title: Hyaluronan promotes CD44v3-Vav2 interaction with Grb2-p185(HER2) and induces Rac1 and Ras signaling during ovarian tumor cell migration and growth.
abstract: In this study we initially examined the interaction between CD44v3 (a hyaluronan (HA) receptor) and Vav2 (a guanine nucleotide exchange factor) in human ovarian tumor cells (SK-OV-3.ipl cell line). Immunological data indicate that both CD44v3 and Vav2 are expressed in SK-OV-3.ipl cells and that these two proteins are physically linked as a complex in vivo. By using recombinant fragments of Vav2 and in vitro binding assays, we have detected a specific binding interaction between the SH3-SH2-SH3 domain of Vav2 and the cytoplasmic domain of CD44. In addition, we have observed that the binding of HA to CD44v3 activates Vav2-mediated Rac1 signaling leading to ovarian tumor cell migration. Further analyses indicate that the adaptor molecule, growth factor receptor-bound protein 2 (Grb2) that is bound to p185(HER2) (an oncogene product), is also associated with the CD44v3-Vav2 complex. HA binding to SK-OV-3.ipl cells promotes recruitment of both Grb2 and p185(HER2) to the CD44v3-Vav2 complex leading to Ras activation and ovarian tumor cell growth. In order to determine the role of Grb2 in CD44v3 signaling, we have transfected SK-OV-3.ipl cells with Grb2 mutant cDNAs (e.g. Delta N-Grb2 that has a deletion in the amino-terminal SH3 domain or Delta C-Grb2 that has a deletion in the carboxyl-terminal SH3 domain). Our results clearly indicate that the SH3 domain deletion mutants of Grb2 (i.e. the Delta N-Grb2 (and to a lesser extent the Delta C-Grb2) mutant) not only block their association with p185(HER2) but also significantly impair their binding to the CD44v3-Vav2 complex and inhibit HA/CD44v3-induced ovarian tumor cell behaviors. Taken together, these findings strongly suggest that the interaction of CD44v3-Vav2 with Grb2-p185(HER2) plays an important role in the co-activation of both Rac1 and Ras signaling that is required for HA-mediated human ovarian tumor progression.
authors.affiliation: Enocrine Unit, Department of Medicine, University of California and Veterans Affairs Medical Center, San Francisco, California 94121, USA. lillyb@itsa.ucsf.edu
authors.forename: L Y
authors.initials: LY
authors.lastname: Bourguignon
authors.forename: H
authors.initials: H
authors.lastname: Zhu
authors.forename: B
authors.initials: B
authors.lastname: Zhou
authors.forename: F
authors.initials: F
authors.lastname: Diedrich
authors.forename: P A
authors.initials: PA
authors.lastname: Singleton
authors.forename: M C
authors.initials: MC
authors.lastname: Hung
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D005260:Female; D051380:GRB2 Adaptor Protein; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000378:metabolism*; D008954:Models, Biological; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D010051:Ovarian Neoplasms / Q000378:metabolism / Q000473:pathology; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav; D011869:Radioligand Assay; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020703:ras GTPase-Activating Proteins / Q000378:metabolism; D018909:src Homology Domains / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D051380:GRB2 Adaptor Protein; D020662:Guanine Nucleotide Exchange Factors; D006160:Guanosine Triphosphate; D018960:Hyaluronan Receptors; D006820:Hyaluronic Acid; D015513:Oncogene Proteins; D011506:Proteins; D051567:Proto-Oncogene Proteins c-vav; D018719:Erb-b2 Receptor Tyrosine Kinases; D020830:rac1 GTP-Binding Protein; D020703:ras GTPase-Activating Proteins; C121450:CD44V3,8-10; C495948:GRB2 protein, human; C093651:VAV2 protein, human