Cofilin phosphorylation by protein kinase testicular protein kinase 1 and its role in integrin-mediated actin reorganization and focal adhesion formation.
Testicular protein kinase 1 (TESK1) is a serine/threonine kinase with a structure composed of a kinase domain related to those of LIM-kinases and a unique C-terminal proline-rich domain. Like LIM-kinases, TESK1 phosphorylated cofilin specifically at Ser-3, both in vitro and in vivo. When expressed in HeLa cells, TESK1 stimulated the formation of actin stress fibers and focal adhesions. In contrast to LIM-kinases, the kinase activity of TESK1 was not enhanced by Rho-associated kinase (ROCK) or p21-activated kinase, indicating that TESK1 is not their downstream effector. Both the kinase activity of TESK1 and the level of cofilin phosphorylation increased by plating cells on fibronectin. Y-27632, a specific inhibitor of ROCK, inhibited LIM-kinase-induced cofilin phosphorylation but did not affect fibronectin-induced or TESK1-induced cofilin phosphorylation in HeLa cells. Expression of a kinase-negative TESK1 suppressed cofilin phosphorylation and formation of stress fibers and focal adhesions induced in cells plated on fibronectin. These results suggest that TESK1 functions downstream of integrins and plays a key role in integrin-mediated actin reorganization, presumably through phosphorylating and inactivating cofilin. We propose that TESK1 and LIM-kinases commonly phosphorylate cofilin but are regulated in different ways and play distinct roles in actin reorganization in living cells.
Toshima
J
J
Biological Institute, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
Toshima
J Y
JY
Amano
T
T
Yang
N
N
Narumiya
S
S
Mizuno
K
K
D051339:Actin Depolymerizing Factors; D000199:Actins / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D051345:Destrin; D022001:Focal Adhesions / Q000378:metabolism* / Q000502:physiology; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D008840:Microfilament Proteins / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*; D054462:p21-Activated Kinases; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D054460:rho-Associated Kinases
D051339:Actin Depolymerizing Factors; D000199:Actins; D051345:Destrin; D016023:Integrins; D047908:Intracellular Signaling Peptides and Proteins; D008840:Microfilament Proteins; C097507:testis-specific protein kinase 1; C515903:PAK1 protein, human; C515906:Pak1 protein, rat; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D054460:rho-Associated Kinases; D020741:rho GTP-Binding Proteins