Molecular Cloning and Functional Characterization of MCH2, a Novel Human MCH Receptor

Abstract

Melanin-concentrating hormone (MCH) is involved in the regulation of feeding and energy homeostasis. Recently, a 353-amino acid splice variant form of the human orphan receptor SLC-1 (1) (hereafter referred to as MCH 1 ) was identified as an MCH receptor. This report describes the cloning and functional characterization of a novel second human MCH receptor, which we designate MCH 2 , initially identified in a genomic survey sequence as being homologous to MCH 1 receptors. Using this sequence, a full-length cDNA was generated with an open reading frame of 1023 base pairs, encoding a polypeptide of 340 amino acids, with 38% identity to MCH 1 and with many of the structural features conserved in G protein-coupled receptors. This newly discovered receptor belongs to class 1 (rhodopsin-like) of the G protein-coupled receptor superfamily. HEK293 cells transfected with MCH 2 receptors responded to nanomolar concentrations of MCH with an increase in intracellular Ca 2؉ levels and increased cellular extrusion of protons. In addition, fluorescently labeled MCH bound with nanomolar affinity to these cells. The tissue localization of MCH 2 receptor mRNA, as determined by quantitative reverse transcription-polymerase chain reaction, was similar to that of MCH 1 in that both receptors are expressed predominantly in the brain. The discovery of a novel MCH receptor represents a new potential drug target and will allow the further elucidation of MCH-mediated responses. Melanin-concentrating hormone (MCH)1 is a cyclic neuropeptide that was first discovered in teleost fish, in which it acts as a skin color-regulating hormone (2). In rodents its tissue distribution in the perikarya of the lateral hypothalamus and the zona incerta suggests that MCH may be involved in a variety of behavioral responses (3). Similar tissue distributions have been reported in both bird (4) and monkey (5). Reports implicating MCH in the regulation of feeding behavior show that increased food intake occurs after direct administration of MCH into the brain (6) and that MCH is up-regulated after fasting and in obese leptin-deficient mice (7). There are also reports that suggest MCH may be involved in aggressive behavior, anxiety, and reproductive function (8, 9).Recently, several groups independently identified a 353-amino acid splice variant of the orphan G protein-coupled receptor (GPCR) SLC-1 (1) as an MCH receptor (10 -14). In view of the findings of the current study, we propose that this form of SLC-1 be hereafter referred to as MCH 1 . Southern blot and related studies have indicated the absence of additional MCH receptor subtypes that closely resemble MCH 1 at the DNA level (3, 10, 15). However, because degeneracy in receptor-ligand pairings throughout the GPCR superfamily is common, we reasoned that other MCH receptors with low homology to the MCH 1 receptor may exist. This suggestion is supported by reports of pharmacological differences between the MCH 1 receptor and MCH binding sites in various cell lines and tissues (10).Sequencing of the human...

Effects of a specific MCHR1 antagonist (GW803430) on energy budget and glucose metabolism in diet‐induced obese mice

“…MCH acts via two G protein-coupled receptors, MCHR1 and MCHR2 (2) expressed in humans, rhesus monkeys (Macaca mulatta), dogs (Canis familiaris), and ferrets (Mustela putorius furo) with similar distribution patterns (2)(3)(4). However, MCHR2 is not expressed in rodents.…”

Microinjections of melanin concentrating hormone into the nucleus tractus solitarius of the rat elicit depressor and bradycardic responses

“…The distribution of MCH-1 receptor in the rat brain and spinal cord (Hervieu et al, 2000) overlaps the areas exhibiting MCH immunoreactivity (Bittencourt and Elias, 1998). A second MCH receptor, called the MCH-2 receptor, has also been identified (Hill et al, 2001;Mori et al, 2001;Rodriguez et al, 2001;Sailer et al, 2001;Songzhu et al, 2001;Wang et al, 2001). Non-primate species, including the rat, do not possess a functional MCH-2 receptor .…”

Melanin-concentrating hormone 1 receptor-deficient mice are lean, hyperactive, and hyperphagic and have altered metabolism

“…Subsequently, a second high-affinity MCH receptor (MCH2R) with moderate amino acid identity to MCH1R was identified in humans (11)(12)(13)(14)(15). Both receptors are highly selective for MCH and are not activated by NEI, neuropeptide GE, or MCH-gene-overprinted-polypeptide (13,16,17); however, in vivo validation for these receptors is still lacking.…”