Vinexin beta regulates the anchorage dependence of ERK2 activation stimulated by epidermal growth factor.
ERK is activated by soluble growth factors in adherent cells. However, activation of ERK is barely detectable and not sufficient for cell proliferation in non-adherent cells. Here, we show that exogenous expression of vinexin beta, a novel focal adhesion protein, allows anchorage-independent ERK2 activation stimulated by epidermal growth factor. In contrast, expression of vinexin beta had no effect on ERK2 activation in adherent cells, suggesting that vinexin beta regulates the anchorage dependence of ERK2 activation. Analyses using deletion mutants demonstrated that a linker region between the second and third SH3 domains of vinexin beta, but not the SH3 domains, is required for this function of vinexin beta. To evaluate the pathway regulating the anchorage dependence of ERK2 activation, we used a dominant-negative mutant of p21-activated kinase (PAK) and a specific inhibitor (H89) of cAMP-dependent protein kinase (PKA) because PAK and PKA are known to regulate the anchorage dependence of ERK2 activation. The dominant-negative mutant of PAK suppressed the anchorage-independent ERK2 activation induced by expression of vinexin beta. The dominant-negative mutant of vinexin beta inhibited the anchorage-independent ERK2 activation induced by the PKA inhibitor. Together, these observations indicate that vinexin beta plays a key role in regulating the anchorage dependence of ERK2 activation through PKA-PAK signaling.
Suwa
Akira
A
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Mitsushima
Masaru
M
Ito
Takuya
T
Akamatsu
Masahiko
M
Ueda
Kazumitsu
K
Amachi
Teruo
T
Kioka
Noriyuki
N
D016475:3T3 Cells; D000818:Animals; D002448:Cell Adhesion; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000502:physiology*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D009124:Muscle Proteins / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction; D018909:src Homology Domains; D048868:Adaptor Proteins, Signal Transducing
D017868:Cyclic AMP-Dependent Protein Kinases; D004815:Epidermal Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D009124:Muscle Proteins; D017346:Protein Serine-Threonine Kinases; C117452:Sorbs3 protein, mouse; D048868:Adaptor Proteins, Signal Transducing