MCCs are linear invaginations of the yeast plasma membrane that form stable membrane microdomains. Although over 20 proteins are localized in the MCCs, it is not well understood how these proteins coordinately maintain normal MCC function. Pil1 is a core eisosome protein and is responsible for MCC-invaginated structures. In addition, six-tetraspan membrane proteins (6-Tsp) are localized in the MCCs and classified into two families, the Sur7 family and Nce102 family. To understand the coordinated function of these MCC proteins, single and multiple deletion mutants of Pil1 and 6-Tsp were generated and their MCC structure and growth under various stresses were investigated. Genetic interaction analysis revealed that the Sur7 family and Nce102 function in stress tolerance and normal eisosome assembly, respectively, by cooperating with Pil1. To further understand the role of MCCs/eisosomes in stress tolerance, we screened for suppressor mutants using the SDS-sensitive phenotype of pil1Δ 6-tspΔ cells. This revealed that SDS sensitivity is caused by hyperactivation of Tor kinase complex 2 (TORC2)-Ypk1 signaling. Interestingly, inhibition of sphingolipid metabolism, a well-known downstream pathway of TORC2-Ypk1 signaling, did not rescue the SDS-sensitivity of pil1Δ 6-tspΔ cells. These results suggest that Pil1 and 6-Tsp cooperatively regulate TORC2 signaling during the stress response.

中文翻译：

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MCC/异构体相关蛋白、Pil1和四跨膜蛋白在应激反应过程中协调调节TORC2信号

MCC 是酵母质膜的线性内陷，形成稳定的膜微区。尽管有超过 20 种蛋白质位于 MCC 中，但尚不清楚这些蛋白质如何协同维持正常的 MCC 功能。Pil1 是核心异构体蛋白，负责 MCC 内陷结构。此外，六四跨膜蛋白 (6-Tsp) 位于 MCC 中并分为两个家族，即 Sur7 家族和 Nce102 家族。为了了解这些 MCC 蛋白的协调功能，产生了 Pil1 和 6-Tsp 的单个和多个缺失突变体，并研究了它们在各种胁迫下的 MCC 结构和生长。遗传相互作用分析表明，Sur7 家族和 Nce102 分别通过与 Pil1 合作，在胁迫耐受和正常的 eisosome 组装中发挥作用。pil1 Δ 6-tsp Δ 细胞。这表明 SDS 敏感性是由 Tor 激酶复合物 2 (TORC2)-Ypk1 信号传导的过度激活引起的。有趣的是，抑制鞘脂代谢（一种众所周知的 TORC2-Ypk1 信号传导的下游途径）并不能挽救pil1 Δ 6-tsp Δ 细胞的 SDS 敏感性。这些结果表明 Pil1 和 6-Tsp 在应激反应过程中协同调节 TORC2 信号传导。