ABSTRACT
In our previous study, we had identified a 9-mer peptide (FSHß (89-97)) derived from seat belt loop of human FSHß and demonstrated its ability to function as FSHR antagonist in vivo. Structure analysis revealed that the four central residues 91STDC94 within this peptide may not be critical for receptor binding. In the present study, 91STDC94 residues were substituted with alanine to generate ΔFSHß 89-97(91STDC94/AAAA) peptide. Analogous to the parent peptide, ΔFSHß 89-97(91STDC94/AAAA) peptide inhibited binding of iodinated FSH to rat FSHR and reduced FSH-induced cAMP production. The peptide could impede granulosa cell proliferation leading to reduction in FSH-mediated ovarian weight gain in immature female rats. In these rats, peptide administration further downregulated androgen receptor and estrogen receptor-alpha expression and upregulated estrogen receptor-beta expression. The results indicate that substitution of 91STDC94 with alanine did not significantly alter FSHR antagonist activity of FSHß (89-97) peptide implying that these residues are not critical for FSH-FSHR interaction and can be replaced with non-peptidic moieties for development of more potent peptidomimetics.
Subject(s)
Drug Design , Follicle Stimulating Hormone/pharmacology , Peptides/pharmacology , Peptidomimetics , Receptors, FSH/antagonists & inhibitors , Animals , Binding Sites/drug effects , Female , Follicle Stimulating Hormone/chemistry , Humans , Models, Molecular , Ovary/drug effects , Peptides/chemistryABSTRACT
FSH-FSHR interaction is critical for folliculogenesis, spermatogenesis and progression of several cancers. Therefore, FSHR is an attractive target for fertility regulation and cancer therapeutics. Based on homology and structural analysis of hFSH-FSHR(ECD) complex, a minimal continuous stretch within FSHß seat-belt loop (FSHß (89-97)) was identified to be crucial for FSHR interaction. The ability of FSHß (89-97) peptide to neutralize FSHR activity was evaluated by a panel of in vitro and in vivo experiments. The synthetic peptide significantly inhibited binding of [125I]-FSH to rat Fshr as well as FSH-induced cAMP production. In immature rats, FSHß (89-97) peptide administration reduced FSH-mediated increase in ovarian weight. The peptide inhibited transition of follicles from pre-antral to antral stage and hindered the cell cycle progression of granulosa cells beyond G0/G1 phase. In adult rats, administration of the peptide inhibited estradiol synthesis and significantly perturbed folliculogenesis.
