Surface mu heavy chain expressed on pre-B lymphomas transduces Ca2+ signals but fails to cause growth arrest of pre-B lymphomas.
Little is known about the role of signals transduced by cell surface IgM (sIgM) expressed during early B cell development. A subclone (1.6) of the late pre-B cell lymphoma 70Z/3.12 was used to study signal transduction by surface mu heavy (H) chain before and after transition to the early immature B cell stage, and the functional consequences thereof. Although kappa L chain expression can be induced on 1.6 cells by LPS or cytokines, immunoprecipitations indicated that the non-induced 1.6 cells expressed mu H chain with an alternative protein(s) which may be a surrogate light chain(s). Consistent with this, anti-mu but not anti-kappa or anti-lambda antibodies caused transient Ca2+ mobilization in noninduced 1.6 cells. The Ca2+ signal was derived from both intracellular stores and Ca2+ influx in either noninduced cells or in cells that had been preinduced to express kappa L chain. Thus, the ability of mu H chain to mobilize Ca2+ as a second messenger does not depend upon the expression of mature L chains. The immature B lymphomas, WEHI-231 and CH1, express mature forms of IgM and undergo growth arrest when stimulated by anti-mu antibody. In contrast, signals generated by mu H chain on either noninduced or preinduced 1.6 cells or in the sIgM+ pre-B cell transfectant 300-19 mu lambda 36/8 did not cause growth arrest. These results suggest that mu H chain expressed on pre-B cells is capable of mobilizing Ca2+, but that this signal alone is insufficient to induce growth arrest in the pre-B cell.
Tsutsumi
A
A
Department of Molecular Immunology, Syntex Research, Palo Alto, California 94304.
Terajima
J
J
Jung
W
W
Ransom
J
J
D001402:B-Lymphocytes / Q000166:cytology / Q000502:physiology*; D015152:Blotting, Northern; D002118:Calcium / Q000502:physiology*; D002454:Cell Differentiation; D002455:Cell Division; D015870:Gene Expression; D005803:Genes, Immunoglobulin; D006801:Humans; D007147:Immunoglobulin Light Chains; D054444:Immunoglobulin Light Chains, Surrogate; D007145:Immunoglobulin kappa-Chains / Q000235:genetics; D007148:Immunoglobulin mu-Chains / Q000502:physiology*; D066298:In Vitro Techniques; D008070:Lipopolysaccharides; D008213:Lymphocyte Activation; D016393:Lymphoma, B-Cell / Q000503:physiopathology; D008562:Membrane Glycoproteins / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D011940:Receptor Aggregation; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D015290:Second Messenger Systems; D015398:Signal Transduction; D014162:Transfection; D014407:Tumor Cells, Cultured
D007147:Immunoglobulin Light Chains; D054444:Immunoglobulin Light Chains, Surrogate; D007145:Immunoglobulin kappa-Chains; D007148:Immunoglobulin mu-Chains; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell; D002118:Calcium