Calnexin (CNX), an abundant ~90 Kda molecular
chaperone, is a unglycosylated resident ER transmembrane protein.
In mammalian cells, calnexin, together with calreticulin (CRT),
plays a key role in glycoprotein folding and its control within
the ER, by interacting with folding intermediates via their monoglucosylated
glycans. Calnexin associates with newly synthesized monomeric glycoproteins
and only recognizes glycoproteins when they are incompletely folded.
Calnexin associates with numerous oligomeric protein complexes
within the ER, including integrins, major histocompatibility class
I and class II molecules, the antigen receptors expressed on T
and B lymphocytes, human thyroperoxidase (hTPO), and acetylcholine
receptor . Recent data also suggest that calnexin might be responsible
for the prolonged retention of pro-6 integrin within ER compartment.
Furthermore, calnexin has been demonstrated to function as a bonafide
molecular chaperone capable of interacting with polypeptide segments
of folding glycoproteins.
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