Bidirectional translocation of neurofilaments along microtubules mediated in part by dynein/dynactin

Neuronal cytoskeletal elements such as neurofilaments, F-actin, and microtu bules are actively translocated by an as yet unidentified mechanism. This r eport describes a novel interaction between neurofilaments and microtubule motor proteins that mediates the translocation of neurofilaments along micr otubules in vitro. Native neurofilaments purified from spinal cord are tran sported along microtubules at rates of 100-1000 nm/s to both plus and minus ends. This motion requires ATP and is partially inhibited by vanadate, con sistent with the activity of neurofilament-bound molecular motors. Motility is in part mediated by the dynein/dynactin motor complex and several kines in-like proteins. This reconstituted motile system suggests how slow net mo vement of cytoskeletal polymers may be achieved by alternating activities o f fast microtubule motors.