Calreticulin is involved in regulation of intracellular Ca2+ homoeostasis and ER Ca2+ capacity. It constitutes together with calnexin and ERp57 the 'calreticulin/calnexin cycle' that is responsible for folding and quality control of newly synthesized glycoproteins. Calreticulin has been implicated to play a role in many biological systems, including functions inside and outside the ER, indicating that the protein is a multi-process molecule. Recently, Calreticulin was shown to enhance the merger of macrophages and tumor cells, increasing phagocytosis.