Mechanistic analysis of microtubule catastrophe

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This project seeks to discover, in one model system, how collective dynamic behaviors of parts of living cells are determined by the structural and biochemical properties of the individual components. Microtubules will be used as the model system for this research. Microtubules are polymers made from a protein called αβ-tubulin, and they play essential roles in organizing the inside of the cell and in partitioning the genetic material during cell division. By integrating diverse approaches this research will decipher and quantify the connections between the underlying structural and biochemical properties of individual αβ-tubulin proteins and the complex polymerization dynamics that emerges from their collective interactions. In addition to advancing the understanding of a process of fundamental importance to cell biology, the project emphasizes educational impact. Graduate students working on the project will receive interdisciplinary training. An outreach partnership with a local elementary school will expose underrepresented and economically disadvantaged students to the fun of doing science while providing them and their teachers with access to high-tech but relatively inexpensive digital microscopes to facilitate inquiry-based learning and discovery. These outreach activities will also provide new opportunities for graduate students, postdoctoral fellows, and other members of the UT Southwestern community to become involved in science education.The specific problem to be studied is microtubule catastrophe, the sporadic switch from microtubule growing to microtubule shrinking. The goal is to provide a convincing and testable molecular explanation for experimental measurements of catastrophe, specifically how frequently catastrophe occurs as a function of the concentration of the polymerizing αβ-tubulin subunits. The research will combine a variety of approaches including predictive computational simulations, use of mechanism-specific site-directed mutants of αβ-tubulin, and in vitro biochemistry and reconstitution. Using this set of tools, we will (i) incorporate three different biochemical mechanisms into a computational model for microtubule dynamics and determine how each mechanism affects prediction of catastrophe; (ii) perform experimental tests for neighbor coupling in the microtubule lattice, something that has been hypothesized to occur but that has not been previously testable; and (iii) measure how mutations to an interacting triad of residues that is conserved in α- and β-tubulin affect microtubule polymerization dynamics and the conformation(s) of αβ-tubulin inside and outside the microtubule. Together, these approaches will address outstanding questions about the fundamental mechanisms of microtubule dynamics.This project is jointly funded by the Molecular Biophysics and Cellular Dynamics and Function clusters in the Division of Molecular and Cellular Biosciences.