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

R. Amitay, S. Bar-Nun, J. Haimovich, E. Rabinovich, I. Shachar

Research output: Contribution to journalArticlepeer-review

Abstract

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 μ chain over the expressed membrane μ 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.

Original languageEnglish
Pages (from-to)12568-12573
Number of pages6
JournalJournal of Biological Chemistry
Volume266
Issue number19
StatePublished - 1991

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