Protein disulfide isomerase chaperone ERP-57 decreases plasma membrane expression of the human GnRH receptor.
Retention of misfolded proteins by the endoplasmic reticulum (ER) is a quality control mechanism involving the participation of endogenous chaperones such as calnexin (CANX). CANX interacts with and restricts plasma membrane expression (PME) of the gonadotropin releasing hormone receptor (GnRHR), a G protein-coupled receptor. CANX also interacts with ERP-57 a thiol oxidoreductase chaperone present in the ER. CANX along with ERP-57 promotes the formation of disulfide bond bridges in nascent proteins. The human GnRH receptor (hGnRHR) is stabilized by two disulfide bond bridges (C(14)-C(200) and C(114)-C(196)), that, when broken, lead to a decrease in receptor expression at the plasma membrane. To determine if the presence of chaperones CANX and ERP-57 exerts an influence over membrane routing and second messenger activation, we assessed the effect of various mutants including those with broken disulfide bridges (Cys --> Ala) along with the hGnRHR. The effect of chaperones on mutants was insignificant, whereas the over expression of ERP-57 led to an hGnRHR retention. This effect was further enhanced by cotransfection with cDNA for CANX showing receptor retention by ERP-57 augmented by CANX, suggesting utilization of these chaperones for quality control of the GnRHR.
Ayala Yáñez
Rodrigo
R
Oregon National Primate Research Center, Beaverton, 97006, USA.
Conn
P Michael
PM
D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D037281:Calnexin / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D018832:Molecular Chaperones / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D019704:Protein Disulfide-Isomerases / Q000378:metabolism*; D017510:Protein Folding; D011966:Receptors, LHRH / Q000378:metabolism*
D018832:Molecular Chaperones; D011966:Receptors, LHRH; D037281:Calnexin; D019704:Protein Disulfide-Isomerases; C085868:PDIA3 protein, human