Unexpectedly, when 125I-hFSH bound to hFSHR-D550A or hFSHR-D550G, intracellular accumulation of radiolabeled FSH was observed. Maximal cAMP production of both hFSHR-D550A as well as the naturally occurring mutation hFSHR-D550G was diminished, but constitutive activity was not observed. Western blot analyses showed lower levels of mature hFSHR-D550A.
The hFSHR-D550A binds hormone similarly to WT-hFSHR when expressed in HEK293T cells. Because CK2 has been reported to play a role in trafficking of some receptors, the potential roles for CK2 and D550 in FSHR function were evaluated by generating a D550A mutation in the hFSHR. This residue is contained in a protein kinase-CK2 consensus site present in human FSHR (hFSHR) intracellular loop 3 (i元). A naturally occurring mutation in follicle-stimulating hormone receptor (FSHR) gene has been reported: an amino acid change to glycine occurs at a conserved aspartic acid 550 (D550, D567, D6.30 567).
