title: Protein kinase C delta induces Src kinase activity via activation of the protein tyrosine phosphatase PTP alpha.
abstract: Previously we have shown that protein kinase C (PKC)-mediated reorganization of the actin cytoskeleton in smooth muscle cells is transmitted by the non-receptor tyrosine kinase, Src. Several authors have described how 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulation of cells results in an increase of Src activity, but the mechanism of the PKC-mediated Src activation is unknown. Using PKC isozymes purified from Spodoptera frugiperda insect cells, we show here that PKC is not able to activate Src directly. Our data reveal that the PKC-dependent Src activation occurs via the activation of the protein tyrosine phosphatase (PTP) PTP alpha. PTP alpha becomes activated in vivo after TPA stimulation. Further, we show that PKC delta phosphorylates and activates only PTP alpha in vitro but not any other of the TPA-responsive PKC isozymes that are expressed in A7r5 rat aortic smooth muscle cells. To further substantiate our data, we show that cells lacking PKC delta have a markedly reduced PTP alpha and Src activity after 12-O-tetradecanoylphorbol-13-acetate stimulation. These data support a model in which the main mechanism of 12-O-tetradecanoylphorbol-13-acetate-induced Src activation is the direct phosphorylation and activation of PTP alpha by PKC delta, which in turn dephosphorylates and activates Src.
authors.affiliation: Medizinische Hochschule Hannover, Department of Nephrology, 30625 Hannover, Germany.
authors.forename: Dominique T
authors.initials: DT
authors.lastname: Brandt
authors.forename: Axel
authors.initials: A
authors.lastname: Goerke
authors.forename: Marion
authors.initials: M
authors.lastname: Heuer
authors.forename: Mario
authors.initials: M
authors.lastname: Gimona
authors.forename: Michael
authors.initials: M
authors.lastname: Leitges
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kremmer
authors.forename: Reiner
authors.initials: R
authors.lastname: Lammers
authors.forename: Hermann
authors.initials: H
authors.lastname: Haller
authors.forename: Harald
authors.initials: H
authors.lastname: Mischak
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001011:Aorta / Q000166:cytology; D002273:Carcinogens; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D007313:Insecta; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000166:cytology; D009130:Muscle, Smooth / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D051745:Protein Kinase C-delta; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D000199:Actins; D002273:Carcinogens; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; C497259:Prkcd protein, mouse; C497260:Prkcd protein, rat; D019061:src-Family Kinases; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D017027:Protein Tyrosine Phosphatases; D013755:Tetradecanoylphorbol Acetate