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.
I3S - Instituto de Investigação e Inovação em Saúde, IPATIMUP, Universidade do Porto, Porto, Portugal.
Biochim Biophys Acta Mol Cell Res. 2017 Jul;1864(7):1217-1226. doi: 10.1016/j.bbamcr.2017.04.004. Epub 2017 Apr 8.
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.
黑素皮质素受体 5（MC5R）是一种细胞表面受体，属于 G 蛋白偶联受体（GPCR）家族，其包含细胞内羧酸结构域、七个跨膜螺旋和细胞外氨基末端。在过去的几年中，MC5R 已被牵连到外分泌腺、肌肉甚至脂肪组织的脂质代谢调节中，其功能相当依赖于其正确的细胞膜靶向。在这种情况下，这项工作的目的是研究 MC5R N 末端在受体从内质网（ER）通过高尔基体复合物到质膜的运输过程中的作用。对 MC5R 缺失 N 末端形式的分析表明，前 21 个氨基酸包含负责受体细胞表面表达的信息，而进一步去除氨基酸会干扰受体的合成。在这种情况下，通过对 MC5R 前 21 个氨基酸进行定点突变，创建了几种受体的突变形式，并评估了它们在质膜上的存在。我们发现，由残基 Ser4/Ser5 和 Ser17/Glu18 组成的两个小基序显然参与了 MC5R 到细胞表面的正确靶向。荧光显微镜分析表明，这些残基发生突变的 MC5R 构建体主要保留在 ER/Golgi 复合物中。此外，这些突变形式中的受体同源二聚化能力得以维持，这表明其他机制参与了那些 N 末端结构域对 MC5R 顺行转运的调节。
