2lko | pdb_00002lko
Structural Basis of Phosphoinositide Binding to Kindlin-2 Pleckstrin Homology Domain in Regulating Integrin Activation
Structural highlights
FunctionFERM2_HUMAN Scaffolding protein that enhances integrin activation mediated by TLN1 and/or TLN2, but activates integrins only weakly by itself. Binds to membranes enriched in phosphoinositides. Enhances integrin-mediated cell adhesion onto the extracellular matrix and cell spreading; this requires both its ability to interact with integrins and with phospholipid membranes. Required for the assembly of focal adhesions. Participates in the connection between extracellular matrix adhesion sites and the actin cytoskeleton and also in the orchestration of actin assembly and cell shape modulation. Recruits FBLIM1 to focal adhesions. Plays a role in the TGFB1 and integrin signaling pathways. Stabilizes active CTNNB1 and plays a role in the regulation of transcription mediated by CTNNB1 and TCF7L2/TCF4 and in Wnt signaling.[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedKindlins are a subclass of FERM-containing proteins that have recently emerged as key regulators of integrin receptor activation and signaling. As compared with the conventional FERM domain, the kindlin FERM domain contains an inserted pleckstrin homology (PH) domain that recognizes membrane phosphoinositides, including phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-trisphosphate (PIP3). Using NMR spectroscopy, we show that PIP3 site-specifically binds to kindlin-2 PH with substantial chemical shift changes that are much larger than PIP2. This suggests an enhanced association of kindlin-2 with membrane as mediated by PIP3 upon its conversion from PIP2 by phosphoinositide-3 kinase, a known regulator of integrin activation. We determined the NMR structure of the kindlin-2 PH domain bound to the head group of PIP3, inositol 1,3,4,5-tetraphosphate (IP4). The structure reveals a canonical PH domain fold, yet with a distinct IP4 binding pocket that appears highly conserved for the kindlin family members. Functional experiments demonstrate that although wild type kindlin-2 is capable of cooperating with integrin activator talin to induce synergistic integrin alpha(IIb)beta(3) activation, this ability is significantly impaired for a phosphoinositide binding-defective kindlin-2 mutant. These results define a specific PIP3 recognition mode for the kindlin PH domain. Moreover, they shed light upon a mechanism as to how the PH domain mediates membrane engagement of kindlin-2 to promote its binding to integrin and cooperation with talin for regulation of integrin activation. Structural basis of phosphoinositide binding to kindlin-2 protein pleckstrin homology domain in regulating integrin activation.,Liu J, Fukuda K, Xu Z, Ma YQ, Hirbawi J, Mao X, Wu C, Plow EF, Qin J J Biol Chem. 2011 Dec 16;286(50):43334-42. Epub 2011 Oct 26. PMID:22030399[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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