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Cytoplasmic localization of p21Cip1/WAF1 by Akt-induced phosphorylation in HER-2/neu-overexpressing cells


Amplification or overexpression of HER-2/neu in cancer cells confers resistance to apoptosis and promotes cell growth. The cellular localization of p21Cip1/WAF1 has been proposed to be critical either in promoting cell survival or in inhibiting cell growth. Here we show that HER-2/neu-mediated cell growth requires the activation of Akt, which associates with p21Cip1/WAF1 and phosphorylates it at threonine 145, resulting in cytoplasmic localization of p21Cip1/WAF1. Furthermore, blocking the Akt pathway with a dominant-negative Akt mutant restores the nuclear localization and cell-growth-inhibiting activity of p21Cip1/WAF1. Our results indicate that HER-2/neu induces cytoplasmic localization of p21Cip1/WAF1 through activation of Akt to promote cell growth, which may have implications for the oncogenic activity of HER-2/neu and Akt.

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Figure 1: The Akt pathway is required for HER-2/neu-mediated cell proliferation.
Figure 2: Threonine 145 of p21Cip1/WAF1 is phosphorylated in vivo.
Figure 3: Akt interacts with p21Cip1/WAF1 and phosphorylates it at threonine 145.
Figure 4: Akt alters the cellular localization of p21Cip1/WAF1.
Figure 5: Cellular localization of endogenous p21Cip1/WAF1.
Figure 6: HER-2/neu activates Akt and induces cytoplasmic localization of p21Cip1/WAF1 in breast tumours.
Figure 7: Growth-inhibiting activities of p21Cip1/WAF1 mutants.
Figure 8: Model for HER-2/neu-induced cytoplasmic localization of p21Cip1/WAF1 through activation of Akt.


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We thank D. Yu, R. B. Arlinghaus and W. H. Klein for critical comments on the manuscript. This work was supported by grants from the National Institutes of Health (to M-C.H.), by a SPORE grant in ovarian cancer (to M-C.H.), and by the Nellie Connally Breast Cancer Research Fund at the M. D. Anderson Cancer Center (M-C.H.). B.P.Z. is a recipient of a postdoctoral fellowship from the US Department of Defense Breast Cancer Research.

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Correspondence to Mien-Chie Hung.

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Zhou, B., Liao, Y., Xia, W. et al. Cytoplasmic localization of p21Cip1/WAF1 by Akt-induced phosphorylation in HER-2/neu-overexpressing cells. Nat Cell Biol 3, 245–252 (2001).

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