Ras protein signaling and the control of cell growth

描述（由申请人提供）：对真核细胞G 0样静息状态的全面描述对于全面理解控制细胞增殖的机制至关重要。为此，我们一直在研究Ras/cAMP依赖性蛋白激酶（PKA）信号通路如何调节一个特定的静息状态，在酿酒酵母的固定相的生物学。有趣的是，我们发现Ras/PKA信号传导活性调节自噬，这是静息细胞存活所需的高度保守的降解途径。自噬对于多细胞生物体的正常发育是重要的，并且最近的研究已经将该过程与衰老、程序性细胞死亡、癌症、亨廷顿氏病和对病原体的细胞反应联系起来。我们最近的数据表明，Ras/PKA通路直接靶向自噬的关键调节因子Atg 1蛋白激酶。有趣的是，其他工作表明Atg 1还受到另外两种信号通路的调节，这两种信号通路在控制真核细胞生长中发挥核心作用。后两种途径涉及高度保守的Tor和AMP激活（Snf 1）蛋白激酶。这里的实验将研究Ras/PKA，Tor和Snf 1通路如何共同调节Atg 1活性，从而诱导真核细胞中的自噬。此外，我们将使用自噬和其他活动作为读数，试图更好地了解这三种信号通路的活动是如何协调的，以实现对细胞生长的适当控制。由于自噬机制是高度保守的，很可能在这里确定的监管范式将用于其他真核生物。因此，这些研究可以提供重要的见解，了解如何在人类中以临床有用的方式操纵这一过程。该提案的具体目的是：1）确定PKA磷酸化调节Atg 1蛋白激酶复合物活性的机制; 2）检查自噬和细胞生长控制过程中Ras/PKA，Tor和Snf 1信号通路之间的相互作用。

DESCRIPTION (provided by applicant): A thorough description of the G0-like resting states of eukaryotic cells is essential for a complete understanding of the mechanisms controlling cell proliferation. Towards this end, we have been studying how the Ras/cAMP-dependent protein kinase (PKA) signaling pathway regulates the biology of one particular resting state, stationary phase in Saccharomyces cerevisiae. Interestingly, we have found that Ras/PKA signaling activity regulates autophagy, a highly conserved, degradative pathway required for resting cell survival. Autophagy is important for normal development in multicellular organisms and recent studies have linked this process to aging, programmed cell death, cancer, Huntington'.s disease and the cellular response to pathogens. Our recent data indicate that this Ras/PKA pathway directly targets a key regulator of autophagy, the Atg1 protein kinase. Interestingly, other work has shown that Atg1 is also regulated by two additional signaling pathways that have a central role in the control of eukaryotic cell growth. These latter two pathways involve the highly conserved Tor and AMP-activated (Snf1) protein kinases. The experiments here will examine how the Ras/PKA, Tor and Snf1 pathways work together to regulate Atg1 activity, and thus the induction of autophagy in eukaryotic cells. In addition, we will use autophagy, and other activities, as readouts in an attempt to develop a better understanding of how the activities of these three signaling pathways are coordinated to bring about the proper control of cell growth. Since the autophagy machinery is highly conserved, it is likely that the regulatory paradigms identified here will be used in other eukaryotes. Thus, these studies could provide important insights into how this process might be manipulated in clinically useful ways in humans. The Specific Aims of this proposal are: 1) to determine the mechanism by which PKA phosphorylation regulates the activity of the Atg1 protein kinase complex; and 2) to examine the interplay between the Ras/PKA, Tor and Snf1 signaling pathways during the control of autophagy and cell growth.