Endocrinology, Vol 131, 2622-2628, Copyright © 1992 by Endocrine Society

ARTICLES

Correlation of follicle-stimulating hormone (FSH)-receptor complex internalization with the sustained phase of FSH-induced calcium uptake by cultured rat Sertoli cells

P Grasso, TA Santa-Coloma and LE Reichert Jr
Department of Biochemistry and Molecular Biology, Albany Medical College, New York 12208.

We have previously reported that synthetic peptide amides corresponding to regions of the beta-subunit of human FSH [hFSH-beta-(1-15) and hFSH- beta-(51-65)] have the ability to bind calcium and to facilitate its entry into liposomes. In the present study, we have examined the ability of synthetic peptides corresponding to the entire primary structure of hFSH-beta-subunit, to induce calcium influx in cultured rat Sertoli cells. Calcium (as 45Ca2+) uptake in response to 50 microM hFSH-beta-(1-15), hFSH-beta-(21-35), or hFSH-beta-(51-65) peptide amides was 2.5-, 2.4-, and 2.0-fold higher, respectively, than basal uptake. Pretreatment of Sertoli cells for 5 min with phenylarsine oxide (PAO, 80 microM), an inhibitor of receptor-mediated endocytosis, significantly (P < 0.05) reduced 45Ca2+ influx in response to hFSH-beta- (1-15), hFSH-beta-(21-35), and hFSH-beta-(51-65). A delay of 20 min was required, however, before the inhibitory effect of PAO on 45Ca2+ uptake was observed. Specific binding of [125I] hFSH to receptor at 4 C was unaffected by PAO. After 2 h at 37 C, however, approximately 1.6-fold more [125I]hFSH specifically bound at 4 C could be dissociated from the cell surfaces of PAO-pretreated Sertoli cell monolayers, compared to untreated monolayers. This result is consistent with an inhibitory effect of PAO on FSH receptor internalization. Chloroquine (at 100 microM), a lysosomotropic agent known to block FSH degradation, also significantly (P < 0.05) inhibited FSH-induced 45Ca2+ uptake. Extending our earlier studies, these results suggest that the sustained (> 20 min) phase of FSH-induced calcium uptake, also seen in response to synthetic hFSH-beta-(1-15), hFSH-beta-(21-35), and hFSH-beta-(51-65) peptide amides, may occur as a consequence of FSH-receptor complex internalization and FSH degradation. Vesicular uptake of extracellular calcium, which accompanies internalization of FSH-receptor complexes, and release of channel-forming peptides by lysosomal hydrolysis of FSH suggests a novel mechanism whereby FSH increases intracellular calcium levels in Sertoli cells.

This article has been cited by other articles:

				T.-H. Lai, Y.-F. Lin, F.-C. Wu, and Y.-H. Tsai Follicle-Stimulating Hormone-Induced G{alpha}h/Phospholipase C-{delta}1 Signaling Mediating a Noncapacitative Ca2+ Influx through T-Type Ca2+ Channels in Rat Sertoli Cells Endocrinology, March 1, 2008; 149(3): 1031 - 1037. [Abstract] [Full Text] [PDF]

				Y.-F. Lin, M.-J. Tseng, H.-L. Hsu, Y.-W. Wu, Y.-H. Lee, and Y.-H. Tsai A Novel Follicle-Stimulating Hormone-Induced G{alpha}h/Phospholipase C-{delta}1 Signaling Pathway Mediating Rat Sertoli Cell Ca2+-Influx Mol. Endocrinol., October 1, 2006; 20(10): 2514 - 2527. [Abstract] [Full Text] [PDF]

				K. A. Young, G. F. Ball, and R. J. Nelson Photoperiod-Induced Testicular Apoptosis in European Starlings (Sturnus vulgaris) Biol Reprod, February 1, 2001; 64(2): 706 - 713. [Abstract] [Full Text]

				M. Simoni, J. Gromoll, and E. Nieschlag The Follicle-Stimulating Hormone Receptor: Biochemistry, Molecular Biology, Physiology, and Pathophysiology Endocr. Rev., December 1, 1997; 18(6): 739 - 773. [Abstract] [Full Text]