Nck-2, a novel Src homology2/3-containing adaptor protein that interacts with the LIM-only protein PINCH and components of growth factor receptor kinase-signaling pathways

Many of the protein-protein interactions that are essential for eukaryotic intracellular signal transduction are mediated by protein binding modules i ncluding SH2, SH3, and LIM domains. Nck is a SH3- and SH2-containing adapto r protein implicated in coordinating various signaling pathways, including those of growth factor receptors and cell adhesion receptors. We report her e the identification, cloning, and characterization of a widely expressed, Nck-related adaptor protein termed Nck-2. Nck-2 comprises primarily three N -terminal SH3 domains and one C-terminal SH2 domain. We show that Nck-2 int eracts with PINCH, a LIM-only protein implicated in integrin-linked kinase signaling. The PINCH-Nck-2 interaction is mediated by the fourth LIM domain of PINCH and the third SH3 domain of Nck-2. Furthermore, we show that Nck- 2 is capable of recognizing several key components of growth factor recepto r kinase-signaling pathways including EGF receptors, PDGF receptor-beta, an d IRS-1. The association of Nck-2 with EGF receptors was regulated by EGF s timulation aid involved largely the SH2 domain of Nck-2, although the SH3 d omains of Nck-2 also contributed to the complex formation. The association of Nck-2 with PDGF receptor-P was dependent on PDGF activation and was medi ated solely by the SH2 domain of Nck-2. Additionally, we have detected a st able association between Nck-2 and IRS-1 that was mediated primarily via th e second and third SH3 domain of Nck-2. Thus, Nck-2 associates with PINCH a nd components of different growth factor receptor-signaling pathways via di stinct mechanisms. Finally, we provide evidence indicating that a fraction of the Nck-2 and/or Nck-1 proteins are associated with the cytoskeleton. Th ese results identify a novel Nck-related SH2- and SH3-domain-containing pro tein and suggest that it may function as an adaptor protein connecting the growth factor receptor-signaling pathways with the integrin-signaling pathw ays.