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Updated: Jan 20, 2026
Microscopy of Fission Yeast Sexual Lifecycle
Published on: March 9, 2016
Modulation of TOR complex 2 signaling by the stress-activated MAPK pathway in fission yeast
Susumu Morigasaki1,2, Lit Chein Chin1, Tomoyuki Hatano1
1Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan.
Abstract:
Sin1 is a substrate-binding subunit of target of rapamycin complex 2 (TORC2), an evolutionarily conserved protein kinase complex. In fission yeast, Sin1 has also been identified as a protein that interacts with Spc1 (also known as Sty1) in the stress-activated protein kinase (SAPK) pathway. Therefore, this study examined the relationship between TORC2 and Spc1 signaling. We found that the common docking (CD) domain of Spc1 interacts with a cluster of basic amino acid residues in Sin1. Although diminished TORC2 activity in the absence of the functional Spc1 cascade suggests positive regulation of TORC2 by Spc1, such regulation appears to be independent of the Sin1-Spc1 interaction. Hyperosmotic stress transiently inhibits TORC2, and its swift recovery is dependent on Spc1, the transcription factor Atf1, and the glycelrol-3-phosphate dehydrogenase Gpd1, whose expression is induced upon osmostress by the Spc1-Atf1 pathway. Thus, cellular adaptation to osmostress seems important for TORC2 reactivation, though Spc1 and Atf1 contribute to TORC2 activation also in the absence of osmostress. These results indicate coordinated actions of the SAPK and TORC2 pathways, both of which are essential for fission yeast cells to survive environmental stress.
Insights
The stress-activated protein kinase (SAPK) pathway, involving Spc1, positively regulates target of rapamycin complex 2 (TORC2) in fission yeast. This coordination is crucial for cellular adaptation to environmental stress.
Area of Science:
- Cellular biology
- Molecular biology
- Stress response pathways
Background:
- Sin1 is a subunit of the evolutionarily conserved target of rapamycin complex 2 (TORC2).
- Sin1 interacts with Spc1 (Sty1) in the stress-activated protein kinase (SAPK) pathway in fission yeast.
- The interplay between TORC2 and SAPK signaling in stress adaptation is not fully understood.
Purpose of the Study:
- To investigate the relationship between TORC2 and Spc1 signaling in fission yeast.
- To elucidate the molecular mechanisms underlying the interaction between Sin1 and Spc1.
- To determine the role of Spc1 in TORC2 regulation during stress response.
Main Methods:
- Investigated the interaction between Spc1 and Sin1 using biochemical assays.
- Assessed TORC2 activity in various mutant strains under different stress conditions.
- Analyzed the role of Spc1, Atf1, and Gpd1 in TORC2 reactivation upon hyperosmotic stress.
Main Results:
- Identified an interaction between the common docking (CD) domain of Spc1 and a basic amino acid cluster in Sin1.
- Observed diminished TORC2 activity in the absence of a functional Spc1 cascade, suggesting positive regulation.
- Demonstrated that Spc1, Atf1, and Gpd1 are crucial for TORC2 reactivation following hyperosmotic stress, with Spc1 and Atf1 also contributing to TORC2 activation independently of stress.
Conclusions:
- Spc1 positively regulates TORC2 activity, although this regulation is independent of the direct Sin1-Spc1 interaction.
- Cellular adaptation to osmostress, mediated by the Spc1-Atf1-Gpd1 pathway, is critical for TORC2 reactivation.
- Coordinated signaling between the SAPK and TORC2 pathways is essential for fission yeast survival under environmental stress.
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