Role of the Integrin-Linked Kinase, ILK, in Mammary Carcinogenesis.

摘要

Yeast two-hybrid screens for proteins interacting with the integrin linked kinase, ILK1, identified a protein phosphatase 2C, ILKAP, that blocks ILK1 activity and signaling. A second interacting protein contains two calponin homology (CH) domains, suggestive of actin-binding function. Conditional expression of ILKAP indicated that it selectively inhibited ILK1 kinase activity, and subsequent signaling through GSK3-beta and beta-catenin, components of the Wnt signal transduction pathway. This down-regulation requires ILKAP catalytic activity. A second interacting protein, Clint, contains a tendem arrangement of two calponin homology (CH) domain suggestive of actin-binding function. ILK1 binds to the C-terminal CH domain of Clint. Clint mRNA is highly preferentially expressed in human strained muscle tissues, and an apparently single protein of apparent molecular weight of 35 kDa is recognized by antibodies raised to a Clint fusion protein. Interaction of ILK1 with Clint may require the catalytic function of ILK1 since a kinase-dead version of ILK was deficient for Clint binding. As this kinase dead ILK1 acts as a dominant negative mutation, this suggests Clint interactions are important in ILK1- mediated signaling. ILK1 can phosphorylate recombinant Clint protein, indicating that Clint could be a physiologic substrate for ILK1. We characterize a regulator and a potential substrate, of ILK1.