A Molecular Mechanism for the Requirement of PAT-4 (Integrin-linked Kinase (ILK)) for the Localization of UNC-112 (Kindlin) to Integrin Adhesion Sites

• Published in: The Journal of biological chemistry Vol. 287; no. 34; pp. 28537 - 28551
• Main Authors: Qadota, Hiroshi, Moerman, Donald G., Benian, Guy M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 17.08.2012; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Substitution; Animals; C. elegans; Caenorhabditis elegans - genetics; Caenorhabditis elegans - metabolism; Caenorhabditis elegans Proteins - genetics; Caenorhabditis elegans Proteins - metabolism; Cell Adhesion Molecules - genetics; Cell Adhesion Molecules - metabolism; Cell Biology; ILK; Integrin; Kindlin; Models, Biological; Muscle; Mutation, Missense; Protein Binding - physiology; Protein Serine-Threonine Kinases - genetics; Protein Serine-Threonine Kinases - metabolism; Protein Structure, Tertiary; Protein Transport - physiology; Protein-Protein Interactions; Signal Transduction; Kindlin; C. elegans; Integrin; Signal Transduction; ILK; Muscle; Protein-Protein Interactions
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.354852

Caenorhabditis elegans muscle cells attach to basement membrane through adhesion plaques. PAT-3 (β-integrin), UNC-112 (kindlin), and PAT-4 (integrin-linked kinase) are associated with these structures. Genetic analysis indicated that PAT-4 is required for UNC-112 to be properly localized. We investigated the molecular basis of this requirement. We show that the cytoplasmic tail of PAT-3 binds to full-length UNC-112 and that the N- and C-terminal halves of UNC-112 bind to each other. We demonstrate competition between the UNC-112 C-terminal half and PAT-4 for binding to the UNC-112 N-terminal half. The D382V mutation results in lack of binding to PAT-4 and lack of localization to adhesion structures. T346A or E349K mutations, which abolish interaction of the N- and C-terminal halves, permit D382V UNC-112 to localize to adhesion structures. The following model is proposed. UNC-112 exists in closed inactive and open active conformations, and upon binding of PAT-4 to the UNC-112 N-terminal half, UNC-112 is converted into the open state, able to bind to PAT-3. Background: PAT-4 (ILK) is required for localization of UNC-112 (kindlin) to integrin adhesion sites. Results: N- and C-terminal halves of UNC-112 interact, and mutations abolishing this interaction restore the ability of a mutant UNC-112 that cannot bind PAT-4 to localize. Conclusion: UNC-112 exists in two conformations, and binding to PAT-4 converts UNC-112 to an open state. Significance: This molecular mechanism may be conserved among kindlins.