HSPA5 and infection: In the context of mock infection or HCV infection, BiP, a chaperone located in the lumen of the ER, and GAPDH, a cytosolic protein, were predominantly fractionated into fractions 8 and 9 and fractions 15 to 22, representing the ER/endosome and soluble/aggregated protein fractions, respectively (Fig. 6A).