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Sci. Signal., 8 October 2013
Vol. 6, Issue 296, p. ra89
[DOI: 10.1126/scisignal.2004302]


Heteromeric MT1/MT2 Melatonin Receptors Modulate Photoreceptor Function

Kenkichi Baba1*, Abla Benleulmi-Chaachoua2,3,4*, Anne-Sophie Journé2,3,4, Maud Kamal2,3,4, Jean-Luc Guillaume2,3,4, Sébastien Dussaud5, Florence Gbahou2,3,4, Katia Yettou2,3,4, Cuimei Liu1, Susana Contreras-Alcantara1, Ralf Jockers2,3,4{dagger}{ddagger}, and Gianluca Tosini1{dagger}{ddagger}

1 Neuroscience Institute and Department of Pharmacology and Toxicology, Morehouse School of Medicine, Atlanta, GA 30310, USA.
2 INSERM, U1016, Institut Cochin, Paris, France.
3 CNRS, UMR 8104, Paris, France.
4 Université Paris Descartes, Paris, France.
5 Centre d’Expérimentation Fonctionnelle, Hôpital Pitié-Salpêtrière Medical Faculty, Université Pierre et Marie Curie, FR-75013 Paris, France.

* Co-first authors.

{dagger} Co-last authors.

Abstract: The formation of G protein (heterotrimeric guanine nucleotide–binding protein)–coupled receptor (GPCR) heteromers enables signaling diversification and holds great promise for improved drug selectivity. Most studies of these oligomerization events have been conducted in heterologous expression systems, and in vivo validation is lacking in most cases, thus questioning the physiological significance of GPCR heteromerization. The melatonin receptors MT1 and MT2 exist as homomers and heteromers when expressed in cultured cells. We showed that melatonin MT1/MT2 heteromers mediated the effect of melatonin on the light sensitivity of rod photoreceptors in mice. This effect of melatonin involved activation of the heteromer-specific phospholipase C and protein kinase C (PLC/PKC) pathway and was abolished in MT1–/– or MT2–/– mice, as well as in mice overexpressing a nonfunctional MT2 mutant that interfered with the formation of functional MT1/MT2 heteromers in photoreceptor cells. Not only does this study establish an essential role of melatonin receptor heteromers in retinal function, it also provides in vivo support for the physiological importance of GPCR heteromerization. Thus, the MT1/MT2 heteromer complex may provide a specific pharmacological target to improve photoreceptor function.

{ddagger} Corresponding author. E-mail: gtosini{at} (G.T.); ralf.jockers{at} (R.J.)

Citation: K. Baba, A. Benleulmi-Chaachoua, A.-S. Journé, M. Kamal, J.-L. Guillaume, S. Dussaud, F. Gbahou, K. Yettou, C. Liu, S. Contreras-Alcantara, R. Jockers, G. Tosini, Heteromeric MT1/MT2 Melatonin Receptors Modulate Photoreceptor Function. Sci. Signal. 6, ra89 (2013).

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G Protein-Coupled Receptor Oligomerization Revisited: Functional and Pharmacological Perspectives.
S. Ferre, V. Casado, L. A. Devi, M. Filizola, R. Jockers, M. J. Lohse, G. Milligan, J.-P. Pin, and X. Guitart (2014)
Pharmacol. Rev. 66, 413-434
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