| Structural highlights
Function
PAK4_HUMAN Serine/threonine protein kinase that plays a role in a variety of different signaling pathways including cytoskeleton regulation, cell migration, growth, proliferation or cell survival. Activation by various effectors including growth factor receptors or active CDC42 and RAC1 results in a conformational change and a subsequent autophosphorylation on several serine and/or threonine residues. Phosphorylates and inactivates the protein phosphatase SSH1, leading to increased inhibitory phosphorylation of the actin binding/depolymerizing factor cofilin. Decreased cofilin activity may lead to stabilization of actin filaments. Phosphorylates LIMK1, a kinase that also inhibits the activity of cofilin. Phosphorylates integrin beta5/ITGB5 and thus regulates cell motility. Phosphorylates ARHGEF2 and activates the downstream target RHOA that plays a role in the regulation of assembly of focal adhesions and actin stress fibers. Stimulates cell survival by phosphorylating the BCL2 antagonist of cell death BAD. Alternatively, inhibits apoptosis by preventing caspase-8 binding to death domain receptors in a kinase independent manner. Plays a role in cell-cycle progression by controlling levels of the cell-cycle regulatory protein CDKN1A and by phosphorylating RAN.[1] [2] [3] [4] [5] [6] [7]
Publication Abstract from PubMed
Six human PAK members are classified into groups I (PAKs 1-3) and II (PAK4-6). Previously, only group I PAKs were thought to be auto-inhibited but very recently PAK4, the prototype of group II PAKs, has also been shown to be auto-inhibited by its N-terminal regulatory domain. However, the complete auto-inhibitory domain (AID) sequence remains undefined and the mechanism underlying its auto-inhibition is largely elusive. Here, the N-terminal regulatory domain of PAK4 sufficient for auto-inhibiting and binding Cdc42/Rac was characterized to be intrinsically unstructured, but nevertheless we identified the entire AID sequence by NMR. Strikingly, an AID peptide was derived by deleting the binding-unnecessary residues, which has a Kd of 320nM to the PAK4 catalytic domain. Consequently, the PAK4 crystal structure complexed with the entire AID has been determined, which reveals that the complete kinase cleft is occupied by 20 AID residuescomposed of an N-terminal alpha-helix and a previously-identified pseudosubstrate motif, thus achieving auto-inhibition. Our study reveals that PAK4 is auto-inhibited by a novel mechanism which is completely different from that for PAK1, thus bearing critical implications for design of inhibitors specific for group II PAKs.
NMR binding and crystal structure reveal that intrinsically-unstructured regulatory domain auto-inhibits PAK4 by a mechanism different from that of PAK1.,Wang W, Lim L, Baskaran Y, Manser E, Song J Biochem Biophys Res Commun. 2013 Jul 20. pii: S0006-291X(13)01198-4. doi:, 10.1016/j.bbrc.2013.07.047. PMID:23876315[8]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Gnesutta N, Qu J, Minden A. The serine/threonine kinase PAK4 prevents caspase activation and protects cells from apoptosis. J Biol Chem. 2001 Apr 27;276(17):14414-9. Epub 2001 Jan 24. PMID:11278822 doi:10.1074/jbc.M011046200
- ↑ Qu J, Cammarano MS, Shi Q, Ha KC, de Lanerolle P, Minden A. Activated PAK4 regulates cell adhesion and anchorage-independent growth. Mol Cell Biol. 2001 May;21(10):3523-33. PMID:11313478 doi:10.1128/MCB.21.10.3523-3533.2001
- ↑ Gnesutta N, Minden A. Death receptor-induced activation of initiator caspase 8 is antagonized by serine/threonine kinase PAK4. Mol Cell Biol. 2003 Nov;23(21):7838-48. PMID:14560027
- ↑ Soosairajah J, Maiti S, Wiggan O, Sarmiere P, Moussi N, Sarcevic B, Sampath R, Bamburg JR, Bernard O. Interplay between components of a novel LIM kinase-slingshot phosphatase complex regulates cofilin. EMBO J. 2005 Feb 9;24(3):473-86. Epub 2005 Jan 20. PMID:15660133 doi:7600543
- ↑ Li Z, Zhang H, Lundin L, Thullberg M, Liu Y, Wang Y, Claesson-Welsh L, Stromblad S. p21-activated kinase 4 phosphorylation of integrin beta5 Ser-759 and Ser-762 regulates cell migration. J Biol Chem. 2010 Jul 30;285(31):23699-710. doi: 10.1074/jbc.M110.123497. Epub, 2010 May 27. PMID:20507994 doi:10.1074/jbc.M110.123497
- ↑ Bompard G, Rabeharivelo G, Frank M, Cau J, Delsert C, Morin N. Subgroup II PAK-mediated phosphorylation regulates Ran activity during mitosis. J Cell Biol. 2010 Sep 6;190(5):807-22. doi: 10.1083/jcb.200912056. Epub 2010 Aug , 30. PMID:20805321 doi:10.1083/jcb.200912056
- ↑ Wallace SW, Durgan J, Jin D, Hall A. Cdc42 regulates apical junction formation in human bronchial epithelial cells through PAK4 and Par6B. Mol Biol Cell. 2010 Sep 1;21(17):2996-3006. doi: 10.1091/mbc.E10-05-0429. Epub, 2010 Jul 14. PMID:20631255 doi:10.1091/mbc.E10-05-0429
- ↑ Wang W, Lim L, Baskaran Y, Manser E, Song J. NMR binding and crystal structure reveal that intrinsically-unstructured regulatory domain auto-inhibits PAK4 by a mechanism different from that of PAK1. Biochem Biophys Res Commun. 2013 Jul 20. pii: S0006-291X(13)01198-4. doi:, 10.1016/j.bbrc.2013.07.047. PMID:23876315 doi:10.1016/j.bbrc.2013.07.047
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