Filament formation drives catalysis by glutaminase enzymes important in cancer progression

Area of Science:

• Biochemistry
• Structural Biology
• Cancer Biology

Background:

• Glutaminase enzymes (GAC and GLS2) are key in cancer cell metabolism, utilizing glutamine.
• Understanding their activation and catalytic mechanisms is vital for anti-cancer drug development.
• Previous studies lacked clarity on how these enzymes function at a molecular level.

Purpose of the Study:

• To elucidate the mechanism of activation and catalytic activity of GAC and GLS2.
• To present the cryo-EM structures of GAC and GLS2, revealing essential conformational states.
• To investigate the role of filament formation in glutaminase activity.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine enzyme structures.
• Biochemical assays to assess catalytic activity and filament formation.
• Analysis of enzyme conformational changes linked to catalysis.

Main Results:

• Glutaminase (GAC and GLS2) filament formation is directly coupled to catalytic activity.
• Cryo-EM structures reveal conformational states essential for catalysis, including an 'activation loop' and 'lid' mechanism.
• Ankyrin repeats on GLS2 regulate enzymatic activity; activators stabilize, and inhibitors block, filament formation.

Conclusions:

• Filament formation is a key regulatory mechanism for glutaminase activity.
• The structural insights provide a basis for understanding glutaminolysis in cancer progression.
• Targeting glutaminase filament formation offers a promising strategy for anti-cancer drug development.