title: Translocation of telokin by cGMP signaling in smooth muscle cells.
abstract: Telokin is an acidic protein with a sequence identical to the COOH-terminal domain of myosin light chain kinase (MLCK) produced by an alternate promoter of the MLCK gene. Although it is abundantly expressed in smooth muscle, its physiological function is not understood. In the present study, we attempted to clarify the function of telokin by analyzing its spatial and temporal localization in living single smooth muscle cells. Primary cultured smooth muscle cells were transfected with green fluorescent protein (GFP)-tagged telokin. The telokin-GFP localized mostly diffusely in cytosol. Stimulation with both sodium nitroprusside (SNP) and 8-bromo-cyclic GMP induced translocation of GFP-tagged telokin to near plasma membrane in living single smooth muscle cells. The translocation was slow, and it took more than 10 min at room temperature. Mutation of the phosphorylation sites of telokin (S13A, S19A, and S13A/S19A) significantly attenuated SNP-induced translocation. Both KT-5823 (cGMP-dependent protein kinase inhibitor) and PD-98059 (mitogen-activated protein kinase inhibitor) diminished the telokin-GFP translocation. These results suggest that telokin changes its intracellular localization because of phosphorylation at Ser13 and/or Ser19 via the cGMP-signaling pathway.
authors.affiliation: Department of Physiology, University of Massachusetts Medical School, Worcester 01655, USA.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Komatsu
authors.forename: Koji
authors.initials: K
authors.lastname: Miyazaki
authors.forename: Richard A
authors.initials: RA
authors.lastname: Tuft
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ikebe
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000502:physiology; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009219:Myosin-Light-Chain Kinase; D009218:Myosins / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010446:Peptide Fragments; D010455:Peptides; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D014132:Trachea; D014162:Transfection
chemical_list: D004791:Enzyme Inhibitors; D008164:Luminescent Proteins; D009124:Muscle Proteins; D020030:Nitric Oxide Donors; D010446:Peptide Fragments; D010455:Peptides; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C016276:8-bromocyclic GMP; C060640:telokin; D017869:Cyclic GMP-Dependent Protein Kinases; D009219:Myosin-Light-Chain Kinase; D009218:Myosins; D006152:Cyclic GMP