Abstract
We have investigated at the single-cell level how the human LH receptor mediates a dose-responsive increase in intracellular free calcium-ion concentrations ([Ca2+]i). In human embryonic kidney cells (293 cells) stably transfected with the full-length human LH receptor cDNA. Intact dimeric LH, but not LH β- or α-subunits, evoked specific [Ca2+]i signals. High-resolution fluorescence (fura-2) video-microscopy demonstrated cell-to-cell variability in [Ca2+]i signaling responses in individual cells, viz., an all-or-none spike (9%), spike-and-plateau (25%), or plateau (52%) types of temporal signal. Oscillatory [Ca2+]i responses were observed in 12–14% of LH-stimulated cells unrelated to LH concentration. The LH dose-response originated by higher concentrations of LH recruiting more individually responding cells (rather than altering [Ca2+]i signal amplitude), and eliciting a [Ca2+]i rise more rapidly, i.e., at reduced latency. Cobalt did not abolish the LH-stimulated [Ca2+]i spike-and-lateau response, but decreased the percentage of cells with a plateau pattern. Quench experiments demonstrated influx of Mn2+ following the [Ca2+]i spike, thus directly documenting divalent cation inflow during the plateau phase. Adenylyl-cyclase activation with forskolin or treatment with a cAMP analog failed to elicit the biphasic [Ca2+]i resoonse, and pertussis toxin (PTX) did not alter LH-stimulated [Ca2+]i signaling. However, overnight preincubation with LH reduced the percentage of [Ca2+]i-responding cells following re-exposure to LH to 5.7% (vs 72% in control), suggesting LH-induced desensitization of the LH-receptor directed [Ca2+]i signal.
In summary, the present studies of human LH receptor signal transduction at the single-cell level show that increasing concentrations of LH achieve a dose-dependent intracellular Ca2+ signaling response by recruiting an increasing number of [Ca2+]i-responding cells, while concomitantly decreasing the temporal latency of the biphasic [Ca2+]i signal without altering the amplitude of its spike phase. Prolonged exposure to LH appears to desensitize the LH receptor-driven [Ca2+]i signal.
Similar content being viewed by others
References
Segaloff, D. L. and Ascoli, M. (1993).Endocr. Rev. 14, 324–347.
Davis, J. S., Weakland, L. L., Farese, R. V., and West, L. A. (1987).J. Biol. Chem. 262, 8515–8521.
Richards, J. S. (1980).Physiol. Rev. 60, 51–89.
Jia, X. C., Perlas, E., Su, J. G., Moran, F., Lasley, B. L., Ny, T., and Hsueh, A. J. (1993).Biol. Reprod. 49, 1310–1316.
Flores, J. A., Veldhuis, J. D., and Leong, D. A. (1990).Endocrinology 127, 3172–3179.
Flores, J. A., Veldhuis, J. D., and Leong, D. A. (1991).Mol. Cell. Endocrinol. 81, 1–10.
Veldhuis, J. D. and Hewlett, E. L. (1985).Biochem. Biophys. Res. Commun. 131, 1168–1174.
Berridge, M. J. (1993).Nature 361, 315–325.
Lakkakorpi, J. T. and Rajaniemi, H. J. (1994).Mol. Cell. Endocrinol. 99, 39–47.
Putney, J. W. and Bird, G. S. (1993).Endocr. Rev. 14, 610–631.
Miyazaki, S., Yuzak, M., Nakada, K., Shirakawa, H., Nakanishi, S., Nakade, S., and Mikoshiba, K. (1992).Science 257, 251–255.
Van Sande, J., Raspe, E., Perret, J., Lejeune, C., Maenhaut, C., Vassart, G., and Dumont, J. E. (1990).Mol. Cell. Endocrinol. 74, R1–6.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Sun, F., Berry, D.J., Leong, D.A. et al. Recruitment of individually (all-or-none) responding cells, rather than amplitude enhancement, is the single-cell mechanism subserving the dose-responsive activation of intracellular calcium second messenger signaling by the human lutinizing-hormone receptor. Endocr 7, 219–226 (1997). https://doi.org/10.1007/BF02778144
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02778144