Calreticulin is a calcium-dependent ER chaperone, involved in protein folding, maturation, and cellular localization. Calreticulin is a highly conserved 48 kDa protein encoded by the CALR gene. Calreticulin and its homolog calnexin regulate the folding and degradation of newly synthesized glycoproteins as they are translocated into the ER (1). Misfolded proteins recognized by calreticulin are targeted to the ER-associated degradation (ERAD) pathway. Within the ER, calreticulin also plays an important role in calcium homeostasis.