title: Integrin-linked kinase is localized to cell-matrix focal adhesions but not cell-cell adhesion sites and the focal adhesion localization of integrin-linked kinase is regulated by the PINCH-binding ANK repeats.
abstract: Integrin-linked kinase (ILK) is a ubiquitously expressed protein serine/threonine kinase that has been implicated in integrin-, growth factor- and Wnt-signaling pathways. In this study, we show that ILK is a constituent of cell-matrix focal adhesions. ILK was recruited to focal adhesions in all types of cells examined upon adhesion to a variety of extracellular matrix proteins. By contrast, ILK was absent in E-cadherin-mediated cell-cell adherens junctions. In previous studies, we have identified PINCH, a protein consisting of five LIM domains, as an ILK binding protein. We demonstrate in this study that the ILK-PINCH interaction requires the N-terminal-most ANK repeat (ANK1) of ILK and one (the C-terminal) of the two zinc-binding modules within the LIM1 domain of PINCH. The ILK ANK repeats domain, which is capable of interacting with PINCH in vitro, could also form a complex with PINCH in vivo. However, the efficiency of the complex formation or the stability of the complex was markedly reduced in the absence of the C-terminal domain of ILK. The PINCH binding defective ANK1 deletion ILK mutant, unlike the wild-type ILK, was unable to localize and cluster in focal adhesions, suggesting that the interaction with PINCH is necessary for focal adhesion localization and clustering of ILK. The N-terminal ANK repeats domain, however, is not sufficient for mediating focal adhesion localization of ILK, as an ILK mutant containing the ANK repeats domain but lacking the C-terminal integrin binding site failed to localize in focal adhesions. These results suggest that focal adhesions are a major subcellular compartment where ILK functions in intracellular signal transduction, and provide important evidence for a critical role of PINCH and integrins in regulating ILK cellular function.
authors.affiliation: Department of Cell Biology and The Cell Adhesion and Matrix Research Center, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA.
authors.forename: F
authors.initials: F
authors.lastname: Li
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: C
authors.initials: C
authors.lastname: Wu
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017487:Ankyrins; D002448:Cell Adhesion; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000201:enzymology; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D060588:LIM Domain Proteins; D008565:Membrane Proteins; D051379:Mice; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D000099200:Scaffold Protein ILK
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D017487:Ankyrins; D004268:DNA-Binding Proteins; D016326:Extracellular Matrix Proteins; D060588:LIM Domain Proteins; D008565:Membrane Proteins; D017346:Protein Serine-Threonine Kinases; D000099200:Scaffold Protein ILK; C490232:Lims1 protein, mouse