title: 14-3-3 and calmodulin control subcellular distribution of Kir/Gem and its regulation of cell shape and calcium channel activity.
abstract: Individual members of the RGK family of Ras-related GTPases, which comprise Rad, Gem/Kir, Rem and Rem2, have been implicated in important functions such as the regulation of voltage-gated calcium channel activity and remodeling of cell shape. The GTPase Kir/Gem inhibits the activity of calcium channels by interacting with the beta-subunit and also regulates cytoskeleton dynamics by inhibiting the Rho-Rho kinase pathway. In addition, Kir/Gem interacts with 14-3-3 and calmodulin, but the significance of this interaction on Kir/Gem function is poorly understood. Here, we present a comprehensive analysis of the binding of 14-3-3 and calmodulin to Kir/Gem. We show that 14-3-3, in conjunction with calmodulin, regulates the subcellular distribution of Kir/Gem between the cytoplasm and the nucleus. In addition, 14-3-3 and calmodulin binding modulate Kir/Gem-mediated cell shape remodeling and downregulation of calcium channel activity. Competition experiments show that binding of 14-3-3, calmodulin and calcium channel beta-subunits to Kir/Gem is mutually exclusive, providing a rationale for the observed regulatory effects of 14-3-3 and calmodulin on Kir/Gem localization and function.
authors.affiliation: Epithelial Cell Biology Laboratory, Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore 138673, Republic of Singapore. beguinp@imcb.a-star.edu.sg
authors.forename: Pascal
authors.initials: P
authors.lastname: Béguin
authors.forename: Ramasubbu N
authors.initials: RN
authors.lastname: Mahalakshmi
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Nagashima
authors.forename: Damian H K
authors.initials: DH
authors.lastname: Cher
authors.forename: Akira
authors.initials: A
authors.lastname: Takahashi
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Yamada
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Seino
authors.forename: Walter
authors.initials: W
authors.lastname: Hunziker
mesh_terms: D048948:14-3-3 Proteins / Q000502:physiology*; D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D019281:Dimerization; D004594:Electrophysiology; D020558:GTP Phosphohydrolases / Q000378:metabolism; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D017874:Immediate-Early Proteins / Q000096:biosynthesis*; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D020559:Monomeric GTP-Binding Proteins / Q000096:biosynthesis*; D009154:Mutation; D016716:PC12 Cells; D017354:Point Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D013347:Subcellular Fractions; D014162:Transfection
chemical_list: D048948:14-3-3 Proteins; D015220:Calcium Channels; D002147:Calmodulin; D018076:DNA, Complementary; D017874:Immediate-Early Proteins; D005982:Glutathione Transferase; D020558:GTP Phosphohydrolases; C490245:GEM protein, human; D020559:Monomeric GTP-Binding Proteins; C484604:Rem2 protein, rat; D002118:Calcium