Amino acid sensing and lysosomal signaling complexes

Area of Science:

• Cellular Biology
• Structural Biology
• Biochemistry

Background:

• Amino acid levels within cells are critical for growth and function.
• Lysosomes play a central role in sensing and responding to amino acid availability.
• Key protein complexes involved in amino acid sensing are being characterized structurally.

Purpose of the Study:

• To provide structural insights into the mechanisms of cellular amino acid sensing.
• To elucidate the regulation of signaling pathways involving Rag GTPases and mTORC1.
• To explore novel lysosomal amino acid sensor systems.

Main Methods:

• X-ray crystallography and cryo-electron microscopy to determine protein structures.
• Biochemical assays to study protein-protein interactions and enzyme activity.
• Cellular imaging to visualize signaling events in vivo.

Main Results:

• Detailed structures of GAP complexes (FLCN-FNIP, GATOR1) regulating Rag GTPases have been determined.
• The arginine transporter SLC38A9 and its role in mTORC1 activation are visualized.
• The structure of GATOR2 reveals a larger scale of amino acid signaling than previously thought.
• mTORC1 substrate recognition mechanisms are more nuanced and specific than appreciated.
• Emerging structural data on the PQLC2 and C9orf72-containing CSW complex.

Conclusions:

• Structural biology is rapidly advancing our understanding of lysosomal amino acid sensing.
• Detailed mechanisms of mTORC1 activation and substrate specificity are being revealed.
• New sensor systems like PQLC2/CSW offer further avenues for research and therapeutic development.