Grp94 is the endoplasmic reticulum (ER) paralog of heat shock protein (Hsp) 90. This chaperone/stress protein belongs to the protein family of glucose-regulated proteins (Grp), whose levels increase in mammalian cell cultures in the absence of glucose. Other ER stressors, such as calcium depletion, inhibition of glycosylation, and reducing agents, similarly affected Grp94 protein levels, making it one of the hallmarks of ER stress response (Lee 1987). Grp94 protein relative amount is increased also after exposure to low doses of endotoxin or curcumin (Vitadello et al. 2014a), to hypoxia or mild ischemia. The upregulation of Grp94 in several tumors explains the other widely used synonyms gp96 and TRA1 (Ansa-Addo et al. 2016).
The apparent Mr of Grp94 is around 94–100 kDa in most vertebrate species and is the...
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