title: Stimulation of tyrosine phosphorylation of distinct proteins in response to antibody-mediated ligation and clustering of alpha 3 and alpha 6 integrins.
abstract: The interaction of cells with components of the extracellular matrix through their integrin receptors results in the stimulation of tyrosine phosphorylation of several proteins, suggesting that these receptors play a key role in signal transduction. Here we report that antibody-mediated ligation and clustering of alpha 3 beta 1 and alpha 6 beta 1/alpha 6 beta 4 integrins resulted in the stimulation of tyrosine phosphorylation of proteins that are specific for each heterodimer. Thus, ligation and clustering of the alpha 3 beta 1 integrin on human prostate carcinoma cells (PC-3) and human umbilical vein endothelial cells (HUVEC) with anti-alpha 3 antibodies resulted in the stimulation of tyrosine phosphorylation of a 55 kDa protein. In contrast, ligation and clustering of the alpha 6 beta 1 integrin on these cells with anti-alpha 6 antibody resulted in the dramatic stimulation of tyrosine phosphorylation of a 90 kDa protein in addition to a 52 kDa protein, and ligation and clustering of alpha 5 beta 1 on HUVEC did not result in the apparent stimulation of tyrosine phosphorylation of any proteins. Clustering with anti-beta 1 antibodies triggered the tyrosine phosphorylation of all of these proteins, whereas ligation and clustering of PC-3 cells with an anti-beta 4 antibody resulted in the tyrosine phosphorylation of a distinct 62 kDa protein. Since the PC-3 cells express both alpha 6 beta 1 and alpha 6 beta 4, these data suggest that these two receptors can transduce distinct signals. All of the phosphorylations could be inhibited by treating the cells with Genistein, a tyrosine kinase inhibitor. Antibody-mediated ligation and clustering of integrins on the two types of cells did not result in the stimulation of tyrosine phosphorylation of pp125 focal adhesion kinase, although this was observed upon cell attachment and spreading on fibronectin, laminin and anti-alpha 3 monoclonal antibody. Collectively, these data demonstrate that cross-linking of different integrin heterodimers can stimulate tyrosine kinase activities, leading to the phosphorylation of distinct proteins, which are also different from those observed when cells are allowed to spread on a matrix.
authors.affiliation: Cancer Research Program, Sunnybrook Health Science Centre, Toronto, Ontario, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Jewell
authors.forename: C
authors.initials: C
authors.lastname: Kapron-Bras
authors.forename: P
authors.initials: P
authors.lastname: Jeevaratnam
authors.forename: S
authors.initials: S
authors.lastname: Dedhar
mesh_terms: D000906:Antibodies; D000954:Antigens, Surface / Q000276:immunology / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D004730:Endothelium, Vascular / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D039201:Integrin alpha3beta1; D039121:Integrin alpha6beta1; D039161:Integrin alpha6beta4; D016023:Integrins / Q000276:immunology / Q000378:metabolism*; D008297:Male; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D000906:Antibodies; D000954:Antigens, Surface; D015815:Cell Adhesion Molecules; D003432:Cross-Linking Reagents; D039201:Integrin alpha3beta1; D039121:Integrin alpha6beta1; D039161:Integrin alpha6beta4; D016023:Integrins; D011506:Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human