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Substrate specificity of TOR complex 2 is determined by a ubiquitin-fold domain of the Sin1 subunit

Hisashi Tatebe1, Shinichi Murayama1, Toshiya Yonekura1

  • 1Graduate School of Biological Sciences, Nara Institute of Science and Technology, Nara, Japan.

Elife
|March 7, 2017
PubMed

Insights

The Sin1 protein

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Biochemistry

Background:

  • The target of rapamycin (TOR) protein kinase forms TOR complex 1 (TORC1) and TOR complex 2 (TORC2).
  • Sin1 is a subunit specific to TORC2, crucial for activating AGC-family kinases.
  • TORC2 regulates diverse cellular processes through substrate phosphorylation.

Purpose of the Study:

  • To investigate the role of Sin1 in TORC2 function and substrate recognition.
  • To determine the structural basis for Sin1's interaction with TORC2 substrates.
  • To explore the therapeutic potential of Sin1 in cancer treatment.

Main Methods:

  • Genetic manipulation in fission yeast (sin1 null mutant).
  • Protein domain engineering (Sin1CRIM fusion).
  • Solution structure determination of Sin1CRIM.
  • Biochemical assays for kinase activity and substrate binding.

Main Results:

  • Sin1 is not essential for TORC2 catalytic activity but mediates substrate binding.
  • The Sin1 conserved region in the middle (Sin1CRIM) specifically binds TORC2 substrate kinases.
  • Sin1CRIM can recruit the substrate Gad8 for phosphorylation independently of full-length Sin1.
  • Sin1CRIM possesses a ubiquitin-like fold with an acidic loop critical for substrate interaction.
  • Human Sin1CRIM exhibits conserved substrate-recognition function.

Conclusions:

  • Sin1 acts as a substrate-recognition module within TORC2.
  • The Sin1CRIM domain is a key determinant of TORC2 substrate specificity.
  • Sin1CRIM's conserved function suggests it as a potential drug target for modulating mTORC2 activity, particularly in cancer therapy.
Keywords:
AKTS. pombeSIN1TOR complex 2biochemistrycell biologyhumansubstrate specificitytarget of rapamycin

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