Protein kinase CK2 phosphorylates and activates p21-activated kinase 1

Abstract

P21-activated kinase 1 (PAK1) activation is achieved through relief of autoinhibition. The authors show that this event is not sufficient to bring about PAK1 activation but is required for CK2-dependent PAK1S223 phosphorylation, which enables PAK1 to be catalytically competent. S223 phosphorylation is crucial for PAK1 GTPase-dependent and GTPase-independent activation.

The Role of the Pleckstrin Homology Domain-containing Protein CKIP-1 in Activation of p21-activated Kinase 1 (PAK1)

“…Our results have demonstrated that CK2 phosphorylation of Ser-223 is crucial for activation of PAK1 (26), and that this process is regulated by PI3K (this study). The kinase activity of a constitutively active PAK1 (PAK1 H83,86L ), postulated to mimicGTPase-inducedstructuralchanges(47),requiresphosphorylation of Ser-223, suggesting that Ser-223 may become available for phosphorylation by CK2 after the conformational change (26). Therefore, PI3K-dependent, CKIP-1-mediated recruitment of CK2␣ to the plasma membrane is essentially required for the activation of PAK1.…”

“…We have recently demonstrated that CK2 catalyzes phosphorylation of PAK1 at Ser-223, which is critical for the activation of the kinase (26). Here, we show evidence that CKIP-1 appears to recruit CK2␣ to PAK1 in response to EGF in a PI3K-dependent manner.…”

“…phosphorylates Ser-223 of PAK1, and that a phosphomimetic mutation at Ser-223 (Ser to Glu) generates a constitutively active PAK1 (26). We find that, upon EGF treatment, PAK1 is recruited to the plasma membrane (Fig.…”

“…The protein samples were resolved on a 10% SDS-PAGE gel and transferred to a nitrocellulose membrane. Antibodies used in this study include anti-phospho-PAK1 S223 (26), anti-phospho-PAK1 S144 , anti-PAK1, anti-Na/K-ATPase (Cell Signaling), anti-CK2␣, anti-GFP (Santa Cruz Biotechnology), anti-␣-tubulin (Neo Markers), anti-phospho-p41-Arc T21 (ECM Biosciences), and anti-CKIP-1 (Sigma-Aldrich) antibodies.…”

“…Thus, these observations indicate that PI3K is required for PAK1-mediated cell migration. (26). Given that CKIP-1 regulates PAK1 activity (Figs.…”