Molecular basis of Fidgetin family functional diversity

The dynamic microtubule cytoskeleton is essential for cellular function, and its disruption leads to severe human diseases. Microtubule-severing enzymes are key in ensuring the dynamism of the microtubule network. These enzymes function by removing tubulin, the building blocks of microtubules, from the microtubule lattice. The Fidgetin family of microtubule-severing enzymes (FIGN, FIGNL1, FIGNL2) are key regulators of microtubules, but the molecular mechanisms behind their diverse functions are unknown. I propose a multi-disciplinary approach to bridge this knowledge gap. First, I will use in vitro reconstitution and microscopy to quantify the unique enzymatic activities of each Fidgetin protein and their response to the tubulin code. Second, I will use gene editing to map their subcellular locations and determine the function of their constituent domains in live cells. Finally, I will use cryo-EM, and advanced machine-learning processing tools, to reveal the molecular mechanism linking ATP hydrolysis to microtubule severing at the atomic level. This integrated study using complementary approaches will provide important insights into the regulation of the microtubule cytoskeleton by the Fidgetin enzymes, clarifying their roles in health and disease.