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Assembled Pre-B Cell Receptor Complexes Are Retained in the Endoplasmic Reticulum by a Mechanism That Is Not Selective for the Pseudo-light Chain
The pre-B cell receptor (BCR) complex, consisting of μ heavy chain, a pseudo-light chain, and the Mb-1/B29 heterodimer, directs the transition to the mature B cell stage. Plasma membrane expression of the pre-BCR is extremely low, despite its presumed signaling function. We have compared assembly a...
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Published in: | The Journal of biological chemistry 1996-08, Vol.271 (32), p.19272-19278 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The pre-B cell receptor (BCR) complex, consisting of μ heavy chain, a pseudo-light chain, and the Mb-1/B29 heterodimer, directs
the transition to the mature B cell stage. Plasma membrane expression of the pre-BCR is extremely low, despite its presumed
signaling function. We have compared assembly and intracellular transport of the pre-BCR complex with that of the BCR complex
in mature B cells. Synthesis and assembly rate of pre-BCR and BCR components are comparable. However, the pre-BCR is subject
to a highly efficient retention mechanism, which only allows exit of a few percent of the complexes from the endoplasmic reticulum
(ER). This small transported pool of pre-BCR complexes is significantly enriched for protein-tyrosine kinase activity, as
compared with the ER-localized receptor pool. Accordingly, the Src-related tyrosine kinase Lyn was found in the transported
glycoprotein fraction but not in association with ER-localized glycoproteins. Upon introduction of a conventional light chain
into pre-B cells, plasma membrane receptor levels increased, but the efficiency of intracellular transport of the receptor
complex was not restored to that in mature B cells. This indicates that the ER retention mechanism is not selective for the
pseudo-light chain and may be inherent to pre-B cells. We propose that this retention mechanism contributes to the regulation
of pre-BCR-mediated signal transduction. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.271.32.19272 |