DOCK180, a Major CRK-Binding Protein, Alters Cell Morphology upon Translocation to the Cell Membrane

Abstract

v-Crk was identified originally as an oncogene product of the CT10 retrovirus and became the first example of an adaptor protein which consists mostly of SH2 and SH3 domains (24). The cellular homolog of v-Crk has been isolated from chickens, humans, and mice (22,33,36). Alternative splicing of the human CRK gene yields two forms of translation products, designated the 28-kDa CRK-I and 40-and 42-kDa CRK-II proteins (22). Microinjection of CRK induces neuronal differentiation of PC12 cells, and overexpression of v-Crk accelerates the neuronal differentiation of the PC12 cells induced by nerve growth factor and epidermal growth factor (EGF), which trigger the cognate tyrosine kinase receptors (13,44). This CRK-dependent differentiation requires Ras, activation of which is enhanced by overexpression of CRK (20, 44). Moreover, two guanine nucleotide exchange proteins for the Ras family protein, mSos and C3G, have been shown to bind to the SH3 domain of CRK (20). These results have assigned CRK a position between receptor-type tyrosine kinases and the Ras family proteins in the signal transduction pathway.CRK may also be involved in signalling from focal adhesions, which not only anchor cells to the extracellular matrix but also play a pivotal role in cell differentiation, migration, and proliferation (4, 16, 37). Binding of integrin to the extracellular matrix induces activation of focal adhesion tyrosine kinase bound to the cytoplasmic domain of the integrin ␤ subunit. Activated and autophosphorylated focal adhesion tyrosine kinase, in turn, phosphorylates paxillin, a protein bound to focal adhesion tyrosine kinase and vinculin (40). Tyrosine phosphorylation of p130 cas is also induced by integrin engagement (31). Because paxillin and p130 cas are two of the three major phosphotyrosine-containing proteins in Crk-transformed cells and bind to the SH2 domain of Crk (21, 26), Crk seems to have an important role in signalling from focal adhesions.The adaptor proteins, including Crk, Grb2/Ash, and Nck, perceive signals from a number of tyrosine kinases by the interaction of SH2 with phosphotyrosine-containing peptides (34). The signals are next transmitted to the proteins bound to the SH3 domains through proline-rich sequences (5, 34). By using far Western blotting, we and others have previously shown that the SH3 domain of CRK binds to 135-to 145-, 160-, and 180-kDa proteins (7,44). The 135-to 145-kDa proteinsis designated C3G and has been shown to be a guanine nucleotide exchange protein for Rap1 (45). The identities of the 160-and 180-kDa proteins have not been reported. Other proteins known to bind to the SH3 domain of Crk include Sos (7,20), Abl (8), and Eps15 (43).A function of an adaptor protein is to recruit cytoplasmic enzymes bound to its SH3 domain to the cell membrane (34). Thus, the membrane targeting of the SH3-binding proteins mimics the activation of SH3-binding proteins. A typical example is Sos, a guanine nucleotide exchange protein for Ras, which binds to the SH3 domains of Grb2. Membrane targeting of...

Stress signaling in Drosophila

“…Human DOCK180 has been implicated in regulating cell morphology when targeted to the cell membrane (Hasegawa et al, 1996). In addition, biochemical data revealed a physical interaction between DOCK180 and Crk, an adaptor protein localized to sites of cell adhesion (Hasegawa et al, 1996). Taken together, a plausible functional model consistent with the reported data is that Mbc/ DOCK180 may in¯uence Rac-mediated changes in membrane morphology or cytoskeleton through recruitment to speci®c subcellular sites or through localized activation of Rac at the membrane.…”

“…However, in cotransfection assays in vertebrate cells, the human homolog of Mbc, DOCK180, interacts exclusively with Rac in a nucleotide-independent manner (Nolan et al, 1998). Human DOCK180 has been implicated in regulating cell morphology when targeted to the cell membrane (Hasegawa et al, 1996). In addition, biochemical data revealed a physical interaction between DOCK180 and Crk, an adaptor protein localized to sites of cell adhesion (Hasegawa et al, 1996).…”

Identification of Tyr-762 in the platelet-derived growth factor α-receptor as the binding site for Crk proteins

“…The SH3 domains have been shown to bind to e.g. the cytoplasmic tyrosine kinase c-Abl, the adaptor molecule DOCK180, and the guanine nucleotide exchange factor C3G and Sos (Feller et al, 1994;Hasegawa et al, 1996;Knudsen et al, 1995;Matsuda et al, 1996;Reedquist et al, 1996;Tanaka et al, 1994).…”

Crk protein binds to PDGF receptor and insulin receptor substrate-1 with different modulating effects on PDGF- and insulin-dependent signaling pathways

“…Further, guanine-nucleotide exchange factors C3G and Sos have been described as intracellular targets of c-Crk SH3 domains Knudsen et al, 1994;Matsuda et al, 1994). Recently, protein DOCK180, that was shown to be involved in the control of cell morphology, has been described as a major target for Crk SH3 domain (Hasegawa et al, 1996). Association of Crk SH3 domain with a substrate of EGF receptor EPS15 was also reported Hansen et al, 1997).…”