Endogenous melanin-concentrating hormone receptor SLC-1 in human melanoma SK-MEL-37 cells

Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide that reg ulates several physiological functions. The orphan G protein-coupled recept ors SLC-1 and MCHR2 were recently found to bind MCH with high affinity. We show here that the human melanoma cell line SK-MEL-37 expresses SLC-1 mRNA but not MCHR2 by RT-PCR analysis and immunofluorescence studies. Using Chin ese hamster ovary cells and 293 cells overexpressing SLC-1 by cDNA transfec tion, it was shown that SLC-1 coupled to both G alpha (i)/G alpha (o) and G alpha (q) proteins. In SK-MEL-37 cells, MCH inhibited forskolin-stimulated cyclic AMP accumulation and induced mitogen-activated protein kinase (MAPK ) in a pertussis toxin- (PTX) -sensitive manner. The MAPK activity leads to the production of phosphorylated forms of p42/p44 MAPK. However, an increa se in the intracellular free Ca2+ concentration was not elicited by MCH in SK-MEL-37 cells. These results show that SLC-1 is coupled only to PTX-sensi tive Gai/Gao in SK-MEL-37 cells. This study provides for the first time a s kin-derived cellular model to analyze the molecular mechanism of the MCH si gnaling pathway. (C) 2001 Academic Press.