Protein kinase D regulates RhoA activity via rhotekin phosphorylation.
The members of the protein kinase D (PKD) family of serine/threonine kinases are major targets for tumor-promoting phorbol esters, G protein-coupled receptors, and activated protein kinase C isoforms (PKCs). The expanding list of cellular processes in which PKDs exert their function via phosphorylation of various substrates include proliferation, apoptosis, migration, angiogenesis, and vesicle trafficking. Therefore, identification of novel PKD substrates is necessary to understand the profound role of this kinase family in signal transduction. Here, we show that rhotekin, an effector of RhoA GTPase, is a novel substrate of PKD. We identified Ser-435 in rhotekin as the potential site targeted by PKD in vivo. Expression of a phosphomimetic S435E rhotekin mutant resulted in an increase of endogenous active RhoA GTPase levels. Phosphorylation of rhotekin by PKD2 modulates the anchoring of the RhoA in the plasma membrane. Consequently, the S435E rhotekin mutant displayed enhanced stress fiber formation when expressed in serum-starved fibroblasts. Our data thus identify a novel role of PKD as a regulator of RhoA activity and actin stress fiber formation through phosphorylation of rhotekin.
Department of Internal Medicine I, University of Ulm, Ulm, Germany.
Ganesh V
GV
Pusapati
Tim
T
Eiseler
An
A
Rykx
Sandy
S
Vandoninck
Rita
R
Derua
Etienne
E
Waelkens
Johan
J
Van Lint
Götz
G
von Wichert
Thomas
T
Seufferlein
D020816:Amino Acid Motifs; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D019204:GTP-Binding Proteins; D057809:HEK293 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; D047908:Intracellular Signaling Peptides and Proteins; C100494:RTKN protein, human; C089212:protein kinase D; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein