Mouse CD24 as a signaling molecule for integrin-mediated cell binding: functional and physical association with src-kinases.
CD24 is a differentiation antigen expressed by murine hematopoietic and neural cells which is linked to the membrane via a glycosylphosphatidylinositol (GPI) anchor. In monocytic ESb-MP cells the molecule serves as a ligand for P-selectin and triggering with CD24 specific antibodies can activate VLA-5/L1-mediated cell adhesion in these cells. We report here that the aggregation is specific for CD24 and not seen with antibodies to the GPI-anchored molecule Thy-1. The Tyr-kinase inhibitor herbimycin can block the aggregation. We studied CD24 associated molecules that might be involved in signal transduction. Antibodymediated crosslinking of CD24 induced a rapid Tyr-phosphorylation of several cellular proteins in ESb-MP cells which correlated with an elevated activity of p56lck but not p60fyn or MAP-1 kinase. Several phosphorylated proteins were co-immunoprecipitated with CD24. Re-immunoprecipitation allowed the detection of p56lck, p56hck, and p54lyn but not p60fyn, PI-3k, or PLCgamma as a compenent of the CD24 detergent resistant complex. It is suggested that the CD24-associated kinases are involved in the activation of cell aggregation.
Sammar
M
M
Tumor Immunology Programme, German Cancer Research Center, Heidelberg. m.sammar@dkfz-heidelberg.de
Gulbins
E
E
Hilbert
K
K
Lang
F
F
Altevogt
P
P
D000818:Animals; D000906:Antibodies; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism*; D051927:CD24 Antigen; D002449:Cell Aggregation; D002460:Cell Line; D003432:Cross-Linking Reagents; D004789:Enzyme Activation; D016023:Integrins / Q000378:metabolism*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008562:Membrane Glycoproteins; D051379:Mice; D015394:Molecular Structure; D008970:Molecular Weight; D009000:Monocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism*
D000906:Antibodies; D015703:Antigens, CD; D051927:CD24 Antigen; C497890:Cd24a protein, mouse; D003432:Cross-Linking Reagents; D016023:Integrins; D008562:Membrane Glycoproteins; D010750:Phosphoproteins; D014443:Tyrosine; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D019061:src-Family Kinases