Purification of a paracrine factor, P-Mod-S, produced by testicular peritubular cells that modulates Sertoli cell function.
A testicular paracrine factor, P-Mod-S, was purified from conditioned medium obtained from serum-free cultures of peritubular cells. Stimulation of testicular transferrin production by cultured Sertoli cells was utilized as a bio-assay for P-Mod-S. A bioactive protein with an apparent molecular weight of 50,000 under physiological conditions was isolated by high pressure size exclusion chromatography. P-Mod-S was found to have an affinity for heparin and bound to a heparin affinity column. Two forms of P-Mod-S were purified with reverse-phase chromatography. The less hydrophobic form was referred to as P-Mod-S (A) and is a 56,000 molecular weight protein. The more hydrophobic form was referred to as P-Mod-S (B) and is a 59,000 molecular weight protein. Purification of P-Mod-S (A) and P-Mod-S (B) from peritubular cell-radiolabeled secreted proteins revealed that both proteins contain radioactivity. This result demonstrates active synthesis and secretion of P-Mod-S by peritubular cells. Although the amino acid composition of the two proteins indicates distinct differences in the content of several amino acids, the relationship of P-Mod-S (A) and P-Mod-S (B) is unknown at present. A greater than 1000-fold increase in the specific activity of P-Mod-S was achieved with the purification procedure utilized. P-Mod-S can account for essentially all the bioactivity present in crude peritubular cell-secreted protein preparations. The effects of the two forms of P-Mod-S on both transferrin and androgen-binding protein production by Sertoli cells was examined. Purified forms of P-Mod-S were found to have a greater effect on Sertoli cell function than any individual regulatory agent previously known to influence the cell, including follicle-stimulating hormone. The significance of peritubular cell-Sertoli cell interactions mediated via P-Mod-S to spermatogenesis and testicular function is discussed, as well as insight provided into general mesenchymal-epithelial cell interactions.
Skinner
M K
MK
Department of Pharmacology, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232.
Fetterolf
P M
PM
Anthony
C T
CT
D000596:Amino Acids / Q000032:analysis; D000727:Androgen-Binding Protein / Q000378:metabolism; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005470:Fluorometry; D008297:Male; D008970:Molecular Weight; D051381:Rats; D012708:Sertoli Cells / Q000502:physiology*; D013091:Spermatogenesis; D013735:Testicular Hormones / Q000302:isolation & purification*; D013737:Testis / Q000166:cytology* / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism
D000596:Amino Acids; D000727:Androgen-Binding Protein; C054951:P-Mod-S paracrine factor; D013735:Testicular Hormones; D014168:Transferrin