title: Channel-anchored protein kinase CK2 and protein phosphatase 1 reciprocally regulate KCNQ2-containing M-channels via phosphorylation of calmodulin.
abstract: M-type potassium channels, encoded by the KCNQ family genes (KCNQ2-5), require calmodulin as an essential co-factor. Calmodulin bound to the KCNQ2 subunit regulates channel trafficking and stabilizes channel activity. We demonstrate that phosphorylation of calmodulin by protein kinase CK2 (casein kinase 2) rapidly and reversibly modulated KCNQ2 current. CK2-mediated phosphorylation of calmodulin strengthened its binding to KCNQ2 channel, caused resistance to phosphatidylinositol 4,5-bisphosphate depletion, and increased KCNQ2 current amplitude. Accordingly, application of CK2-selective inhibitors suppressed KCNQ2 current. This suppression was prevented by co-expression of CK2 phosphomimetic calmodulin mutants or pretreatment with a protein phosphatase inhibitor, calyculin A. We also demonstrated that functional CK2 and protein phosphatase 1 (PP1) were selectively tethered to the KCNQ2 subunit. We identified a functional KVXF consensus site for PP1 binding in the N-terminal tail of KCNQ2 subunit: mutation of this site augmented current density. CK2 inhibitor treatment suppressed M-current in rat superior cervical ganglion neurons, an effect negated by overexpression of phosphomimetic calmodulin or pretreatment with calyculin A Furthermore, CK2 inhibition diminished the medium after hyperpolarization by suppressing the M-current. These findings suggest that CK2-mediated phosphorylation of calmodulin regulates the M-current, which is tonically regulated by CK2 and PP1 anchored to the KCNQ2 channel complex.
authors.affiliation: Departments of Pharmacology and University of California, Irvine, California 92697.
authors.forename: Seungwoo
authors.initials: S
authors.lastname: Kang
authors.affiliation: Departments of Neurology and Baylor College of Medicine, Houston, Texas 77030.
authors.forename: Mingxuan
authors.initials: M
authors.lastname: Xu
authors.affiliation: Departments of Neurology and Baylor College of Medicine, Houston, Texas 77030; Departments of Neuroscience, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Cooper
authors.affiliation: Departments of Pharmacology and University of California, Irvine, California 92697; Departments of Physiology and Biophysics, University of California, Irvine, California 92697 and. Electronic address: nhoshi@uci.edu.
authors.forename: Naoto
authors.initials: N
authors.lastname: Hoshi
mesh_terms: D000818:Animals; D016466:CHO Cells; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism*; D047390:Casein Kinase II / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051658:KCNQ2 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D008387:Marine Toxins; D009154:Mutation; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology; D054645:Protein Phosphatase 1 / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D004791:Enzyme Inhibitors; D051658:KCNQ2 Potassium Channel; C496915:Kcnq2 protein, rat; D008387:Marine Toxins; D010080:Oxazoles; C059041:calyculin A; D047390:Casein Kinase II; D054645:Protein Phosphatase 1
keywords: CK2; Calmodulin; KCNQ2; PP1; Potassium Channels; Protein Kinases; Protein Phosphorylation