Glucose-regulated protein 78 kDa (GRP78), also known as heat shock 70 kDa protein 5 (HspA5) and immunoglobulin heavy chain-binding protein (BiP), is a glucose-regulated protein that is constitutively expressed in the lumen of the endoplasmic reticulum (ER).1,2,3 It is composed of two functional domains, an N-terminal nucleotide-binding domain that contains an ATP catalytic site and a C-terminal substrate binding domain that binds hydrophobic polypeptides.4 GRP78 functions as a molecular chaperone, assisting in the translocation of polypeptides from the cytosol into the ER, folding of nascent polypeptides, as well as refolding and preventing aggregation of misfolded proteins. It also plays a role in the ER-assisted degradation (ERAD) and unfolded protein response (UPR) pathways.5,6 GRP78 chaperone activity is driven by an ATPase cycle that is regulated by ER-localized DnaJ-like protein co-factors and nuclear exchange factors.7,8 Expression of GRP78 is upregulated in response to ER stress caused by viral and bacterial infections as well as various cancers.9 ER stress can also promote extracellular secretion of GRP78 leading to its anti-inflammatory functions in immunity.10WARNING This product is not for human or veterinary use.
