TY - JOUR
T1 - A novel protein kinase B (PKB)/AKT-binding protein enhances PKB kinase activity and regulates DNA synthesis
AU - Anai, Motonobu
AU - Shojima, Nobuhiro
AU - Katagiri, Hideki
AU - Ogihara, Takehide
AU - Sakoda, Hideyuki
AU - Onishi, Yukiko
AU - Ono, Hiraku
AU - Fujishiro, Midori
AU - Fukushima, Yasushi
AU - Horike, Nanao
AU - Viana, Amelia
AU - Kikuchi, Masatoshi
AU - Noguchi, Noriko
AU - Takahashi, Shinichiro
AU - Takata, Kuniaki
AU - Oka, Yoshitomo
AU - Uchijima, Yasunobu
AU - Kurihara, Hiroki
AU - Asano, Tomoichiro
PY - 2005/5/6
Y1 - 2005/5/6
N2 - Protein kinase B (PKB)/Akt reportedly plays a role in the survival and/or proliferation of cells. We identified a novel protein, which binds to PKB, using a yeast two-hybrid screening system. This association was demonstrated not only in vivo by overexpressing both proteins or by coimmunoprecipitation of the endogenous proteins, but also in vitro using glutathione S-transferase fusion proteins. Importantly, this protein specifically associates with the C terminus of PKB but not with other AGC kinases and enhances PKB phosphorylation and kinase activation without growth factor stimulation. Thus, we termed this Akt-specific binding protein APE (Akt-phosphorylation enhancer). Since APE-induced phosphorylation of PKB did not occur in cells treated with wortmannin or LY294002, APE itself is not a kinase but seems to enhance or prolong the phosphoinositide 3-kinase-dependent phosphorylation of PKB. In cells in which APE was suppressed by small interfering RNA, DNA synthesis was significantly reduced with suppression of PKB phosphorylation, suggesting a synergistic role of APE in PKB-induced proliferation. On the other hand, in cells overexpressing both PKB and APE, despite markedly increased basal phosphorylation of PKB, both DNA rereplication and subsequent Chk2 phosphorylation and apoptosis were seen, suggesting the involvement of APE in the regulation of cell cycling replication licensing. Taking these observations together, APE appears to be a novel regulator of PKB phosphorylation. Furthermore, the interaction between APE and PKB, possibly dependent on the expression levels of both proteins, may be a novel molecular mechanism leading to proliferation and/or apoptosis.
AB - Protein kinase B (PKB)/Akt reportedly plays a role in the survival and/or proliferation of cells. We identified a novel protein, which binds to PKB, using a yeast two-hybrid screening system. This association was demonstrated not only in vivo by overexpressing both proteins or by coimmunoprecipitation of the endogenous proteins, but also in vitro using glutathione S-transferase fusion proteins. Importantly, this protein specifically associates with the C terminus of PKB but not with other AGC kinases and enhances PKB phosphorylation and kinase activation without growth factor stimulation. Thus, we termed this Akt-specific binding protein APE (Akt-phosphorylation enhancer). Since APE-induced phosphorylation of PKB did not occur in cells treated with wortmannin or LY294002, APE itself is not a kinase but seems to enhance or prolong the phosphoinositide 3-kinase-dependent phosphorylation of PKB. In cells in which APE was suppressed by small interfering RNA, DNA synthesis was significantly reduced with suppression of PKB phosphorylation, suggesting a synergistic role of APE in PKB-induced proliferation. On the other hand, in cells overexpressing both PKB and APE, despite markedly increased basal phosphorylation of PKB, both DNA rereplication and subsequent Chk2 phosphorylation and apoptosis were seen, suggesting the involvement of APE in the regulation of cell cycling replication licensing. Taking these observations together, APE appears to be a novel regulator of PKB phosphorylation. Furthermore, the interaction between APE and PKB, possibly dependent on the expression levels of both proteins, may be a novel molecular mechanism leading to proliferation and/or apoptosis.
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U2 - 10.1074/jbc.M500586200
DO - 10.1074/jbc.M500586200
M3 - Article
C2 - 15753085
AN - SCOPUS:24044521010
VL - 280
SP - 18525
EP - 18535
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 18
ER -