The immunoglobulin light chain related protein lambda 5 is expressed on the surface of mouse pre-B cell lines and can function as a signal transducing molecule.
Abelson Leukemia Virus-transformed mouse cell lines with an early pre-B phenotype carry partially rearranged or unrearranged Ig-H genes and consequently do not express intact IgM-H protein (mu protein). Such early mu- pre-B cells express an intracellular protein complex of the pre-B cell specific 22 kDa protein lambda 5 and a 16 kDa protein designated p16. Late pre-B cell lines which carry a rearranged IgM-H chain gene in which a continuous translational reading frame has been established in the fused V-D-J element express intact mu-protein, which forms an intracellular complex with lambda 5 and p16. We show here that both the lambda 5/p16 or the mu/lambda 5/p16 complexes can be immunoprecipitated from lysates of cells surface labeled with 125I. Thus early pre-B cells express the lambda 5/p16 complex on the cell surface in the absence of mu protein, while mu+ late pre-B cells express a surface mu/lambda 5/p16 complex. To investigate a possible signal transduction function of the lambda 5/p16 and mu/lambda 5/p16 complexes on the surface of pre-B cell lines we measured the changes in intracellular free Ca2+ after treatment of cells with anti-lambda 5 or anti-mu antibodies. Two mu- early pre-B cell lines showed a rapid and transient increase in intracellular free Ca2+ when incubated with anti-lambda 5 antibodies but not when incubated with anti-mu, while the mu+ late pre-B cell line CB32 showed a rapid and transient increase in intracellular Ca2+ after incubation with anti-lambda 5 or anti-mu. These results show that both the lambda 5/p16 and the mu/lambda 5/p16 cell surface protein complexes can transduce an external signal to the inside of the cell, which implicates these complexes in the regulation of pre-B cell physiology.
Misener
V
V
Department of Immunology, University of Toronto, Ontario, Canada.
Downey
G P
GP
Jongstra
J
J
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002461:Cell Line, Transformed; D006412:Hematopoietic Stem Cells / Q000276:immunology; D007146:Immunoglobulin lambda-Chains / Q000276:immunology* / Q000378:metabolism; D007148:Immunoglobulin mu-Chains / Q000378:metabolism; D051379:Mice; D011947:Receptors, Antigen, B-Cell / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*
D007146:Immunoglobulin lambda-Chains; D007148:Immunoglobulin mu-Chains; D011947:Receptors, Antigen, B-Cell