Isolation and characterization of a B lymphocyte mutant with altered signal transduction through its antigen receptor.
A receptor surface Ig (sIg) signaling variant of WEHI-231 was constructed to investigate components and linkages between various signaling events associated with signal transduction through sIg. Unlike the wildtype, crosslinking of sIgM on VS2.12-cl.2 did not result in downregulation of proliferation. Similarly, receptor crosslinking was uncoupled from inositol phospholipid (PI) hydrolysis and upregulation of c-fos expression in the variant. The signaling defect in VS2.12-cl.2 appears to be proximal to phospholipase C activation as direct G protein activation by A1F4- triggers PI hydrolysis and bypassing PI hydrolysis using phorbol diester stimulation of protein kinase C restores the inhibitable phenotype and the ability to upregulate c-fos. Even more interesting, sIg-linked Ca2+ responses by VS2.12-cl.2 are equivalent to these observed in the wildtype WEHI-231. These latter results suggest that contrary to current thought, sIg-generated signals may not be coupled to Ca2+ fluxes entirely via inositol phospholipid hydrolysis. Thus, VS2.12-cl.2 is a new and powerful tool with which to analyze signaling through sIg at the molecular level.
Monroe
J G
JG
Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104.
Seyfert
V L
VL
Owen
C S
CS
Sykes
N
N
D000906:Antibodies; D001402:B-Lymphocytes / Q000276:immunology*; D002118:Calcium / Q000378:metabolism; D003432:Cross-Linking Reagents; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000502:physiology; D006868:Hydrolysis; D007075:Immunoglobulin M / Q000032:analysis / Q000235:genetics / Q000276:immunology; D007148:Immunoglobulin mu-Chains / Q000276:immunology; D007163:Immunosorbent Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D008223:Lymphoma; D009154:Mutation; D010716:Phosphatidylinositols / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016760:Proto-Oncogene Proteins c-fos; D011947:Receptors, Antigen, B-Cell / Q000235:genetics*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
D000906:Antibodies; D003432:Cross-Linking Reagents; D007075:Immunoglobulin M; D007148:Immunoglobulin mu-Chains; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D011947:Receptors, Antigen, B-Cell; D011493:Protein Kinase C; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium