PDF(Pubmed)
Abstract：
Serotonin or 5-hydroxytryptamine (5-HT) is a monoamine that plays a critical role in insulin secretion, energy metabolism, and mitochondrial biogenesis. However, the action of serotonin in insulin production and secretion by pancreatic β cells has not yet been elucidated. Here, we investigated how exogenous nanomolar serotonin concentrations regulate insulin synthesis and secretion in rat insulinoma INS-1E cells. Nanomolar serotonin concentrations (10 and 50 nM) significantly increased insulin protein expression above the constant levels in untreated control cells and decreased insulin protein levels in the media. The reductions in insulin protein levels in the media may be associated with ubiquitin-mediated protein degradation. The levels of membrane vesicle trafficking-related proteins including Rab5, Rab3A, syntaxin6, clathrin, and EEA1 proteins were significantly decreased by serotonin treatment compared to the untreated control cells, whereas the expressions of Rab27A, GOPC, and p-caveolin-1 proteins were significantly reduced by serotonin treatment. In this condition, serotonin receptors, Gαq-coupled 5-HT2b receptor (Htr2b), and ligand-gated ion channel receptor Htr3a were significantly decreased by serotonin treatment. To confirm the serotonylation of Rab3A and Rab27A during insulin secretion, we investigated the protein levels of Rab3A and Rab27A, in which transglutaminase 2 (TGase2) serotonylated Rab3A but not Rab27A. The increases in ERK phosphorylation levels were consistent with increases in the expression of p-Akt. Also, the expression level of the Bcl-2 protein was significantly increased by 50 and 100 nM serotonin treatment compared to the untreated control cells, whereas the levels of Cu/Zn-SOD and Mn-SOD proteins decreased. These results indicate that nanomolar serotonin treatment regulates the insulin protein level but decreases this level in media through membrane vesicle trafficking-related proteins (Rab5, Rab3A, syntaxin6, clathrin, and EEA1), the Akt/ERK pathway, and Htr2b/Htr3a in INS-1E cells.
摘要：
5-羟色胺或5-羟色胺（5-HT）是一种在胰岛素分泌中起关键作用的单胺，能量代谢，和线粒体生物发生。然而,5-羟色胺在胰腺β细胞产生和分泌胰岛素中的作用尚未阐明。这里,我们研究了外源性纳摩尔血清素浓度如何调节大鼠胰岛素瘤INS-1E细胞的胰岛素合成和分泌。在未处理的对照细胞中,纳摩尔血清素浓度(10和50nM)显著增加胰岛素蛋白表达高于恒定水平,并降低培养基中的胰岛素蛋白水平。培养基中胰岛素蛋白质水平的降低可能与泛素介导的蛋白质降解有关。膜囊泡运输相关蛋白的水平，包括Rab5，Rab3A，语法6，网格蛋白，与未处理的对照细胞相比，5-羟色胺处理显著降低了EEA1蛋白，而Rab27A的表达，GOPC,和p-caveolin-1蛋白通过5-羟色胺治疗显着降低。在这种情况下,血清素受体，Gαq偶联的5-HT2b受体（Htr2b），5-羟色胺治疗可显著降低配体门控离子通道受体Htr3a。为了确认胰岛素分泌过程中Rab3A和Rab27A的血清素化，我们调查了Rab3A和Rab27A的蛋白质水平，其中转谷氨酰胺酶2(TGase2)血清素化Rab3A而不是Rab27A。ERK磷酸化水平的增加与p-Akt表达的增加一致。此外，与未处理的对照细胞相比，Bcl-2蛋白的表达水平显着增加了50和100nM血清素处理，而Cu/Zn-SOD和Mn-SOD蛋白水平降低。这些结果表明，纳摩尔5-羟色胺治疗调节胰岛素蛋白水平，但通过膜囊泡运输相关蛋白（Rab5，Rab3A，语法6，网格蛋白，和EEA1)，Akt/ERK通路，和INS-1E细胞中的Htr2b/Htr3a。
