title: Cell surface targeting of the Melanocortin 5 Receptor (MC5R) requires serine-rich terminal motifs.
abstract: The Melanocortin 5 Receptor (MC5R) is a cell surface receptor that belongs to the class of G-protein coupled receptors (GPCRs), which comprises an intracellular carboxylic domain, seven transmembrane helices and an extracellular amino terminal. Over the last few years, MC5R has been implicated in the regulation of lipid metabolism in exocrine glands, muscle and even in adipose tissue and its function is quite dependent on its correct cell membrane targeting. In this context, the purpose of this work was to study the role of MC5R N-terminus in the receptor trafficking from the endoplasmic reticulum (ER) through the Golgi complex to the plasma membrane. Analysis of N-terminal deleted forms of MC5R revealed that the first 21 amino acids contain the information responsible for the receptor cell surface expression and the removal of further amino acids interfere with the receptor synthesis. In this setting, several mutant forms of the receptor were created by site directed mutagenesis of the MC5R first 21 amino acids and their presence at the plasma membrane was assessed. We have found that two small motifs, constituted by residues Ser4/Ser5 and Ser17/Glu18, are clearly involved in the correct targeting of MC5R to the cell surface. Fluorescence microscopy analysis has revealed that MC5R constructs with mutations in those residues are mainly retained at the ER/Golgi complex. Furthermore, the homodimerization ability of the receptor is maintained in these mutant forms, suggesting that other mechanisms are involved in the regulation of the anterograde transport of MC5R by those N-terminal domains.
authors.affiliation: Departamento de Biomedicina-Unidade de Biologia Experimental, Faculdade de Medicina da Universidade do Porto, Porto, Portugal; I3S - Instituto de Investigação e Inovação em Saúde, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
authors.forename: A R
authors.initials: AR
authors.lastname: Rodrigues
authors.affiliation: I3S - Instituto de Investigação e Inovação em Saúde, IPATIMUP, Universidade do Porto, Porto, Portugal.
authors.forename: D
authors.initials: D
authors.lastname: Sousa
authors.affiliation: Departamento de Biomedicina-Unidade de Biologia Experimental, Faculdade de Medicina da Universidade do Porto, Porto, Portugal; I3S - Instituto de Investigação e Inovação em Saúde, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
authors.forename: H
authors.initials: H
authors.lastname: Almeida
authors.affiliation: Departamento de Biomedicina-Unidade de Biologia Experimental, Faculdade de Medicina da Universidade do Porto, Porto, Portugal; I3S - Instituto de Investigação e Inovação em Saúde, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal; Faculdade de Ciências da Nutrição e Alimentação, Universidade do Porto, Porto, Portugal. Electronic address: agouveia@med.up.pt.
authors.forename: A M
authors.initials: AM
authors.lastname: Gouveia
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D000072417:Protein Domains; D055503:Protein Multimerization; D021382:Protein Sorting Signals; D021381:Protein Transport; D044101:Receptors, Melanocortin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000737:chemistry / Q000235:genetics
chemical_list: D021382:Protein Sorting Signals; D044101:Receptors, Melanocortin; C086971:melanocortin 5 receptor; D012694:Serine
keywords: Anterograde transport; GPCR; Intracellular trafficking; Melanocortin 5 Receptor; N-terminus