Metabolic regulation via intramitochondrial sAC

描述（由申请人提供）：cAMP在独立调控的信号微域中局部起作用已被广泛接受。可溶性腺苷酸环化酶（sAC）在分子、生化和功能上都不同于其他已知的哺乳动物cAMP来源，即跨膜腺苷酸环化酶（tmac）。tmac位于质膜上，受到异源三聚体G蛋白的调控，以响应细胞外信号，如激素和神经递质，而sAC则分布在整个细胞质和细胞内，包括线粒体，在那里它准备提供调节细胞内和细胞器内cAMP靶点的第二信使。在线粒体内，sac产生的cAMP调节电子传递链（ETC）的组分，增加电子通量和ATP合成的总体速率。这种将细胞营养利用与能量产生联系起来的线粒体内sAC-cAMP信号通路定义了一种氧化磷酸化的短期调节机制，该机制允许细胞的呼吸机制对营养可利用性、环境条件和能量需求的短暂变化做出反应。在本应用中，我们建议阐明该通路的生理意义。我们建议(1)使用药理学抑制剂和来自sAC-C1 KO小鼠的细胞来确定慢性和急性切断培养细胞线粒体内sAC-cAMP通路的后果；(2)在sAC-C1型KO小鼠中观察到的已知代谢表型中，哪些是由线粒体内sAC-cAMP通路的缺失引起的。了解这一途径的作用可能对细胞内在营养感知、糖尿病和一般代谢具有重要意义，并将揭示这种细胞内cAMP微域的功能意义。

DESCRIPTION (provided by applicant): It has become widely accepted that cAMP acts locally, in independently regulated signaling microdomains. Soluble adenylyl cyclase (sAC) is molecularly, biochemically and functionally distinct from the other known mammalian sources of cAMP, the transmembrane adenylyl cyclases (tmACs). While tmACs are positioned at the plasma membrane where they are regulated by heterotrimeric G proteins in response to extracellular cues such as hormones and neurotransmitters, sAC is distributed throughout the cytoplasm and in intracellular compartments, including mitochondria, where it is poised to provide the second messenger regulating the intracellular and intra-organellar targets of cAMP. Inside mitochondria, sAC-generated cAMP regulates components of the electron transport chain (ETC), increasing electron flux and the overall rate of ATP synthesis. This intramitochondrial sAC-cAMP signaling pathway linking cellular nutrient utilization with energy production defines a mechanism of short-term modulation of oxidative phosphorylation which allows the cell's respiratory machinery to respond to transient changes in nutritional availability, environmental conditions, and energy requirements. In this application, we propose to elucidate the physiological significance of this pathway. We propose to (1) determine the consequences of both chronic and acute abrogation of the intramitochondrial sAC-cAMP pathway in cultured cells using pharmacological inhibitors and cells derived from sAC-C1 KO mice; and (2) discern which of the known metabolic phenotypes seen in sAC-C1 KO mice are caused by abrogation of the intramitochondrial sAC-cAMP pathway. Understanding the role of this pathway is likely to have important implications for cell intrinsic nutrient sensing, diabetes, and metabolism in general, and it will reveal the functional significance of this intracellular cAMP microdomain.