Type II p21-activated kinases (PAKs) are regulated by an autoinhibitory pseudosubstrate.

The type II p21-activated kinases (PAKs) are key effectors of RHO-family GTPases involved in cell motility, survival, and proliferation. Using a structure-guided approach, we discovered that type II PAKs are regulated by an N-terminal autoinhibitory pseudosubstrate motif centered on a critical proline residue, and that this regulation occurs independently of activation loop phosphorylation. We determined six X-ray crystal structures of either full-length PAK4 or its catalytic domain, that demonstrate the molecular basis for pseudosubstrate binding to the active state with phosphorylated activation loop. We show that full-length PAK4 is constitutively autoinhibited, but mutation of the pseudosubstrate releases this inhibition and causes increased phosphorylation of the apoptotic regulation protein Bcl-2/Bcl-X(L) antagonist causing cell death and cellular morphological changes. We also find that PAK6 is regulated by the pseudosubstrate region, indicating a common type II PAK autoregulatory mechanism. Finally, we find Src SH3, but not β-PIX SH3, can activate PAK4. We provide a unique understanding for type II PAK regulation.

Citation

Byung Hak Ha, Matthew J Davis, Catherine Chen, Hua Jane Lou, Jia Gao, Rong Zhang, Michael Krauthammer, Ruth Halaban, Joseph Schlessinger, Benjamin E Turk, Titus J Boggon. Type II p21-activated kinases (PAKs) are regulated by an autoinhibitory pseudosubstrate. Proceedings of the National Academy of Sciences of the United States of America. 2012 Oct 02;109(40):16107-12

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PMID: 22988085

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