The presenilin loop region is essential for glycogen synthase kinase 3 beta (GSK3 beta) mediated functions on motor proteins during axonal transport

摘要

Neurons require intracellular transport of essential components for function and viability and defects in transport has been implicated in many neurodegenerative diseases including Alzheimer's disease (AD). One possible mechanism by which transport defects could occur is by improper regulation of molecular motors. Previous work showed that reduction of presenilin (PS) or glycogen synthase kinase 3 beta (GSK3 beta) stimulated amyloid precursor protein vesicle motility. Excess GSK3 beta caused transport defects and increased motor binding to membranes, while reduction of PS decreased active GSK3 beta and motor binding to membranes. Here, we report that functional PS and the catalytic loop region of PS is essential for the rescue of GSK3 beta-mediated axonal transport defects. Disruption of PS loop (PS Delta E9) or expression of the non-functional PS variant, PSD447A, failed to rescue axonal blockages in vivo. Further, active GSK3 beta associated with and phosphorylated kinesin-1 in vitro. Our observations together with previous work that showed that the loop region of PS interacts with GSK3 beta propose a scaffolding mechanism for PS in which the loop region sequesters GSK3 beta away from motors for the proper regulation of motor function. These findings are important to uncouple the complex regulatory mechanisms that likely exist for motor activity during axonal transport in vivo.