title: Activation of protein kinase D3 by signaling through Rac and the alpha subunits of the heterotrimeric G proteins G12 and G13.
abstract: PKD is the founding member of a novel protein kinase family that also includes PKD2 and PKD3. PKD has been the focus of most studies up to date, but little is known about the mechanisms that mediate PKD3 activation. Here, we show that addition of aluminum fluoride to COS-7 cells cotransfected with PKD3 and Galpha13 or Galpha12 induced PKD3 activation, which was associated with a transient plasma membrane translocation of cytosolic PKD3. Treatment with Clostridium difficile toxin B blocked PKD3 activation induced by either bombesin or by aluminum fluoride-stimulated Galpha12/13 but did not affect Galphaq-induced PKD3 activation. Furthermore, PKD3 immunoprecipitated from cells cotransfected with a constitutively active Rac (RacV12) exhibited a marked increase in PKD3 basal catalytic activity. In contrast, cotransfection with active Rho (RhoQ63L), Cdc42 (Cdc42Q61L), or Ras (RasV12) did not promote PKD3 activation. Expression of either COOH-terminal dominant-negative fragment of Galpha13 or dominant negative Rac (Rac N17) attenuated bombesin-induced PKD3 activation. Treatment with protein kinase C (PKC) inhibitors prevented the increase in PKD3 activity induced by RacV12 and aluminum fluoride-stimulated Galpha12/13. The catalytic activation of PKD3 in response to RacV12, alpha12/13 signaling or bombesin correlated with Ser-731/Ser-735 phosphorylation in the activation loop of this enzyme. Our results indicate that Galpha12/13 and Rac are important components in the signal transduction pathways that mediate bombesin receptor-induced PKD3 activation.
authors.affiliation: Department of Medicine, David Geffen School of Medicine and Molecular Biology Institute, University of California, 900 Veteran Ave., Warren Hall, Rm. 11-124, Los Angeles, CA 90095-1786, USA.
authors.forename: Jingzhen
authors.initials: J
authors.lastname: Yuan
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Rey
authors.forename: Enrique
authors.initials: E
authors.lastname: Rozengurt
mesh_terms: D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology; D001427:Bacterial Toxins / Q000494:pharmacology; D001839:Bombesin / Q000494:pharmacology; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D005459:Fluorides / Q000494:pharmacology; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D021381:Protein Transport; D018004:Receptors, Bombesin / Q000819:agonists; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D017607:Aluminum Compounds; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D018004:Receptors, Bombesin; C031815:toxB protein, Clostridium difficile; D012694:Serine; C119190:protein kinase C nu; D011493:Protein Kinase C; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D018631:ras Proteins; D020741:rho GTP-Binding Proteins; D001839:Bombesin; D005459:Fluorides; C032311:aluminum fluoride