Metabolic regulation via intramitochondrial sAC

描述(由申请人提供)：cAMP在独立调节的信号微域中发挥局部作用已被广泛接受。可溶性腺酰环化酶(SAC)在分子、生化和功能上不同于其他已知的哺乳动物cAMP来源，即跨膜腺苷酸环化酶(TmACs)。TmAC定位在质膜上，受细胞外信号(如激素和神经递质)的异源三聚体G蛋白调节，而SAC分布于细胞质和包括线粒体在内的细胞内，在那里它准备提供第二信使，调节cAMP的细胞内和细胞器内靶标。在线粒体内部，由SAC产生的cAMP调节电子传递链(ETC)的组成部分，增加电子通量和ATP合成的总体速率。这种线粒体内SAC-cAMP信号通路将细胞营养利用与能量产生联系起来，定义了氧化磷酸化的短期调节机制，使细胞的呼吸机制能够对营养可获得性、环境条件和能量需求的瞬时变化做出反应。在这一应用中，我们建议阐明这一途径的生理意义。我们建议(1)使用药物抑制剂和来自SAC-C1KO小鼠的细胞来确定在培养细胞中线粒体内SAC-cAMP途径的慢性和急性丧失的后果；以及(2)辨别在SAC-C1KO小鼠中看到的已知代谢表型中的哪些是由线粒体内SAC-cAMP途径的丧失引起的。了解这一途径的作用可能对细胞内在营养感知、糖尿病和代谢具有重要意义，并将揭示这一细胞内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.