title: hMRAPa increases αMSH-induced hMC1R and hMC3R functional coupling and hMC4R constitutive activity.
abstract: Human melanocortin 2 receptor accessory protein (hMRAPa) is hypothesised to have functions beyond promoting human melanocortin 2 receptor (hMC2R) functional expression. To understand these potential functions, we exogenously co-expressed hMRAPa-FLAG with each of the five hMCR subtypes in HEK293 cells and assessed hMCR subtype coupling to adenylyl cyclase. We also co-expressed each HA-hMCR subtype with hMRAPa-FLAG to investigate their subcellular localisation. hMRAPa-FLAG enhanced α-melanocyte stimulating hormone (α-MSH)-stimulated hMC1R and hMC3R but reduced NDP-α-MSH-stimulated hMC5R, maximum coupling to adenylyl cyclase. hMRAPa-FLAG specifically increased hMC4R constitutive coupling to adenylyl cyclase despite not co-localising with the HA-hMC4R in the cell membrane. hMRAPa-FLAG co-localised with HA-hMC1R or HA-hMC3R in the perinuclear region, in cytoplasmic vesicles and at the plasma membrane, while it co-localised with HA-hMC2R, HA-hMC4R and HA-hMC5R predominantly in cytoplasmic vesicles. These diverse effects of hMRAPa indicate that hMRAPa could be an important modulator of the central and peripheral melanocortin systems if hMRAPa and any hMCR subtype co-express in the same cell.
authors.affiliation: Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand.
authors.forename: Emma I
authors.initials: EI
authors.lastname: Kay
authors.forename: Rikus
authors.initials: R
authors.lastname: Botha
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Montgomery
authors.forename: Kathleen G
authors.initials: KG
authors.lastname: Mountjoy
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D058286:Calcitonin Receptor-Like Protein / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D015870:Gene Expression; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport; D044102:Receptor, Melanocortin, Type 1 / Q000235:genetics / Q000378:metabolism*; D044104:Receptor, Melanocortin, Type 3 / Q000378:metabolism*; D044105:Receptor, Melanocortin, Type 4 / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D014162:Transfection; D000521:alpha-MSH / Q000494:pharmacology*
chemical_list: D058286:Calcitonin Receptor-Like Protein; C458099:MRAP protein, human; D008565:Membrane Proteins; D044102:Receptor, Melanocortin, Type 1; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D011993:Recombinant Fusion Proteins; D000521:alpha-MSH; D000262:Adenylyl Cyclases; D015740:Calcitonin Gene-Related Peptide