ISSN:
1432-1211
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The membrane immunoglobulin M (m1gM) of a B lymphocyte serves as a receptor for its cognate antigen. Our aim is to elucidate the structure and function of this membrane-bound receptor. The first step is to determine the requirements for proper membrane placement of IgM. We have used mIgM-positive B lymphocyte tumors from which we isolated mIgM negative variants by immunoselection. We report here the initial characterization of mIgM-variants isolated by repeated cycles of selection of the murine B lymphoma, WEHI 279.1, with goat anti-mouse immunoglobulin (GαMIg) and complement. These particular variants were chosen from a pool of more than 150 variants originally isolated because they resulted from several selection schemes and clearly had different origins. By analysis of their proteins, we have found three major phenotypes that do not produce mIgM: reduced μm, μs and L chain levels within cells, loss of μm and μs but retention of L chain synthesis, and loss of μm but retention of reduced amounts of μs and L chain. The defects underlying these phenotypes produce complex changes in the synthesis, turnover, and secretion of the μ or L chains involved. We performed experiments comparing the effects of the glycosylation inhibitor tunicamycin on variants with reduced p and L levels with its effects on variants with L but no μ chains. These experiments suggested that μ and L chain synthesis are controlled coordinately at the level of protein synthesis. We have not yet isolated any variants lacking L chain synthesis or any appearing to have gross structural defects in the μs protein. This analysis is the first phase of the detailed characterization of the requirements for proper synthesis, processing, tetramer formation, and membrane display of mIgM on B lymphoma tumors in mice.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00364758
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