A tetrapeptide within a receptor-binding region of human follicle-stimulating hormone beta-subunit, hFSH-beta-(34-37), regulates sodium-calcium exchange in Sertoli cells.
In a previous study, we showed that binding of FSH by cultured rat Sertoli cells significantly inhibited basal levels of Na+/Ca2+ exchange. Similar inhibition was observed when proteoliposomes enriched with bovine calf testis follicle-stimulating hormone (FSH) receptors were stimulated with FSH. In the present study, we screened a series of overlapping synthetic peptide amides, representing the entire primary structure of the beta-subunit of hFSH, for their effects on sodium-dependent calcium uptake (as 45Ca2+) by monolayer cultures of Sertoli cells from immature rats. hFSH-beta-(33-53), previously identified as a receptor binding region of hFSH-beta-subunit, significantly (P < 0.05) inhibited Na+/Ca2+ exchange. A tetrapeptide [TRDL, hFSH-beta-(34-37)] contained within this sequence, was observed to be equally as active as hFSH-beta-(33-53) at 200 microM, suggesting that the regulatory effect of hFSH-beta-(33-53) on sodium-dependent 45Ca2+ influx was due to residues 34-37. hFSH-beta-(81-95) also inhibited Na(+)-dependent calcium influx, although to a lesser extent than hFSH-beta-(33-53) or hFSH-beta-(34-37). Sodium-dependent 45Ca2+ entry into Sertoli cells was enhanced in a concentration-related manner when extracellular sodium was replaced by equimolar concentrations (up to 135 mM) of choline chloride. hFSH-beta-(34-37) significantly reduced basal uptake of 45Ca2+ in choline-containing buffer, but was without effect in buffer containing 135 mM NaCl.(ABSTRACT TRUNCATED AT 250 WORDS)
Grasso
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Department of Biochemistry and Molecular Biology, Albany Medical College, New York 12208.
Joseph
M P
MP
Reichert
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D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D037201:Follicle Stimulating Hormone, beta Subunit; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012708:Sertoli Cells / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D037201:Follicle Stimulating Hormone, beta Subunit; D008081:Liposomes; D010446:Peptide Fragments; D005640:Follicle Stimulating Hormone; D012964:Sodium; D002118:Calcium