title: WNK1 phosphorylates synaptotagmin 2 and modulates its membrane binding.
abstract: WNK (with no lysine [K]) protein kinases were named for their unique active site organization. Mutations in WNK1 and WNK4 cause a familial form of hypertension by undefined mechanisms. Here, we report that WNK1 selectively binds to and phosphorylates synaptotagmin 2 (Syt2) within its calcium binding C2 domains. Endogenous WNK1 and Syt2 coimmunoprecipitate and colocalize on a subset of secretory granules in INS-1 cells. Phosphorylation by WNK1 increases the amount of Ca2+ required for Syt2 binding to phospholipid vesicles; mutation of threonine 202, a WNK1 phosphorylation site, partially prevents this change. These findings suggest that phosphorylation of Syts by WNK1 can regulate Ca2+ sensing and the subsequent Ca2+-dependent interactions mediated by Syt C2 domains. These findings provide a biochemical mechanism that could lead to the retention or insertion of proteins in the plasma membrane. Interruption of this regulatory pathway may disturb membrane events that regulate ion balance.
authors.affiliation: Department of Pharmacology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
authors.forename: Byung-Hoon
authors.initials: BH
authors.lastname: Lee
authors.forename: Xiaoshan
authors.initials: X
authors.lastname: Min
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Heise
authors.forename: Bing-E
authors.initials: BE
authors.lastname: Xu
authors.forename: She
authors.initials: S
authors.lastname: Chen
authors.forename: Hongjun
authors.initials: H
authors.lastname: Shu
authors.forename: Kate
authors.initials: K
authors.lastname: Luby-Phelps
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Goldsmith
authors.forename: Melanie H
authors.initials: MH
authors.lastname: Cobb
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000502:physiology; D020013:Calcium Signaling / Q000235:genetics; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D015778:Minor Histocompatibility Antigens; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D022142:Secretory Vesicles / Q000378:metabolism; D050861:Synaptotagmin II; D013912:Threonine / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D000076204:WNK Lysine-Deficient Protein Kinase 1; D014882:Water-Electrolyte Balance
chemical_list: D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015778:Minor Histocompatibility Antigens; D009419:Nerve Tissue Proteins; C494262:SYT2 protein, human; D050861:Synaptotagmin II; D013912:Threonine; D017346:Protein Serine-Threonine Kinases; D000076204:WNK Lysine-Deficient Protein Kinase 1; C498743:WNK1 protein, human