Initiation of cofilin activity in response to EGF is uncoupled from cofilin phosphorylation and dephosphorylation in carcinoma cells.
It has been demonstrated that the actin-severing activity of cofilin can be downregulated by LIM kinase (LIMK)-dependent phosphorylation at residue Ser3. Chemotactic stimulation in various cell types induces cofilin dephosphorylation, suggesting that cofilin activation in these cells occurs by a dephosphorylation mechanism. However, resting metastatic carcinoma cells have the majority of their cofilin in a dephosphorylated but largely inactive state. Stimulation with epidermal growth factor (EGF) induces an increase in cofilin activity after 60 seconds together with an increase in phosphorylated cofilin (p-cofilin), indicating that cofilin dephosphorylation is not coupled to cofilin activation in these cells. Suppression of LIMK function by inhibiting Rho-associated protein kinase (ROCK) or LIMK siRNA inhibited the EGF-induced cofilin phosphorylation but had no effect on cofilin activity or cofilin-dependent lamellipod protrusion induced by EGF. Correlation analysis revealed that cofilin, p-cofilin and LIMK are not colocalized, and changes in the location of these proteins upon stimulation with EGF indicate that they are not functionally coupled. Phospholipase C, which has been implicated in cofilin activation following stimulation with EGF, does not regulate p-cofilin levels following stimulation with EGF. Therefore, our results do not support a model for the initial activation of cofilin by dephosphorylation in response to chemoattractant stimulation in metastatic carcinoma cells.
Song
Xiaoyan
X
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine of Yeshiva University, F628, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA.
Chen
Xiaoming
X
Yamaguchi
Hideki
H
Mouneimne
Ghassan
G
Condeelis
John S
JS
Eddy
Robert J
RJ
D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000818:Animals; D003599:Cytoskeleton / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D054461:Lim Kinases; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology; D017830:Octoxynol / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D011554:Pseudopodia / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism; D054460:rho-Associated Kinases
D051339:Actin Depolymerizing Factors; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D004815:Epidermal Growth Factor; D017830:Octoxynol; D011494:Protein Kinases; D054461:Lim Kinases; C515894:Limk1 protein, rat; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D010738:Type C Phospholipases