The pseudokinase tribbles homolog 3 interacts with ATF4 to negatively regulate insulin exocytosis in human and mouse β cells
The pseudokinase tribbles homolog 3 interacts with ATF4 to negatively regulate insulin exocytosis in human and mouse β cells
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DOI：
10.1172/jci36849
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发表时间：
2010-08-01
影响因子：
15.9
通讯作者：
Kulkarni, Rohit N.
中科院分区：
文献类型：
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作者：
Liew, Chong Wee;Bochenski, Jacek;Kulkarni, Rohit N.
胰岛素分泌不足和胰腺β细胞质量减少是2型糖尿病（T2DM）的标志。在这里，我们证实了先前发现的假激酶编码基因tribbles 3 （TRB3）外显子2的多态性（rs2295490/Q84R）与2个欧洲混血人群中T2DM风险增加有关。携带84R等位基因的人血浆c肽水平显著降低，c肽是胰岛素原加工成胰岛素的产物，这表明TRB3在β细胞功能中起作用。TRB3 84R在小鼠β细胞、人胰岛细胞和小鼠β细胞系MIN6中的过表达显示胰岛素分泌减少，并与电子显微镜观察到的停靠胰岛素颗粒明显减少有关。相反，在MIN6细胞中敲低TRB3可以恢复胰岛素分泌和胞吐基因的表达。在MIN6细胞中的进一步分析表明，TRB3与转录因子ATF4相互作用，该复合物作为cAMP反应元件结合（CREB）转录因子的竞争性抑制剂，调控关键的胞吐基因。此外，84R TRB3变体比野生型TRB3表现出更高的蛋白质稳定性，并增加了与Akt的结合亲和力。在β细胞中过表达TRB3 84R的小鼠显示β细胞质量下降，增殖减少和凋亡率增加。这些数据将人类TRB3的错义多态性与胰岛素胞吐功能受损联系起来，从而增加了患T2DM的风险。
Insufficient insulin secretion and reduced pancreatic beta cell mass are hallmarks of type 2 diabetes (T2DM). Here, we confirm that a previously identified polymorphism (rs2295490/Q84R) in exon 2 of the pseudokinase-encoding gene tribbles 3 (TRB3) is associated with an increased risk for T2DM in 2 populations of people of mixed European descent. Carriers of the 84R allele had substantially reduced plasma levels of C-peptide, the product of proinsulin processing to insulin, suggesting a role for TRB3 in beta cell function. Overexpression of TRB3 84R in mouse beta cells, human islet cells, and the murine beta cell line MIN6 revealed reduced insulin exocytosis, associated with a marked reduction in docked insulin granules visualized by electron microscopy. Conversely, knockdown of TRB3 in MIN6 cells restored insulin secretion and expression of exocytosis genes. Further analysis in MIN6 cells demonstrated that TRB3 interacted with the transcription factor ATF4 and that this complex acted as a competitive inhibitor of cAMP response element-binding (CREB) transcription factor in the regulation of key exocytosis genes. In addition, the 84R TRB3 variant exhibited greater protein stability than wild-type TRB3 and increased binding affinity to Akt. Mice overexpressing TRB3 84R in beta cells displayed decreased beta cell mass, associated with reduced proliferation and enhanced apoptosis rates. These data link a missense polymorphism in human TRB3 to impaired insulin exocytosis and thus increased risk for T2DM.