Fridell Yih-Woei C, Hoh Melissa, Kréneisz Orsolya, Hosier Suzanne, Chang Chengyi, Scantling Dane, Mulkey Daniel K, Helfand Stephen L
Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912, USA.
Aging (Albany NY). 2009 Jul 21;1(8):699-713. doi: 10.18632/aging.100067.
To understand the role of mitochondrial uncoupling protein (UCP) in regulating insulin signaling and glucose homeostasis, we created transgenicDrosophila lines with targeted UCP expression in insulin producing cells (IPCs). Increased UCP activity in IPCs results in decreased steady state Ca(2+) levels in IPCs as well as decreased PI3K activity and increased FoxO nuclear localization in periphery. This reduced systemic insulin signaling is accompanied by a mild hyperglycemia and extended life span. To test the hypothesis that ATP-sensitive potassium (K(ATP)) channels may link changes in metabolic activity (e.g., glucose mediated ATP production or UCP-mediated ATP reduction) with insulin secretion, we characterized the effects of glucose and a specific K(ATP) channel blocker, glibenclamide on membrane potential in adult IPCs. Exposure to glucose depolarizes membrane potential of IPCs and this effect is mimicked with glibenclamide, suggesting that K(ATP) channels contribute to the mechanism whereby IPCs sense changes in circulating sugar. Further, as demonstrated in mammalian beta-pancreatic cells, high glucose initiates a robust Ca(2+) influx in adult IPCs. The presence of functional K(ATP) channels in adult IPCs is further substantiated by in situ hybridization detecting the transcript for the sulfonylurea receptor (Sur) subunit of the K(ATP) channel in those cells. Quantitative expression analysis demon-strates a reduction in transcripts for both Sur and the inward rectifying potassium channel (Kir) subunits when IPCs are partially ablated. In summary, we have demonstrated a role for UCP in adult Drosophila IPCs in influencing systemic insulin signaling and longevity by a mechanism that may involve K(ATP) channels.
为了解线粒体解偶联蛋白（UCP）在调节胰岛素信号传导和葡萄糖稳态中的作用，我们构建了在胰岛素产生细胞（IPC）中靶向表达UCP的转基因果蝇品系。IPC中UCP活性增加导致IPC中稳态Ca(2+)水平降低，以及PI3K活性降低和外周FoxO核定位增加。这种全身性胰岛素信号传导的减少伴随着轻度高血糖和寿命延长。为了检验ATP敏感性钾（K(ATP)）通道可能将代谢活性变化（例如，葡萄糖介导的ATP产生或UCP介导的ATP减少）与胰岛素分泌联系起来的假设，我们研究了葡萄糖和特定K(ATP)通道阻滞剂格列本脲对成年IPC膜电位的影响。暴露于葡萄糖会使IPC的膜电位去极化，格列本脲可模拟这种作用，表明K(ATP)通道参与了IPC感知循环血糖变化的机制。此外，正如在哺乳动物β胰腺细胞中所证明的，高葡萄糖会引发成年IPC中强大的Ca(2+)内流。通过原位杂交检测这些细胞中K(ATP)通道的磺酰脲受体（Sur）亚基的转录本，进一步证实了成年IPC中存在功能性K(ATP)通道。定量表达分析表明，当IPC被部分切除时，Sur和内向整流钾通道（Kir）亚基的转录本均减少。总之，我们已经证明UCP在成年果蝇IPC中通过可能涉及K(ATP)通道的机制影响全身性胰岛素信号传导和寿命方面发挥了作用。
