Thy-1 molecule associates with protein tyrosine kinase(s) in rat mesangial cells

Glycophosphatidylinositol (GPI)-linked Thy-1 molecules, well known cell surface markers of murine T cells, are present on the glomerular mesangial cells of the rat kidney. The administration of anti-Thy-1.1 MoAbs 1-22-3 and OX-7 to rats induces severe and mild complement-dependent mesangial proliferative glomerulonephritis, respectively. In order to determine whether protein-tyrosine kinase (PTK) activity is associated with Thy-1 molecules on rat mesangial cell surface, we performed an immune complex kinase assay, using anti-Thy-1 MoAbs 1-22-3 and OX-7, followed by reimmunoprecipitation with anti-phosphotyrosine, anti-fyn, anti-lck and anti-lyn antibodies. Physical association of PTK, p59(fyn) and p56/53(lyn) with Thy-1 molecules was demonstated in cultured rat mesangial cells. The activities of these kinases detected in MoAb 1-22-3 precipitates were higher than those in MoAb OX-7 precipitates. These results suggest that Thy-1 molecule transduces some signals also in rat mesangial cells.