Expression of the human follicle-stimulating hormone receptor in the baculovirus system

Human follitropin receptor (hFSHR) cDNA was inserted into the genome of Autographa californica nuclear polyhedrosis virus under the control of the polyhedrin promoter. Spodoptera frugiperda (Sf9) insect cells expressed the hFSHR at the membrane level, 2-3 days after infection. Ligand binding analysis demonstrated saturable, high-affinity binding of 125I-labeled recombinant hFSH (Kd = 0.17 nM) as well as binding specificity for both human and equine FSH. Interestingly, a highly purified preparation of equine choriogonadotropin was found to compete with the binding of 125I-rhFSH. Finally, Western-blot analysis, using a monoclonal antipeptide antibody directed to the 178-206 region of the hFSHR, revealed two bands migrating at M(r) 77 and 130 kDa.