A follicle-stimulating hormone receptor ecto-domain epitope that is a target for receptor immunoneutralization yet does not affect ligand contact and activation.
The follicle-stimulating hormone receptor (FSHR) large extracellular domain suggests that interaction of ligand with receptor is likely to be complex. Residues 265-296 of the FSHR are part of a sequence primarily nonhomologous with other glycoprotein hormone receptors. A reasonable hypothesis is that this sequence of the FSHR plays a role in binding FSH. Flow cytometry studies of this region revealed that antibody X179 against peptide R265-S296 binds to human FSHR expressed by CHO cells and can be competed against by preincubating the cells with hFSH. These results suggested that the region corresponding to residues 265-296 in the extracellular domain of the FSHR is involved in binding to hormone. To test this hypothesis 10 scanning alanine mutants of rFSHR at the 265-296 epitope were generated, and the binding characteristics of these mutants were studied. Their affinity constants for 125I-hFSH did not deviate greatly from that of wild-type FSHR, in which some mutants exhibited an approximately two- to threefold reduction in Ka compared to wild-type receptor, and no mutation abolished signal transduction. These results lead to rejection of the hypothesis that this region contains residues critical for conveying hormone specificity and receptor-dependent hormone action.
Liu
X
X
Department of Biomedical Sciences, School of Public Health, University of Albany, NY 12208, USA.
Butterstein
G M
GM
Lindau-Shepard
B
B
Brumberg
H A
HA
Dia
J A
JA
D000409:Alanine; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D005434:Flow Cytometry; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D007106:Immune Sera / Q000378:metabolism / Q000494:pharmacology; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011869:Radioligand Assay; D011962:Receptors, FSH / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D018411:Spodoptera / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection
D000939:Epitopes; D007106:Immune Sera; D011962:Receptors, FSH; D011994:Recombinant Proteins; D005640:Follicle Stimulating Hormone; D000409:Alanine