (BK) channels are palmitoylated within an alternatively spliced (STREX) insert. However, these studies also revealed that additional site(s) for palmitoylation must exist outside of the STREX insert, although the identity or the functional significance of these palmitoylated cysteine residues are unknown. Here, we demonstrate that BK channels are palmitoylated at a cluster of evolutionary conserved cysteine residues (Cys-53, Cys-54, and Cys-56) within the intracellular linker between the S0 and S1 transmembrane domains. Mutation of Cys-53, Cys-54, and Cys-56 completely abolished palmitoylation of BK channels lacking the STREX insert (ZERO variant). Palmitoylation allows the S0-S1 linker to associate with the plasma membrane but has no effect on single channel conductance or the calcium/voltage sensitivity. Rather, S0-S1 linker palmitoylation is a critical determinant of cell surface expression of BK channels, as steady state surface expression levels are reduced by ∼55% in the C53:54:56A mutant. STREX variant channels that could not be palmitoylated in the S0-S1 linker also displayed significantly reduced cell surface expression even though STREX insert palmitoylation was unaffected. Thus our work reveals the functional independence of two distinct palmitoylation-dependent membrane interaction domains within the same channel protein and demonstrates the critical role of S0-S1 linker palmitoylation in the control of BK channel cell surface expression.