These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: XBP-1 specifically promotes IgM synthesis and secretion, but is dispensable for degradation of glycoproteins in primary B cells.
    Author: Tirosh B, Iwakoshi NN, Glimcher LH, Ploegh HL.
    Journal: J Exp Med; 2005 Aug 15; 202(4):505-16. PubMed ID: 16103408.
    Abstract:
    Differentiation of B cells into plasma cells requires X-box binding protein-1 (XBP-1). In the absence of XBP-1, B cells develop normally, but very little immunoglobulin is secreted. XBP-1 controls the expression of a large set of genes whose products participate in expansion of the endoplasmic reticulum (ER) and in protein trafficking. We define a new role for XBP-1 in exerting selective translational control over high and sustained levels of immunoglobulin M (IgM) synthesis. XBP-1(-/-) and XBP-1(+/+) primary B cells synthesize IgM at comparable levels at the onset of stimulation with lipopolysaccharide or CpG. However, later there is a profound depression in synthesis of IgM in XBP-1(-/-) B cells, notwithstanding similar levels of micromRNA. In marked contrast, lack of XBP-1 does not affect synthesis and trafficking of other glycoproteins, or of immunoglobulin light chains. Contrary to expectation, degradation of proteins from the ER, using TCRalpha or US11-mediated degradation of class I major histocompatibility complex molecules as substrates, is normal in XBP-1(-/-) B cells. Furthermore, degradation of membrane mu was unaffected by enforced expression of XBP-1. We conclude that in primary B cells, the XBP-1 pathway promotes synthesis and secretion of IgM, but does not seem to be involved in the degradation of ER proteins, including that of mu chains themselves.
    [Abstract] [Full Text] [Related] [New Search]