Project Summary/Abstract: Microtubules are critical for nearly every function of eukaryotic cells, from their ability to divide and move to their ability to adopt specific morphologies and withstand mechanical forces. Microtubule assembly, dynamics, and functions are dictated and regulated by a large number of cellular factors including microtubule associated proteins (MAPs) and molecular motors in the kinesin and dynein superfamilies. Our overall goal is to define the mechanisms by which microtubules and kinesin motor proteins drive intracellular trafficking in mammalian cells. Unresolved questions include: What are the motility and force-generating properties of different kinesins that enable them to perform specific motor functions in cells? How are posttranslational modifications of tubulin subunits within a subset of microtubules recognized as “road signs” for kinesin-based trafficking? What is the fate of the motor at the end of its journey i.e., is it degraded or recycled? What effect does motor stepping have on the microtubule lattice? To address these questions, we will combine biophysical and biochemical methods that provide mechanistic detail on motor mechanics and motility with cellular assays that report on regulation and function within the complex cellular environment. As defects in microtubules and kinesin motors are linked to developmental disorders, neurodegenerative diseases, and cancer, these studies will advance our understanding of their functions in cell biology and disease.