94 kDa glucose-regulated protein (GRP94) (GRP94)

The 94 kDa glucose-regulated protein (GRP94), also known as endoplasmin, is the endoplasmic reticulum (ER)-resident member of the heat shock protein 90 (HSP90) family (UniProt: P14625). It serves as a specialized molecular chaperone essential for the folding, assembly, and quality control of secreted and transmembrane proteins, including integrins, Toll-like receptors (TLRs), and insulin-like growth factors (PubMed: 23533130). GRP94 is frequently overexpressed in various malignancies, such as breast, lung, and colorectal cancers, where it supports the stability of oncogenic drivers and promotes tumor cell survival under ER stress (PubMed: 25103565). Beyond its role in cancer, GRP94 is involved in the innate immune response by facilitating the maturation of TLRs and acting as an adjuvant for cross-presentation of antigens (PubMed: 11907092). Therapeutic targeting of GRP94 primarily involves small-molecule inhibitors that bind to its N-terminal ATPase domain, thereby disrupting its chaperone cycle and inducing the degradation of its client proteins (PubMed: 24631464). While pan-HSP90 inhibitors have shown efficacy, they are often limited by systemic toxicities; consequently, current research focuses on developing isoform-selective GRP94 inhibitors to improve the therapeutic window for treating cancer and inflammatory disorders (PubMed: 28841314).

Other names

EndoplasminHeat shock protein 90 kDa beta member 1HSP90B1GP96Tumor rejection antigen 1TRA1ERp99

Inhibition of the N-terminal ATPase domain, which prevents the conformational cycle required for chaperone activity, leading to the degradation of client proteins via the ubiquitin-proteasome system.