Department of Biology, York University, Toronto, ON, Canada.
PLoS Genet. 2018 Jun 20;14(6):e1007457. doi: 10.1371/journal.pgen.1007457. eCollection 2018 Jun.
The TOR (Target of Rapamycin) pathway is a highly-conserved signaling pathway in eukaryotes that regulates cellular growth and stress responses. The cellular response to amino acids or carbon sources such as glucose requires anchoring of the TOR kinase complex to the lysosomal/vacuolar membrane by the Ragulator (mammals) or EGO (yeast) protein complex. Here we report a connection between the TOR pathway and circadian (daily) rhythmicity. The molecular mechanism of circadian rhythmicity in all eukaryotes has long been thought to be transcription/translation feedback loops (TTFLs). In the model eukaryote Neurospora crassa, a TTFL including FRQ (frequency) and WCC (white collar complex) has been intensively studied. However, it is also well-known that rhythmicity can be seen in the absence of TTFL functioning. We previously isolated uv90 as a mutation that compromises FRQ-less rhythms and also damps the circadian oscillator when FRQ is present. We have now mapped the uv90 gene and identified it as NCU05950, homologous to the TOR pathway proteins EGO1 (yeast) and LAMTOR1 (mammals), and we have named the N. crassa protein VTA (vacuolar TOR-associated protein). The protein is anchored to the outer vacuolar membrane and deletion of putative acylation sites destroys this localization as well as the protein's function in rhythmicity. A deletion of VTA is compromised in its growth responses to amino acids and glucose. We conclude that a key protein in the complex that anchors TOR to the vacuole plays a role in maintaining circadian (daily) rhythmicity. Our results establish a connection between the TOR pathway and circadian rhythms and point towards a network integrating metabolism and the circadian system.
雷帕霉素靶蛋白（TOR）途径是真核生物中高度保守的信号通路，调节细胞生长和应激反应。细胞对氨基酸或碳源（如葡萄糖）的反应需要 TOR 激酶复合物通过 Ragulator（哺乳动物）或 EGO（酵母）蛋白复合物锚定到溶酶体/液泡膜上。在这里，我们报告 TOR 途径与昼夜节律（每日）节律之间的联系。所有真核生物的昼夜节律的分子机制长期以来一直被认为是转录/翻译反馈环（TTFLs）。在模式真核生物粗糙脉孢菌中，包括 FRQ（频率）和 WCC（白 collar 复合物）的 TTFL 已得到深入研究。然而，众所周知，即使没有 TTFL 发挥作用，也可以看到节律性。我们之前分离出 uv90，这是一种突变，会损害 FRQ 缺失的节律，并且在 FRQ 存在时也会抑制生物钟振荡器。我们现在已经定位了 uv90 基因，并将其鉴定为 NCU05950，与 TOR 途径蛋白 EGO1（酵母）和 LAMTOR1（哺乳动物）同源，我们将粗糙脉孢菌蛋白命名为 VTA（液泡 TOR 相关蛋白）。该蛋白锚定在外液泡膜上，删除假定的酰化位点会破坏这种定位以及该蛋白在节律性中的功能。VTA 的缺失会损害其对氨基酸和葡萄糖的生长反应。我们得出结论，锚定 TOR 到液泡的复合物中的关键蛋白在维持昼夜节律（每日）节律中发挥作用。我们的结果建立了 TOR 途径与昼夜节律之间的联系，并指出了一个整合代谢和生物钟系统的网络。
