Anti-XBP-1 Monoclonal Antibody [3H1G4]

X box binding protein 1 (XBP-1) is a key protein in the mammalian unfolded protein response (UPR) that protects the cell against the stress of malfolded proteins in the endoplasmic reticulum (ER) . Upon sensing unfolded proteins, an ER transmembrane endonuclease and kinase termed IRE1p is activated and excises an intron from XBP-1 mRNA. The spliced XBP-1 mRNA results in a 371 amino acid protein (XBP-1s) which is then translocated to the nucleus where it binds to the regulatory elements of downstream genes. Together with other UPR transcription factors such as ATF6, XBP-1 stimulates the production of ER stress proteins including the ER resident protein chaperones glucose regulated protein (GRP) 78 and GRP94.

Expressed in plasma cells in rheumatoid synovium (PubMed:11460154) . Over-expressed in primary breast cancer and metastatic breast cancer cells (PubMed:25280941) . Isoform 1 and isoform 2 are expressed at higher level in proliferating as compared to confluent quiescent endothelial cells (PubMed:19416856) .

Functions as a transcription factor during endoplasmic reticulum (ER) stress by regulating the unfolded protein response (UPR) . Required for cardiac myogenesis and hepatogenesis during embryonic development, and the development of secretory tissues such as exocrine pancreas and salivary gland (By similarity) . Involved in terminal differentiation of B lymphocytes to plasma cells and production of immunoglobulins (PubMed:11460154) . Modulates the cellular response to ER stress in a PIK3R-dependent manner (PubMed:20348923) . Binds to the cis-acting X box present in the promoter regions of major histocompatibility complex class II genes (PubMed:8349596) . Involved in VEGF-induced endothelial cell (EC) proliferation and retinal blood vessel formation during embryonic development but also for angiogenesis in adult tissues under ischemic conditions. Functions also as a major regulator of the UPR in obesity-induced insulin resistance and type 2 diabetes for the management of obesity and diabetes prevention (By similarity) .