X-box binding protein 1

XBP1 is the acronym for "X-Box-Binding Protein 1", a protein encoding the gene of the same name located on chromosome 22q12.1.

The expression of the XBP1 protein is controlled by the cytokine IL-4, among others. XBP1 in turn controls the expression of IL-6, a cytokine involved in the growth and differentiation of plasma cells. As part of theunfolded protein response, the XBP1 mRNA is unconventionally spliced in the cytoplasm to produce a mature mRNA. The unspliced XBP1 mRNA encodes XBP1U, a protein that negatively regulates XBP1S and terminates the ER stress response (AragonT et al. (2009). A deletion of Xbp1 induces Paneth cell-specific autophagy and can lead to spontaneous ileitis (Adolph et al. 2013).

Unfolded Protein Response" is a protective mechanism of the cell coupled to the endoplasmic reticulum (ER), which is caused by the accumulation of misfolded proteins in the endoplasmic reticulum (Kozutsumi Y et al. 1988). A misregulation of this protein quality control by UPR can be the cause of numerous diseases.

1. Adolph TE et al (w2013) Paneth cells as a site of origin for intestinal inflammation. Nature 503: 272-276
2. AragonT et al (2009) Messenger RNA targeting to endoplasmic reticulum stress signalling sites. Nature 457: 736-740
3. Calfon M et al (2002) IRE1 couples endoplasmic reticulum load to secretory capacity by processing the XBP-1 mRNA. Nature 415: 92-96
4. Kozutsumi Y et al (1988) The presence of malfolded proteins in the endoplasmic reticulum signals the induction of glucose-regulated proteins. Nature 332: 462-464