ASSOCIATION OF CD24 WITH THE KINASE C-FGR IN A SMALL-CELL LUNG-CANCERCELL-LINE AND WITH THE KINASE LYN IN AN ERYTHROLEUKEMIA CELL-LINE

Human CD24 is a highly glycosylated glycosylphosphatidylinositol-linke d (GPI-linked) cell surface protein. GPI linkeded proteins are involve d in signal transduction mediated by members of the protein tyrosine k inase (PTK) family. Therefore we studied associated molecules providin g the signaling capacity of CD24. Lysates of SW2 and K562 cells were a nalysed for expression of PTK of the c-src family by Western blotting. We identified c-fgr in SW2 lysates and c-fgr and also lyn in K562 lys ates. To study a putative association of these PTK with CD24 we perfor med immunoprecipitations with the mAb SWA11 directed against CD24. Wes tern analysis of the precipitates showed an association of c-fgr with CD24 in SW2 cells and lyn in K562 cells. We conclude that either c-fgr or lyn is physically associated with CD24 in a cell-type depending ma nner. An involvement of these complexes in signaling phenomenons of CD 24 in small cell lung cancer and in leukaemias is discussed. (C) 1996 Academic Press, Inc.