Structural insights into TSC complex assembly and GAP activity on Rheb

Nat Commun. 2021 Jan 12;12(1):339. doi: 10.1038/s41467-020-20522-4.

Abstract

Tuberous sclerosis complex (TSC) integrates upstream stimuli and regulates cell growth by controlling the activity of mTORC1. TSC complex functions as a GTPase-activating protein (GAP) towards small GTPase Rheb and inhibits Rheb-mediated activation of mTORC1. Mutations in TSC genes cause tuberous sclerosis. In this study, the near-atomic resolution structure of human TSC complex reveals an arch-shaped architecture, with a 2:2:1 stoichiometry of TSC1, TSC2, and TBC1D7. This asymmetric complex consists of two interweaved TSC1 coiled-coil and one TBC1D7 that spans over the tail-to-tail TSC2 dimer. The two TSC2 GAP domains are symmetrically cradled within the core module formed by TSC2 dimerization domain and central coiled-coil of TSC1. Structural and biochemical analyses reveal TSC2 GAP-Rheb complimentary interactions and suggest a catalytic mechanism, by which an asparagine thumb (N1643) stabilizes γ-phosphate of GTP and accelerate GTP hydrolysis of Rheb. Our study reveals mechanisms of TSC complex assembly and GAP activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biocatalysis
  • GTPase-Activating Proteins / metabolism*
  • HEK293 Cells
  • Humans
  • Models, Molecular
  • Protein Binding
  • Protein Domains
  • Protein Multimerization
  • Ras Homolog Enriched in Brain Protein / metabolism*
  • Tuberous Sclerosis Complex 1 Protein / chemistry*
  • Tuberous Sclerosis Complex 1 Protein / metabolism*
  • Tuberous Sclerosis Complex 1 Protein / ultrastructure
  • Tuberous Sclerosis Complex 2 Protein / chemistry*
  • Tuberous Sclerosis Complex 2 Protein / metabolism*
  • Tuberous Sclerosis Complex 2 Protein / ultrastructure

Substances

  • GTPase-Activating Proteins
  • Ras Homolog Enriched in Brain Protein
  • Tuberous Sclerosis Complex 1 Protein
  • Tuberous Sclerosis Complex 2 Protein