As first demonstrated in budding yeast (Saccharomyces cerevisiae), all eukaryotic cells contain two, distinct multi-component protein kinase complexes that each harbor the TOR (Target Of Rapamycin) polypeptide as the catalytic subunit. These ensembles, dubbed TORC1 and TORC2, function as universal, centrally important sensors, integrators, and controllers of eukaryotic cell growth and homeostasis. TORC1, activated on the cytosolic surface of the lysosome (or, in yeast, on the cytosolic surface of the vacuole), has emerged as a primary nutrient sensor that promotes cellular biosynthesis and suppresses autophagy. TORC2, located primarily at the plasma membrane, plays a major role in maintaining the proper levels and bilayer distribution of all plasma membrane components (sphingolipids, glycerophospholipids, sterols, and integral membrane proteins). This article surveys what we have learned about signaling via the TORC2 complex, largely through studies conducted in S. cerevisiae. In this yeast, conditions that challenge plasma membrane integrity can, depending on the nature of the stress, stimulate or inhibit TORC2, resulting in, respectively, up-regulation or down-regulation of the phosphorylation and thus the activity of its essential downstream effector the AGC family protein kinase Ypk1. Through the ensuing effect on the efficiency with which Ypk1 phosphorylates multiple substrates that control diverse processes, membrane homeostasis is maintained. Thus, the major focus here is on TORC2, Ypk1, and the multifarious targets of Ypk1 and how the functions of these substrates are regulated by their Ypk1-mediated phosphorylation, with emphasis on recent advances in our understanding of these processes.

中文翻译：

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TOR 复合物 2 是质膜稳态的主要调节因子


正如在芽殖酵母（酿酒酵母）中首次证明的那样，所有真核细胞都含有两种不同的多组分蛋白激酶复合物，每个复合物都含有 TOR（雷帕霉素靶标）多肽作为催化亚基。这些被称为 TORC1 和 TORC2 的整体，充当真核细胞生长和稳态的通用且重要的传感器、集成器和控制器。 TORC1 在溶酶体的胞质表面（或者在酵母中，在液泡的胞质表面）被激活，已成为促进细胞生物合成和抑制自噬的主要营养传感器。 TORC2 主要位于质膜，在维持所有质膜成分（鞘脂、甘油磷脂、甾醇和整合膜蛋白）的适当水平和双层分布方面发挥着重要作用。本文调查了我们对 TORC2 复合物信号传导的了解，主要是通过在酿酒酵母中进行的研究。在这种酵母中，挑战质膜完整性的条件可以根据应激的性质刺激或抑制TORC2，分别导致磷酸化的上调或下调，从而导致其重要下游效应子的活性AGC 家族蛋白激酶 Ypk1。通过随后对 Ypk1 磷酸化控制不同过程的多种底物的效率的影响，维持膜稳态。因此，这里的主要焦点是 TORC2、Ypk1 和 Ypk1 的多种靶标，以及这些底物的功能如何通过 Ypk1 介导的磷酸化来调节，重点是我们对这些过程的理解的最新进展。