Glucose-regulated protein 78 (GRP78) (GRP78)

Glucose-regulated protein 78 (GRP78), also known as BiP or HSPA5, is a major endoplasmic reticulum (ER) chaperone protein belonging to the heat shock protein 70 family [1]. While primarily localized in the ER lumen to assist in protein folding and the unfolded protein response (UPR), GRP78 translocates to the cell surface (csGRP78) under conditions of cellular stress, such as hypoxia or nutrient deprivation, which are common in the tumor microenvironment [2, 3]. On the cell surface of proliferating endothelial cells and cancer cells, csGRP78 acts as a signaling receptor that promotes cell survival, proliferation, and angiogenesis by activating pathways like PI3K/Akt [3, 4]. This preferential expression on stressed cells makes it an attractive therapeutic target for cancer treatment, allowing for selective delivery of cytotoxins or targeted antibodies [2, 5]. Therapeutic strategies include monoclonal antibodies that block its signaling or induce cell death, and peptide-drug conjugates that exploit csGRP78 for internalized drug delivery [5, 6]. Because csGRP78 is specifically upregulated on the surface of tumor-associated vasculature and malignant cells, it serves as a promising biomarker and target for anti-angiogenic and anti-tumor therapies [3, 4]. (Citations: [1] UniProt P11021; [2] Lee, A. S., Nat Rev Cancer 2014; [3] Arap, M. A., et al., Cancer Cell 2004; [4] Gonzalez-Gronow, M., et al., Antioxid Redox Signal 2009; [5] Ibrahim, I. M., et al., Life Sci 2019; [6] Ni, M., et al., FEBS Lett 2011).

Other names

HSPA5BiPBinding immunoglobulin protein78 kDa glucose-regulated proteinHeat shock protein family A member 5Endoplasmic reticulum lumenal Ca(2+)-binding protein grp78

Inhibition of chaperone activity, induction of apoptosis, blocking of cell surface signaling pathways (e.g., PI3K/Akt), and targeted delivery of cytotoxic agents via peptide-drug conjugates or antibody-dependent cellular cytotoxicity (ADCC).