Axonal transport often breaks down and many neurodegenerative diseases are characterized by defects in this process. Of particular interest is a group of transported proteins called slow component-b that includes synuclein and tau, disease proteins involved in Parkinson’s and Alzheimer’s disease, respectively, in addition to many other proteins critical for axonal growth and regeneration.
"There are two basic transport groups called fast and slow components, with a 200 to 300 fold difference in average velocities," says first author Subhojit Roy, MD, PhD, a neuropathologist and Research Associate in the Department of Pathology and Laboratory Medicine. "While scientists have seen proteins in the fast component move rapidly to the tip of the axon, until now, mechanisms of the slow movement of these disease-related proteins have been unclear as their transport had not been directly visualized."
Roy devised a system to simultaneously visualize the transport of two labeled slow-component-b proteins in living cultured mouse axons. This clarified unique aspects of slow-protein transport. He found that the "slow" proteins actually showed rapid bursts of movement followed by pauses. This intermittent transport behavior of individual cargoes made the overall population slow and suggests that fast and slow proteins use the same basic mechanisms for transport.
Surprisingly, the videos also revealed that multiple slow proteins are transported together as "packets," essentially piggy-backing on each other, possibly
Source:University of Pennsylvania School of Medicine