Structure of the human TSC:WIPI3 lysosomal recruitment complex

Area of Science:

• Biochemistry
• Cell Biology
• Structural Biology

Background:

• Tuberous sclerosis complex (TSC) regulates mTORC1 signaling by hydrolyzing GTP from RHEB.
• Loss-of-function mutations in TSC lead to TSC disease, characterized by uncontrolled tumor growth.
• TSC functions at the lysosomal membrane to inhibit mTORC1.

Purpose of the Study:

• To determine the high-resolution cryo-electron microscopy (cryo-EM) structure of human TSC in complex with WIPI3.
• To elucidate the mechanism of TSC recruitment to the lysosomal membrane.
• To understand how TSC dysregulation contributes to disease.

Main Methods:

• Cryo-electron microscopy (cryo-EM) at 2.8-Å resolution.
• Structural analysis of the complete human TSC complexed with WIPI3.
• Biochemical assays to characterize PIP binding.

Main Results:

• A novel amino-terminal TSC1 HEAT repeat dimer was identified, clamping onto TSC and forming a PIP-binding pocket.
• This pocket specifically binds monophosphorylated phosphoinositides (PIPs).
• The structure provides a model for WIPI3 and PIPs recruiting TSC to the lysosomal membrane to inhibit mTORC1.

Conclusions:

• The high-resolution TSC structure reveals new insights into its function and regulation.
• Structural findings highlight previously unrecognized mutational hotspots in TSC.
• This work advances our understanding of TSC dysregulation in disease and potential therapeutic strategies.