Structure and Mechanism of the Kinesin-3 Motor KIF1A

Our goal is to define the structural and functional mechanism by which the kinesin-3 motor KIF1A generates force and moves along microtubules, and to define the structural basis of KIF1A-related human diseases. The microtubule (MT) transport system regulates essential eukaryotic activities, including neuronal cell division, neuronal migration and the transport of subcellular cargoes. KIF1A, a member of the kinesin-3 family of MT-associated motor proteins, is a key mediator of these activities as the major generator of MT plus-end-directed motility in neurons. KIF1A’s cargoes include nuclei in dividing brain stem cells and synaptic vesicle precursors and dense core vesicles in axon terminals. Not surprisingly, its dysfunction is implicated in a growing number of neurodevelopmental and neurodegenerative disorders referred to as KIF1A-associated neurological disorder (KAND). Unfortunately, these diseases remain poorly understood, in part because KIF1A’s molecular mechanism remains unclear. For example, while most mutations occur in KIF1A’s motor domain, high-resolution structures of the KIF1A-MT complex do not exist. In addition, it remains unknown why Kif1A is superprocessive but easily gives up under load. In this proposal, we will combine cryo-electron microscopy, single-molecule fluorescence, and optical tweezers-based force measurements with innovative protein engineering to determine why KIF1A is a weak but superprocessive motor, define high-resolution structures of the KIF1A-MT complex as a function of KIF1A’s mechanochemical cycle and determine the structural defects caused by disease mutations in KIF1A. These studies will provide a new understanding of KAND and elucidate molecular targets for therapeutic interventions.