Involvement of phosphatases in the anchorage-dependent regulation of ERK2 activation.
Activation of extracellular signal-regulated kinase (ERK) is known to be regulated by cell adhesion, namely "anchorage dependence". Most studies on the anchorage-dependent regulation have focused on the upstream activating components. We previously reported that the focal adhesion protein vinexin beta can induce the anchorage-independent activation of ERK2. We show here that vinexin beta-induced anchorage-independent activation of ERK2 involves prevention of the dephosphorylation of ERK2, but not the promotion of MEK1 or Raf1 activity. Furthermore, knockdown of vinexin beta resulted in a faster dephosphorylation of ERK2 in A549 cells. Moreover, the coexpression of MKP3/rVH6, an ERK2 specific phosphatase, suppressed the anchorage-independent activation of ERK2 induced by vinexin beta. These results suggest that vinexin beta can prevent the dephosphorylation of ERK2 stimulated by cell detachment, leading to the anchorage-independent activation of ERK2. Furthermore, we found that phosphatase activity directed against activated ERK2 was higher in suspended cells than in adherent cells. In addition, orthovanadate efficiently induces anchorage-independent activation of ERK2 without marked activation of MEK1 in NIH3T3 cells. These observations suggest that the anchorage dependence of ERK1/2 activation is regulated not only by upstream kinases, Raf1 and MEK, but also by phosphatases acting against ERK1/2 and that vinexin beta can induce anchorage-independent activation of ERK by preventing the inactivation of ERK1/2.
Mitsushima
Masaru
M
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Ueda
Kazumitsu
K
Kioka
Noriyuki
N
D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D054642:Dual Specificity Phosphatase 6; D004789:Enzyme Activation / Q000502:physiology; D022001:Focal Adhesions / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology; D048868:Adaptor Proteins, Signal Transducing
D054642:Dual Specificity Phosphatase 6; D017261:Glycosylphosphatidylinositols; D048369:MAP Kinase Kinase 1; D019950:Mitogen-Activated Protein Kinase 1; D009124:Muscle Proteins; D010749:Phosphoprotein Phosphatases; D017027:Protein Tyrosine Phosphatases; D019908:Proto-Oncogene Proteins c-raf; D014638:Vanadates; C117452:Sorbs3 protein, mouse; D048868:Adaptor Proteins, Signal Transducing; C482127:Map2k1 protein, mouse; C517035:DUSP6 protein, human; C517036:Dusp6 protein, mouse