Department of Microbiology, Immunology and Molecular Genetics, Molecular Biology Institute, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA 90095-1489, USA.
J Cell Sci. 2010 Mar 1;123(Pt 5):777-86. doi: 10.1242/jcs.060319. Epub 2010 Feb 9.
Cellular activities are regulated by environmental stimuli through protein phosphorylation. Target of rapamycin (TOR), a serine/threonine kinase, plays pivotal roles in cell proliferation and cell growth in response to nutrient status. In Schizosaccharomyces pombe, TORC1, which contains Tor2, plays crucial roles in nutrient response. Here we find a nitrogen-regulated phosphoprotein, p27, in S. pombe using the phospho-Akt substrate antibody. Response of p27 phosphorylation to nitrogen availability is mediated by TORC1 and the TSC-Rhb1 signaling, but not by TORC2 or other nutrient stress-related pathways. Database and biochemical analyses indicate that p27 is identical to ribosomal protein S6 (Rps6). Ser235 and Ser236 in Rps6 are necessary for Rps6 phosphorylation by TORC1. These Rps6 phosphorylations are dispensable for cell viability. Rps6 phosphorylation by TORC1 also responds to availability of glucose and is inhibited by osmotic and oxidative stresses. Rapamycin inhibits the ability of TORC1 to phosphorylate Rps6, owing to interaction of the rapamycin-FKBP12 complex with the FRB domain in Tor2. Rapamycin also leads to a decrease in cell size in a TORC1-dependent manner. Our findings demonstrate that the nutrient-responsive and rapamycin-sensitive TORC1-S6 signaling exists in S. pombe, and that this pathway plays a role in cell size control.
细胞活动受环境刺激通过蛋白质磷酸化来调节。雷帕霉素靶蛋白（TOR）是一种丝氨酸/苏氨酸激酶，在响应营养状态的细胞增殖和细胞生长中发挥关键作用。在裂殖酵母中，包含 Tor2 的 TORC1 在营养响应中发挥关键作用。在这里，我们使用磷酸化 Akt 底物抗体在 S. pombe 中发现了一种氮调节的磷酸蛋白 p27。p27 磷酸化对氮可用性的反应是由 TORC1 和 TSC-Rhb1 信号介导的，但不是由 TORC2 或其他与营养应激相关的途径介导的。数据库和生化分析表明，p27 与核糖体蛋白 S6（Rps6）相同。Rps6 中的 Ser235 和 Ser236 对于 TORC1 对 Rps6 的磷酸化是必需的。这些 Rps6 磷酸化对于细胞活力不是必需的。TORC1 对 Rps6 的磷酸化也响应葡萄糖的可用性，并受到渗透和氧化应激的抑制。雷帕霉素抑制 TORC1 磷酸化 Rps6 的能力，这归因于雷帕霉素-FKBP12 复合物与 Tor2 的 FRB 结构域的相互作用。雷帕霉素也以 TORC1 依赖的方式导致细胞大小减小。我们的发现表明，营养响应和雷帕霉素敏感的 TORC1-S6 信号存在于 S. pombe 中，并且该途径在细胞大小控制中发挥作用。
