Coordinated regulation of TORC2 signaling by MCC/eisosome‐associated proteins, Pil1 and tetraspan membrane proteins during the stress response

• Published in: Molecular microbiology 2022-05, Vol.117 (5), p.1227-1244
• Main Authors: Sakata, Ken‐taro, Hashii, Keisuke, Yoshizawa, Koushiro, Tahara, Yuhei O., Yae, Kaori, Tsuda, Ryohei, Tanaka, Naotaka, Maeda, Tatsuya, Miyata, Makoto, Tabuchi, Mitsuaki
• Format: Article
• Language: English
• Subjects: Cell Membrane - metabolism; Deletion mutant; eisosome; Genetic analysis; Invaginations; Kinases; Lipid metabolism; Mechanistic Target of Rapamycin Complex 2 - metabolism; Membrane Microdomains - metabolism; Membrane proteins; Membrane Proteins - genetics; Membrane Proteins - metabolism; Membranes; microdomain; Phenotypes; Phosphoproteins - metabolism; plasma membrane; Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - metabolism; Sensitivity; Signaling; stress tolerance; Suppressor mutant; TORC2; Yeasts
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.14903

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. MCC/Eisosomes are linear invaginations of the plasma membrane of yeast. Pil1, a core protein of the eisosome, and six tetraspan membrane proteins (6‐Tsp) are localized in the MCC/eisosome. Based on their homology, 6‐Tsp are classified into two families, Sur7 and Nce102. These protein families have distinct roles: the Sur7 family functions in the stress response against plasma membrane/cell wall damaging agents, such as SDS, by negatively regulating the TORC2‐Ypk1 pathway, and Nce102 is involved in normal eisosome assembly by cooperating with Pil1.