Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 2009 Nov 10;106(45):19197-202. doi: 10.1073/pnas.0906593106. Epub 2009 Oct 26.
Impaired functioning of pancreatic beta cells is a key hallmark of type 2 diabetes. beta cell function is modulated by the actions of different classes of heterotrimeric G proteins. The functional consequences of activating specific beta cell G protein signaling pathways in vivo are not well understood at present, primarily due to the fact that beta cell G protein-coupled receptors (GPCRs) are also expressed by many other tissues. To circumvent these difficulties, we developed a chemical-genetic approach that allows for the conditional and selective activation of specific beta cell G proteins in intact animals. Specifically, we created two lines of transgenic mice each of which expressed a specific designer GPCR in beta cells only. Importantly, the two designer receptors differed in their G protein-coupling properties (G(q/11) versus G(s)). They were unable to bind endogenous ligand(s), but could be efficiently activated by an otherwise pharmacologically inert compound (clozapine-N-oxide), leading to the conditional activation of either beta cell G(q/11) or G(s) G proteins. Here we report the findings that conditional and selective activation of beta cell G(q/11) signaling in vivo leads to striking increases in both first- and second-phase insulin release, greatly improved glucose tolerance in obese, insulin-resistant mice, and elevated beta cell mass, associated with pathway-specific alterations in islet gene expression levels. Selective stimulation of beta cell G(s) triggered qualitatively similar in vivo metabolic effects. Thus, this developed chemical-genetic strategy represents a powerful approach to study G protein regulation of beta cell function in vivo.
胰岛β细胞功能障碍是 2 型糖尿病的一个关键特征。β细胞功能受不同种类的异三聚体 G 蛋白的作用调节。目前，对于体内激活特定β细胞 G 蛋白信号通路的功能后果知之甚少，主要是因为β细胞 G 蛋白偶联受体（GPCR）也在许多其他组织中表达。为了克服这些困难，我们开发了一种化学遗传学方法，允许在完整动物中条件性和选择性地激活特定的β细胞 G 蛋白。具体来说，我们创建了两条转基因小鼠系，每条系仅在β细胞中表达一种特定的设计型 GPCR。重要的是，这两种设计型受体在 G 蛋白偶联特性（G(q/11)与 G(s)）上有所不同。它们不能与内源性配体结合，但可以被一种原本药理学上无活性的化合物（氯氮平-N-氧化物）有效激活，导致β细胞 G(q/11)或 G(s)G 蛋白的条件性激活。在这里，我们报告了以下发现：体内条件性和选择性激活β细胞 G(q/11)信号通路可显著增加第一相和第二相胰岛素释放，极大改善肥胖、胰岛素抵抗小鼠的葡萄糖耐量，并增加β细胞质量，与胰岛基因表达水平的特定途径改变相关。选择性刺激β细胞 G(s)引发了类似的体内代谢效应。因此，这种开发的化学遗传学策略代表了一种在体内研究 G 蛋白调节β细胞功能的有力方法。
