UCSB Researchers Discover That The Cell's Endosomes Use A Surprising Transportation System

By marking endosomes with fluorescent tags and watching them move inlive cells, Samir Mitragotri, a UCSB professor of chemical engineering,and graduate students Chinmay Pangarkar and Anh Tuan Dinh learned thatthe endosomes travel to the cell's nucleus using back-and-forthsymmetrical movement, rather than taking a more direct route. Thisforward and reverse motion leads to even distribution of the endosomeson microtubules.

An aster-like layout of the microtubules helps the endosomes accumulateat the nucleus. The researchers think this non-direct approach to thenucleus has evolved to allow hundreds of endosomes to bring nutrientsand molecular information to the cell's center for processing. Even ifthe cell moves or if there's increased traffic flow, there's never atraffic jam on the microtubules.

While it has long been known that endosomes travel in a bidirectionalway, it has not previously been established that the transport systemis symmetrical. The authors believe that because a number ofneurological, muscular and cardiac diseases stem from themalfunctioning of one or more proteins that regulate the transportproperties of endosomes or lysosomes, it may be possible to perform insilico and/or laboratory experiments to better understand therelationship between transport properties and pathology.

The delivery of many therapeutic agents, especially DNA and siRNA isdependent on endocytic transport. Understnading how endosomedistribution evolves is central to such therapeutic approaches.