Calmegin

Calmegin is a protein that functions as a molecular chaperone within the endoplasmic reticulum (ER), primarily involved in the quality control of glycoproteins. Specifically, it plays a crucial role in ensuring the proper folding and assembly of major histocompatibility complex class I (MHC-I) molecules and other client proteins.

Calmegin is a calcium-binding protein homologous to calreticulin. It interacts with newly synthesized glycoproteins through N-linked glycans, preventing their aggregation and premature exit from the ER. This interaction is facilitated by its lectin-like activity, which recognizes specific carbohydrate structures.

The chaperone activity of calmegin is essential for the efficient presentation of antigens by MHC-I molecules, a key process in cell-mediated immunity. By promoting the proper folding and assembly of MHC-I heavy chains with beta-2 microglobulin and peptide antigens, calmegin ensures that these molecules are correctly transported to the cell surface where they can be recognized by cytotoxic T lymphocytes.

Disruptions in calmegin function or expression can lead to impaired MHC-I presentation and compromised immune responses. Research suggests that calmegin may also play a role in other cellular processes, including calcium homeostasis and signal transduction.