Electron micrograph of a mature plasma cell showing extensive endoplasmic reticulum. Reproduced from Bosman et al. (1969. J. Exp. Med. 129:1029–1044).

The development of antibody-secreting plasma cells is crippled in the absence of the transcription factor XBP-1 (X-box binding protein). Based on the role of XBP-1 in the endoplasmic reticulum (ER) unfolded protein response (UPR), it was speculated that the ER needs this protein to cope with the ramped-up protein production that accompanies plasma cell differentiation. On page 505, Tirosh and coworkers show instead that XBP-1 controls immunoglobulin synthesis posttranslationally, independently of its role in orchestrating the UPR.

The UPR is a signaling system that ensures proper folding, processing, and degradation of proteins in the ER. When protein production exceeds the ER's quality control capacity, XBP-1 drives the expression of additional proteins, such as chaperones and degradative enzymes that help to absorb the extra...

The Rockefeller University Press
2005
The Rockefeller University Press
2005
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