title: GM3-enriched microdomain involved in cell adhesion and signal transduction through carbohydrate-carbohydrate interaction in mouse melanoma B16 cells.
abstract: Mouse melanoma B16 cells are characterized by the predominant presence of ganglioside GM3 and adhere to lactosylceramide- or Gg3-coated plates through interaction of GM3 with lactosylceramide or Gg3, whereby not only adhesion but also spreading and enhancement of cell motility occur (Kojima, N., Hakomori, S. (1991) J. Biol. Chem. 266, 17552-17558). We now report that the adhesion process is based essentially on a glycosphingolipid-enriched microdomain (GEM) at the B16 cell surface, since >90% of GM3 present in the original cells is found in GEM, and GEM is also enriched in several signal transducer molecules, e.g. c-Src, Ras, Rho, and focal adhesion kinase (FAK). GEM was isolated as a low density membranous fraction by homogenization of B16 cells in lysis buffer under two different conditions (i.e. buffer containing 1% Triton X-100, or hypertonic sodium carbonate without detergent), followed by sucrose density gradient centrifugation. A close association of GM3 with c-Src, Rho, and FAK was indicated by co-immunoprecipitation of GM3 present in GEM by anti-GM3 monoclonal antibody DH2, followed by Western blotting with antibodies directed to these transducer molecules. The following data indicate that GEM is a structural and functional unit for initiation of GM3-dependent cell adhesion coupled with signal transduction. 1) Tyrosine phosphorylation in FAK was greatly enhanced in B16 cells adhered to Gg3-coated plates but was minimal in cells adhered to GM3-coated, GlcCer-coated, or noncoated plates. 2) GTP loading on Ras and Rho increased significantly when cells were adhered to Gg3-coated plates, compared with GM3-coated, GlcCer-coated, or noncoated plates. Since Ras and Rho are closely associated with GM3 in GEM, cell adhesion/stimulation through GM3 in GEM may induce activation of Ras and Rho through enhanced GTP binding.
authors.affiliation: Pacific Northwest Research Foundation, Seattle, Washington 98122, USA.
authors.forename: K
authors.initials: K
authors.lastname: Iwabuchi
authors.forename: S
authors.initials: S
authors.lastname: Yamamura
authors.forename: A
authors.initials: A
authors.lastname: Prinetti
authors.forename: K
authors.initials: K
authors.lastname: Handa
authors.forename: S
authors.initials: S
authors.lastname: Hakomori
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002458:Cell Fractionation; D002462:Cell Membrane / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D004285:Dogs; D004912:Erythrocytes / Q000737:chemistry; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D005679:G(M3) Ganglioside / Q000302:isolation & purification / Q000494:pharmacology / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008546:Melanoma, Experimental / Q000473:pathology / Q000503:physiopathology* / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron; D008954:Models, Biological; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D015815:Cell Adhesion Molecules; D005679:G(M3) Ganglioside; D006153:Guanosine Diphosphate; D019000:Phosphotyrosine; D006160:Guanosine Triphosphate; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D019204:GTP-Binding Proteins