GATOR1 Mutations Impair PI3 Kinase-Dependent Growth Factor Signaling Regulation of mTORC1

Area of Science:

• Cellular Biology
• Molecular Biology
• Genetics

Background:

• GATOR1 complex regulates mTORC1 signaling based on amino acid availability.
• Mutations in GATOR1 subunits (NPRL2, NPRL3, DEPDC5) are linked to human epilepsy.
• The precise impact of these mutations on GATOR1 function and mTORC1 regulation remains unclear.

Purpose of the Study:

• Investigate the effects of epilepsy-associated NPRL2 mutations on GATOR1 complex assembly and mTORC1 signaling.
• Determine how these mutations affect mTORC1 regulation in response to amino acid availability and growth factor signaling.
• Elucidate the functional consequences of GATOR1 complex disruption in cellular processes.

Main Methods:

• Site-directed mutagenesis to create NPRL2 epilepsy-linked mutants (L105P, T110S, D214H).
• Cell culture experiments to assess mTORC1 activity, protein-protein interactions, and complex assembly.
• Analysis of cellular responses to amino acid deprivation, growth factor withdrawal, and PI3K inhibition.
• Western blotting and immunofluorescence to evaluate protein levels, signaling pathways, and TFEB localization.

Main Results:

• Epilepsy-linked NPRL2 mutations (L105P, T110S, D214H) increase basal mTORC1 signaling.
• The NPRL2-L105P mutation impairs GATOR1 complex assembly by disrupting interactions with NPRL3 and DEPDC5, causing constitutive mTORC1 activity.
• The GATOR1 complex is essential for inhibiting mTORC1 in response to growth factor withdrawal or PI3K inhibition.
• Cells lacking functional GATOR1 are resistant to PI3K-dependent mTORC1 inhibition, leading to sustained translation and altered TFEB nuclear localization.

Conclusions:

• Epilepsy-associated NPRL2 mutations can disrupt GATOR1 complex assembly, leading to aberrant mTORC1 signaling.
• These mutations impair the normal regulation of mTORC1 by both amino acid and growth factor pathways.
• The findings provide a molecular link between GATOR1 dysfunction, mTORC1 dysregulation, and epilepsy pathogenesis.