tailieunhanh - Báo cáo khoa học: Presence of melanocortin (MC4) receptor in spiny dogfish suggests an ancient vertebrate origin of central melanocortin system

We report the cloning, expression, pharmacological char-acterization and tissue distribution of a melanocortin (MC) receptor gene in a shark, the spiny dogfish (Squalus acanth-ias) (Sac). Phylogenetic analysis showed that this receptor is anorthologof theMC4 subtype, sharing71%overall amino acid identity with the human (Hsa) MC4 receptor. When expressedandcharacterizedbyradioligandbindingassay for the natural MSH (melanocyte-stimulating hormone) pep-tides a-, b-, and c-MSH, the SacMC4 receptor showed pharmacological properties very similar to the HsaMC4 receptor. . | Eur. J. Biochem. 270 213-221 2003 FEBS 2003 doi Presence of melanocortin MC4 receptor in spiny dogfish suggests an ancient vertebrate origin of central melanocortin system Aneta Ringholm1 Janis Klovins1 Robert Fredriksson1 Natalia Poliakova1 Earl T. Larson1 Jyrki P. Kukkonen2 Dan Larhammar1 and Helgi B. Schioth1 Department of Neuroscience Division of 1 Pharmacology and Division of 2Physiology Uppsala University Uppsala Sweden We report the cloning expression pharmacological characterization and tissue distribution of a melanocortin MC receptor gene in a shark the spiny dogfish Squalus acanth-ias Sac . Phylogenetic analysis showed that this receptor is an ortholog of the MC4 subtype sharing 71 overall amino acid identity with the human Hsa MC4 receptor. When expressed and characterized by radioligand binding assay for the natural MSH melanocyte-stimulating hormone peptides a- b- and y-MSH the SacMC4 receptor showed pharmacological properties very similar to the HsaMC4 receptor. Stimulation of SacMC4 receptor transfected cells with a-MSH caused a dose-dependent increase in intracellular cAMP levels. The SacMC4 receptor has Ala in position 59 where all other cloned MC receptors have Glu. We confirmed that this was not due to individual polymorphism and subsequently mutated the residue back to Glu but the mutation did not affect the pharmacological properties of the receptor. SacMC4 receptor mRNA was detected by RT-PCR in the optic tectum hypothalamus brain stem telencephalon and olfactory bulb but not in cerebellum or in peripheral tissues. This study describes the first characterization of an MC receptor in a cartilaginous fish the most distant MC receptor gene cloned to date. Conservation of gene structure pharmacological properties and tissue distribution suggests that this receptor may have similar roles in sharks as in mammals and that these were established more than 450 million years ago. Keywords GPCR melanocortin .