Ras protein signaling and the control of cell growth

对真核细胞GO样静息状态的彻底描述对于完整的 了解控制细胞增殖的机制。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人的生物学 特别是在酿酒酵母中的静止状态、稳定期。有趣的是，我们发现， Ras/PKA信号传导活性调节自噬，这是一种高度保守的降解途径， 静息细胞存活。自噬对于多细胞生物的正常发育是重要的， 研究已经将这一过程与衰老、程序性细胞死亡、癌症、亨廷顿氏病和 细胞对病原体的反应 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， Atg1蛋白激酶。有趣的是，其他研究表明，Atg1也受到两个额外的调节， 在真核细胞生长控制中起核心作用的信号通路。这后两 这些信号通路涉及高度保守的Tor和AMP激活（Snfl）蛋白激酶。这里的实验 将研究Ras/PKA，Tor和Snf1通路如何共同调节Atg1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， 读出，试图更好地了解这三个信号的活动， 协调这些途径以实现对细胞生长的适当控制。因为自噬机制 高度保守的，很可能，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，如何在临床上操纵这一过程， 对人类有用的方法。 本研究的具体目的是：1）确定PKA磷酸化 调节Atg1蛋白激酶复合物的活性;和2）检查 Ras/PKA、Tor和Snf1信号通路在自噬和细胞生长调控中的作用

A thorough description of the GO-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 (Snfl) 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.