Abstract
The pituitary peptide hormone α-MSH plays a role in pigmentation and fetal development and as a neuropeptide it influences behaviour and learning. In order to study α-MSH at the molecular level we have introduced a method of photoaffinity labelling of MSH receptors on intact pigment cells with which the biological response of the labelled cells could be continuously monitored. When melanophores of skin of Anolis carolinensis or Xenopus laevis where irradiated with UV-light in the presence of photoreactive α-MSH containing the photolabel in position 1, 9, or 13, a long-lasting signal was generated inducing irreversible pigment dispersion. A number of control experiments proved that the effect was specific. Calcium was shown to be indispensable for hormone-receptor binding and for the transduction of the signal from the receptor to the adenylate cyclase. Catecholamines acting through an alpha-2 receptor could reversibly inhibit the longlasting response of Anolis melanophores. The Xenopus model was also used for studying receptor turnover and degradation in the presence and absence of calcium. These and other results showed that irreversible stimulation by covalent labelling of hormone receptors represents a useful approach for studying stimulus-response coupling in intact cells, particularly when there are only few cells available.
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Eberle, A., De Graan, P. & Girard, J. Photoaffinity labeling of MSH receptors on pigment cells. Pediatr Res 18, 1207 (1984). https://doi.org/10.1203/00006450-198411000-00037
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DOI: https://doi.org/10.1203/00006450-198411000-00037