RRC ID 12192
Author Arai A, Nosaka Y, Kohsaka H, Miyasaka N, Miura O.
Title CrkL activates integrin-mediated hematopoietic cell adhesion through the guanine nucleotide exchange factor C3G.
Journal Blood
Abstract CrkL is a member of the Crk family of adapter proteins consisting mostly of SH2 and SH3 domains. CrkL is most abundantly expressed in hematopoietic cells and has been implicated in pathogenesis of chronic myelogenous leukemia. However, its function has not been precisely defined. Here, we show that overexpression of CrkL enhances the adhesion of hematopoietic 32D cells to fibronectin. The CrkL-induced increase in cell adhesion was blocked by antibodies against VLA-4 (alpha4beta1) and VLA-5 (alpha5beta1) but was observed without changes in surface expression levels of these integrins. Studies using CrkL mutants demonstrated that the SH2 domain is partially required for enhancing cell adhesion, whereas the C-terminal SH3 domain as well as the tyrosine phosphorylation site (Y207) is dispensable. In contrast, the N-terminal SH3 domain, involved in binding C3G and other signaling molecules, was showed to play a crucial role, because a mutant defective of this domain showed an inhibitory effect on the cell adhesion to fibronectin. Furthermore, overexpression of C3G also increased the adhesion of hematopoietic cells to fibronectin, whereas a C3G mutant lacking the guanine nucleotide exchange domain abrogated the CrkL-induced increase in cell adhesion. On the other hand, a dominant negative mutant of H-Ras or that of Raf-1 enhanced the basal and CrkL-induced cell adhesion and that of R-Ras modestly decreased the adhesion. Taken together, these results indicate that the CrkL-C3G complex activates VLA-4 and VLA-5 in hematopoietic cells, possibly by activating the small GTP binding proteins, including R-Ras, through the guanine nucleotide exchange activity of C3G.
Volume 93(11)
Pages 3713-22
Published 1999-6-1
PII S0006-4971(20)59502-5
PMID 10339478
MeSH Adaptor Proteins, Signal Transducing* Animals Cell Adhesion / physiology Cell Line Fibronectins Gene Expression Regulation / physiology Guanine Nucleotide Exchange Factors Hematopoiesis* Hematopoietic Stem Cells / cytology* Hematopoietic Stem Cells / physiology* Humans Integrin alpha4beta1 Integrins / physiology* Mice Nuclear Proteins / physiology* Proteins / physiology* Receptors, Fibronectin / physiology* Receptors, Lymphocyte Homing / physiology* Signal Transduction / physiology ras Guanine Nucleotide Exchange Factors src Homology Domains
IF 17.794
Times Cited 75
DNA material pHSG-C3G Human C3G (RDB01595)