Post-translational regulation of IgM expression in B lymphocytes. Selective nonlysosomal degradation of assembled secretory IgM is temperature-dependent and occurs prior to the trans-Golgi

B cells express on their surface the membrane form of IgM (mIgM). Upon differentiation, the resulting plasma cells synthesize and secrete large amounts of the secretory form of IgM (sIgM). Surprisingly, B lymphocytes synthesize an excess of secretory mu chain over the expressed membrane mu chain. Ho...

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Bibliographic Details
Published in:The Journal of biological chemistry 1991-07, Vol.266 (19), p.12568-12573
Main Authors: Amitay, R., Bar-Nun, S., Haimovich, J., Rabinovich, E., Shachar, I.
Format: Article
Language:English
Subjects:
Animals
B-Lymphocytes - metabolism
Blotting, Northern
Chloroquine - pharmacology
Electrophoresis, Polyacrylamide Gel
Gene Expression Regulation
Golgi Apparatus - metabolism
Hexosaminidases
Immunoglobulin M - genetics
Lymphoma, B-Cell - metabolism
Lysosomes - metabolism
Mice
Monensin - pharmacology
Precipitin Tests
Protein Processing, Post-Translational
RNA - analysis
Temperature
Tumor Cells, Cultured
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Summary:B cells express on their surface the membrane form of IgM (mIgM). Upon differentiation, the resulting plasma cells synthesize and secrete large amounts of the secretory form of IgM (sIgM). Surprisingly, B lymphocytes synthesize an excess of secretory mu chain over the expressed membrane mu chain. However, the sIgM is degraded intracellularly, indicating regulation of IgM expression at the post-translational level. In the present report, we show that the assembly, maturation, and degradation of IgM in 38C B lymphocytes are highly accelerated above a certain threshold temperature. Furthermore, the degradation of sIgM is delayed and takes place by the time the maturation of mIgM in the trans-Golgi is almost completed. Neither chloroquine nor monensin has any effect on this degradation, demonstrating a nonlysosomal pre-trans-Golgi process. In addition, the degradation is of endoglycosidase H-sensitive assembled sIgM molecules. We conclude that the degradation of sIgM in 38C B lymphocytes is a postendoplasmic reticulum, pre-trans-Golgi process. We suggest that this degradation process plays a role in the post-translational regulation of expression of soluble lumenal sIgM.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(18)98936-2