title: Ca2+/Calmodulin and Apo-Calmodulin Both Bind to and Enhance the Tyrosine Kinase Activity of c-Src.
abstract: Src family non-receptor tyrosine kinases play a prominent role in multiple cellular processes, including: cell proliferation, differentiation, cell survival, stress response, and cell adhesion and migration, among others. And when deregulated by mutations, overexpression, and/or the arrival of faulty incoming signals, its hyperactivity contributes to the development of hematological and solid tumors. c-Src is a prototypical member of this family of kinases, which is highly regulated by a set of phosphorylation events. Other factor contributing to the regulation of Src activity appears to be mediated by the Ca2+ signal generated in cells by different effectors, where the Ca2+-receptor protein calmodulin (CaM) plays a key role. In this report we demonstrate that CaM directly interacts with Src in both Ca2+-dependent and Ca2+-independent manners in vitro and in living cells, and that the CaM antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) inhibits the activation of this kinase induced by the upstream activation of the epidermal growth factor receptor (EGFR), in human carcinoma epidermoide A431 cells, and by hydrogen peroxide-induced oxidative stress, in both A431 cells and human breast adenocarcinoma SK-BR-3 cells. Furthermore, we show that the Ca2+/CaM complex strongly activates the auto-phosphorylation and tyrosine kinase activity of c-Src toward exogenous substrates, but most relevantly and for the first time, we demonstrate that Ca2+-free CaM (apo-CaM) exerts a far higher activatory action on Src auto-phosphorylation and kinase activity toward exogenous substrates than the one exerted by the Ca2+/CaM complex. This suggests that a transient increase in the cytosolic concentration of free Ca2+ is not an absolute requirement for CaM-mediated activation of Src in living cells, and that a direct regulation of Src by apo-CaM could be inferred.
authors.affiliation: Department of Cancer Biology, Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/ Arturo Duperier 4, E-28029, Madrid, Spain.
authors.forename: Silviya R
authors.initials: SR
authors.lastname: Stateva
authors.affiliation: Department of Cancer Biology, Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/ Arturo Duperier 4, E-28029, Madrid, Spain; Instituto de Biología Experimental, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela.
authors.forename: Valentina
authors.initials: V
authors.lastname: Salas
authors.affiliation: Department of Cancer Biology, Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/ Arturo Duperier 4, E-28029, Madrid, Spain.
authors.forename: Estefanía
authors.initials: E
authors.lastname: Anguita
authors.affiliation: Instituto de Biología Experimental, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela; Instituto de Estudios Avanzados (IDEA), Caracas, Venezuela.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Benaim
authors.affiliation: Department of Cancer Biology, Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/ Arturo Duperier 4, E-28029, Madrid, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Villalobo
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D045744:Cell Line, Tumor; D006801:Humans; D011485:Protein Binding; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D019061:src-Family Kinases; D002118:Calcium