HSP90 proteins are highly conserved molecular chaperones that have key roles in signal transduction, protein folding, protein degradation, and morphologic evolution. Glucose-regulated protein 94 (GRP94) is one of the most abundant endoplasmic reticulum (ER) resident proteins and is the ER counterpart of the cytoplasmic heat shock protein 90 (HSP90). GRP94 exists as homodimers containing an N-terminal ATP-binding domain, peptide-binding domain, and C-terminal dimerization domain. GRP94, a component of the GRP78 chaperone system in protein processing, has pro-survival properties with implicated function in cancer progression and autoimmune disease. In mouse tumor models, GRP94 derived from cancer cells also induces anti-tumor immune responses. One reason for this tumor immunogenicity is that GRP94 binds to the peptides from proteins in cancer cells and can therefore present these peptides as tumor antigens. Loss of function studies on GRP94 showed that it is required for embryonic development, regulation of toll-like receptors, and innate immunity of macrophages. Furthermore, GRP94 expression is strikingly high in dendritic cells, smooth muscle, and lung bronchial epithelium and has been shown to induce maturation of dendritic cells.

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