| Association of the thyrotropin receptor with calnexin , calreticulin and BiP . ^^^ In this study , we investigated whether calnexin ( CNX ) , calreticulin ( CRT ) and BiP , three of the main molecular chaperones present in the endoplasmic reticulum , interact with the TSHR and what effects these interactions might have on the folding of the receptor . ^^^ The overexpression of calnexin and calreticulin in these cells stabilizes the receptor during the first hour after its synthesis , whereas the degradation of TSHR increased in a cell line overexpressing BiP and the quantity of TSHR able to acquire complex type oligosaccharides decreased . ^^^ These results show that calnexin , calreticulin and BiP all interact with TSHR and that the choice made between these two chaperone systems is crucial because each of them has distinct effects on the folding and stability of this receptor at the endoplasmic reticulum level . . ^^^ |