Glucose Regulated Protein 94 (Grp94, gp96)

Glucose-regulated protein 94, also known as Grp94 or gp96, is an abundant resident endoplasmic reticulum (ER) lumenal stress protein which together with cytosolic Hsp90 belongs to the Hsp90 family of molecular chaperones. Grp94 and other resident soluble proteins of the ER such as members of the Ca(2+) binding protein subfamily (CaBP), CaBPI and CaBP2 as well as calreticulin, possess the COOH-terminal tetrapeptide Lys-Asp-Glu-Leu (KDEL) which is a sorting signal that is thought to lead to the retention of these proteins in the pre-Golgi compartments (1). Grp94 expression is upregulated by stress conditions such as lucose starvation and heat shock, which promote protein misfolding or unfolding (2). In addition to a homeostatic role in protein folding and assembly, Grp94 can function in the intracellular trafficking of peptides from the extracellular space to the MHC class I antigen processing pathway of antigen presentation cells (3,4). Grp94 and Hsp90 share high sequence identity and presumably identical adenosine nucleotide-dependent modes of regulation. Earlier data suggests that Hsp90 and Grp94 may differ in their nucleotide binding properties. The N-terminal domain of eukaryotic Hsp90 proteins contains a conserved adenosine nucleotide binding pocket which also serves as the inding site for the Hsp90 inhibitors geldanamycin and radicicol. However, the molecular basis for adenosine nucleotide-dependent regulation of Grp94remains to be established. Recent data has entified a ligand dependent regulation of Grp94 function and suggest a model whereby Grp94 function is regulated through a ligand-dependent conversion of Grp94 from an inactive to an active conformation (5, 6). Cellular Localization: Endoplasmic reticulum Applications: Suitable for use in Immunofluorescence, Western Blot and Immunoprecipitation. Other applications not tested. Recommended Dilution: Optimal dilutions to be determined by the researcher. Storage and Stability: May be stored at 4 degrees C for short-term only. For long-term storage and to avoid repeated freezing and thawing, aliquot Store at -20 degrees C. Aliquots are stable for at least 12 months at -20 degrees C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.