TY - JOUR
T1 - Rescue of misrouted GnRHR mutants reveals its constitutive activity
AU - Janovick, Jo Ann
AU - Pogozheva, Irina D.
AU - Mosberg, Henry I.
AU - Cornea, Anda
AU - Michael Conn, P.
PY - 2012/7
Y1 - 2012/7
N2 - G protein-coupled receptors (GPCR) play central roles in almost all physiological functions, and mutations in GPCR are responsible for over 30 hereditary diseases associated with loss or gain of receptor function. Gain of function mutants are frequently described as having constitutive activity (CA), that is, they activate effectors in the absence of agonist occupancy. Although many GPCR have mutants with CA, the GnRH receptor (GnRHR) was not, until 2010, associated with any CA mutants. The explanation for the failure to observe CA appears to be that the quality control system of the cell recognizes CA mutants of GnRHR as misfolded and retains them in the endo-plasmic reticulum. In the present study, we identified several human (h)GnRHR mutants with substitutions in transmembrane helix 6 (F272K, F272Q, Y284F, C279A, and C279S) that demonstrate varying levels of CA after being rescued by pharmacoperones from different chemical classes and/or deletionofresidue K191,a modification that increases traffickingtothe plasma membrane. The movement of the mutants from the endoplasmic reticulum (unrescued) to the plasma membrane (after rescue) is supported by confocal microscopy. Judging from the receptor-stimulated inositol phosphate production, mutants F272K and F272Q, after rescue, display the largest level of CA, an amount that is comparable with agonist-stimulated activation. Because mutations in other GPCR are, like the hGnRHR, scrutinized by the quality control system, this general approach may reveal CA in receptor mutants from other systems. A computer model of the hGnRHR and these mutants was used to evaluate the conformation associated with CA.
AB - G protein-coupled receptors (GPCR) play central roles in almost all physiological functions, and mutations in GPCR are responsible for over 30 hereditary diseases associated with loss or gain of receptor function. Gain of function mutants are frequently described as having constitutive activity (CA), that is, they activate effectors in the absence of agonist occupancy. Although many GPCR have mutants with CA, the GnRH receptor (GnRHR) was not, until 2010, associated with any CA mutants. The explanation for the failure to observe CA appears to be that the quality control system of the cell recognizes CA mutants of GnRHR as misfolded and retains them in the endo-plasmic reticulum. In the present study, we identified several human (h)GnRHR mutants with substitutions in transmembrane helix 6 (F272K, F272Q, Y284F, C279A, and C279S) that demonstrate varying levels of CA after being rescued by pharmacoperones from different chemical classes and/or deletionofresidue K191,a modification that increases traffickingtothe plasma membrane. The movement of the mutants from the endoplasmic reticulum (unrescued) to the plasma membrane (after rescue) is supported by confocal microscopy. Judging from the receptor-stimulated inositol phosphate production, mutants F272K and F272Q, after rescue, display the largest level of CA, an amount that is comparable with agonist-stimulated activation. Because mutations in other GPCR are, like the hGnRHR, scrutinized by the quality control system, this general approach may reveal CA in receptor mutants from other systems. A computer model of the hGnRHR and these mutants was used to evaluate the conformation associated with CA.
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U2 - 10.1210/me.2012-1089
DO - 10.1210/me.2012-1089
M3 - Article
C2 - 22595961
AN - SCOPUS:84863326309
SN - 0888-8809
VL - 26
SP - 1179
EP - 1188
JO - Molecular Endocrinology
JF - Molecular Endocrinology
IS - 7
ER -