title: Membrane recruitment of DOCK180 by binding to PtdIns(3,4,5)P3.
abstract: DOCK180 was originally identified as one of two major proteins bound to the Crk oncogene product and became an archetype of the CDM family of proteins, including Ced-5 of Caenorhabditis elegans and Mbc of Drosophila melanogaster. Further study has suggested that DOCK180 is involved in the activation of Rac by the CrkII-p130(Cas) complex. With the use of deletion mutants of DOCK180, we found that the C-terminal region containing a cluster of basic amino acids was required for binding to and activation of Rac. This region showed high amino-acid sequence similarity to the consensus sequence of the phosphoinositide-binding site; this led us to examine whether this basic region binds to phosphoinositides. For this purpose we used PtdIns(3,4,5)P(3)-APB beads, as reported previously [Shirai, Tanaka, Terada, Sawada, Shirai, Hashimoto, Nagata, Iwamatsu, Okawa, Li et al. (1998) Biochim. Biophys. Acta 1402, 292-302]. By using various competitors, we demonstrated the specific binding of DOCK180 to PtdIns(3,4,5)P(3). The expression of active phosphoinositide 3-kinase (PI-3K) did not enhance a DOCK180-induced increase in GTP-Rac; however, the expression of PI-3K translocated DOCK180 to the plasma membrane. Thus DOCK180 contained a phosphoinositide-binding domain, as did the other guanine nucleotide exchange factors with a Dbl homology domain, and was translocated to the plasma membrane on the activation of PI-3K.
authors.affiliation: Department of Pathology, Research Institute, International Medical Center of Japan, 1-21-1 Toyama, Shinjuku-ku, Tokyo 162-8655, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kobayashi
authors.forename: T
authors.initials: T
authors.lastname: Shirai
authors.forename: E
authors.initials: E
authors.lastname: Kiyokawa
authors.forename: N
authors.initials: N
authors.lastname: Mochizuki
authors.forename: M
authors.initials: M
authors.lastname: Matsuda
authors.forename: Y
authors.initials: Y
authors.lastname: Fukui
mesh_terms: D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: C099818:DOCK1 protein, human; D018129:Phosphatidylinositol Phosphates; D011506:Proteins; C060974:phosphatidylinositol 3,4,5-triphosphate; D020744:rac GTP-Binding Proteins