Protein: XBP1_HUMAN
Sequence: MVVVAAAPNPADGTPKVLLLSGQPASAAGAPAGQALPLMVPAQRGASPEAASGGLPQARKRQRLTHLSPEEKALRRKLKNRVAAQTARDRKKARMSELEQQVVDLEEENQKLLLENQLLREKTHGLVVENQELRQRLGMDALVAEEEAEAKGNEVRPVAGSAESAALRLRAPLQQVQAQLSPLQNISPWILAVLTLQIQSLISCWAFWTTWTQSCSSNALPQSLPAWRSSQRSTQKDPVPYQPPFLCQWGRHQPSWKPLMN
What is the function of this protein?
Functions as a stress-inducible potent transcriptional activator during endoplasmic reticulum (ER) stress by inducing unfolded protein response (UPR) target genes via binding to the UPR element (UPRE).  Up-regulates target genes encoding ER chaperones and ER-associated degradation (ERAD) components to enhance the capacity of productive folding and degradation mechanism, respectively, in order to maintain the homeostasis of the ER under ER stress (PubMed:11779464, PubMed:25239945).  Plays a role in the production of immunoglobulins and interleukin-6 in the presence of stimuli required for plasma cell differentiation (By similarity).  Induces phospholipid biosynthesis and ER expansion (PubMed:15466483).  Contributes to the VEGF-induced endothelial cell (EC) growth and proliferation in a Akt/GSK-dependent and/or -independent signaling pathway, respectively, leading to beta-catenin nuclear translocation and E2F2 gene expression (PubMed:23529610).  Promotes umbilical vein EC apoptosis and atherosclerotisis development in a caspase-dependent signaling pathway, and contributes to VEGF-induced EC proliferation and angiogenesis in adult tissues under ischemic conditions (PubMed:19416856, PubMed:23529610).  Involved in the regulation of endostatin-induced autophagy in EC through BECN1 transcriptional activation (PubMed:23184933).  Plays a role as an oncogene by promoting tumor progression: stimulates zinc finger protein SNAI1 transcription to induce epithelial-to-mesenchymal (EMT) transition, cell migration and invasion of breast cancer cells (PubMed:25280941).  Involved in adipocyte differentiation by regulating lipogenic gene expression during lactation.  Plays a role in the survival of both dopaminergic neurons of the substantia nigra pars compacta (SNpc), by maintaining protein homeostasis and of myeloma cells.  Increases insulin sensitivity in the liver as a response to a high carbohydrate diet, resulting in improved glucose tolerance.  Improves also glucose homeostasis in an ER stress- and/or insulin-independent manner through both binding and proteasome-induced degradation of the transcription factor FOXO1, hence resulting in suppression of gluconeogenic genes expression and in a reduction of blood glucose levels.  Controls the induction of de novo fatty acid synthesis in hepatocytes by regulating the expression of a subset of lipogenic genes in an ER stress- and UPR-independent manner (By similarity).  Associates preferentially to the HDAC3 gene promoter region in a disturbed flow-dependent manner (PubMed:25190803).  Binds to the BECN1 gene promoter region (PubMed:23184933).  Binds to the CDH5/VE-cadherin gene promoter region (PubMed:19416856).  Binds to the ER stress response element (ERSE) upon ER stress (PubMed:11779464).  Binds to the 5'-CCACG-3' motif in the PPARG promoter (By similarity).
What are the official names of this protein?
X-box-binding protein 1, XBP-1, Tax-responsive element-binding protein 5, TREB-5.
What is the protein family that this protein belongs to?
Belongs to the bZIP family.
What are the subcellular locations of this protein?
Endoplasmic reticulum. Note=Colocalizes with ERN1 and KDR in the endoplasmic reticulum in endothelial cells in a vascular endothelial growth factor (VEGF)-dependent manner (PubMed:23529610). SUBCELLULAR LOCATION: [Isoform 1]: Nucleus. Cytoplasm. Endoplasmic reticulum membrane; Single-pass type II membrane protein. Endoplasmic reticulum membrane; Peripheral membrane protein. Membrane; Peripheral membrane protein. Note=Shows no preferential localization to either the nucleus or the cytoplasm (By similarity). Shuttles between the nucleus and the cytoplasm in a CRM1- dependent manner (PubMed:16461360). Localizes predominantly at the endoplasmic reticulum membrane as a membrane-spanning protein; whereas may be only marginally localized on the cytosolic side of the ER membrane as a peripheral membrane (PubMed:19394296, PubMed:25190803). SUBCELLULAR LOCATION: [Isoform 2]: Nucleus. Cytoplasm. Note=Localizes predominantly in the nucleus. Colocalizes in the nucleus with SIRT1. Translocates into the nucleus in a PIK3R-, ER stress-induced- and/or insulin-dependent manner (By similarity). SUBCELLULAR LOCATION: [X-box-binding protein 1, cytoplasmic form]: Cytoplasm. Nucleus. Note=Localizes in the cytoplasm and nucleus after HM13/SPP-mediated intramembranaire proteolytic cleavage of isoform 1 (PubMed:25239945).