title: Melanopsins: Localization and Phototransduction in Xenopus laevis Melanophores.
abstract: Xenopus laevis melanophores express two melanopsins, Opn4x and Opn4m. We identified Opn4x immunoreactivity throughout the melanophore cytoplasm and in the cell membrane. The strongest immunopositivity for Opn4m was observed in the nuclear region, and no labeling was seen in the cell membrane. This immunodistribution suggests Opn4x as the functional photopigment. In X. laevis melanophores, light triggers pigment dispersion and clock gene induction at blue wavelength, which maximally activates melanopsins. Although light stimulation activates phospholipase C and increases intracellular calcium and cGMP, this nucleotide does not participate in photo-induced melanin dispersion. Nevertheless, the guanylyl cyclase activator YC-1 stimulates Per1 expression, similar to blue light pulse, and the use of pharmacological inhibitors indicates the participation of the phosphoinositide cascade. Since cAMP levels does not change after blue light stimulation, the cAMP/PKA pathway most probably is not involved in blue light induction of Per in X. laevis melanophores. Given the localization of melanopsins and our pharmacological data, the light-induced clock gene expression seems to be mediated by Opn4x through phosphoinositide cascade and rise in cGMP, thus leading to the reset of the biological clock in our model.
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Maria Nathália
authors.initials: MN
authors.lastname: Moraes
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Bruno C
authors.initials: BC
authors.lastname: Ramos
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.|Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Maristela O
authors.initials: MO
authors.lastname: Poletini
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Ana Maria L
authors.initials: AM
authors.lastname: Castrucci
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D008027:Light; D055537:Light Signal Transduction; D008547:Melanophores / Q000378:metabolism*; D008969:Molecular Sequence Data; D017299:Rod Opsins / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism*; D000099210:Melanopsin
chemical_list: D017299:Rod Opsins; D000099210:Melanopsin