Palmitoylation gates phosphorylation-dependent regulation of BK potassium channels

• Published in: Proceedings of the National Academy of Sciences - PNAS 2008-12, Vol.105 (52), p.21006-21011
• Main Authors: Tian, Lijun, Jeffries, Owen, McClafferty, Heather, Molyvdas, Adam, Rowe, Iain C.M, Saleem, Fozia, Chen, Lie, Greaves, Jennifer, Chamberlain, Luke H, Knaus, Hans-Guenther, Ruth, Peter, Shipston, Michael J
• Format: Article
• Language: English
• Subjects: Animals; Biological Sciences; Cell Line; Cell Membrane - genetics; Cell Membrane - metabolism; Cell membranes; Cells; Cyclic AMP-Dependent Protein Kinases - genetics; Cyclic AMP-Dependent Protein Kinases - metabolism; Gene expression regulation; HEK293 cells; Homeostasis - physiology; Humans; Imaging; Ion channels; Kinases; Large conductance calcium activated potassium channels; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits - genetics; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits - metabolism; Membranes; Mice; Mutagenesis, Site-Directed - methods; Palmitic Acid - metabolism; Phosphorylation; Phosphorylation - physiology; Physiological regulation; Potassium; Potassium channels; Protein Processing, Post-Translational - physiology; Protein Structure, Tertiary - physiology; Proteins; Signal transduction; Signal Transduction - physiology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0806700106

Large conductance calcium- and voltage-gated potassium (BK) channels are important regulators of physiological homeostasis and their function is potently modulated by protein kinase A (PKA) phosphorylation. PKA regulates the channel through phosphorylation of residues within the intracellular C terminus of the pore-forming α-subunits. However, the molecular mechanism(s) by which phosphorylation of the α-subunit effects changes in channel activity are unknown. Inhibition of BK channels by PKA depends on phosphorylation of only a single α-subunit in the channel tetramer containing an alternatively spliced insert (STREX) suggesting that phosphorylation results in major conformational rearrangements of the C terminus. Here, we define the mechanism of PKA inhibition of BK channels and demonstrate that this regulation is conditional on the palmitoylation status of the channel. We show that the cytosolic C terminus of the STREX BK channel uniquely interacts with the plasma membrane via palmitoylation of evolutionarily conserved cysteine residues in the STREX insert. PKA phosphorylation of the serine residue immediately upstream of the conserved palmitoylated cysteine residues within STREX dissociates the C terminus from the plasma membrane, inhibiting STREX channel activity. Abolition of STREX palmitoylation by site-directed mutagenesis or pharmacological inhibition of palmitoyl transferases prevents PKA-mediated inhibition of BK channels. Thus, palmitoylation gates BK channel regulation by PKA phosphorylation. Palmitoylation and phosphorylation are both dynamically regulated; thus, cross-talk between these 2 major posttranslational signaling cascades provides a mechanism for conditional regulation of BK channels. Interplay of these distinct signaling cascades has important implications for the dynamic regulation of BK channels and physiological homeostasis.