Using state of the art imaging technology a team from Yale School of Medicine has glimpsed one of the cell's most important 'nano-machines' in action. The work, performed in collaboration with English and French scientists, provides new insight into the machinery cells use to internalize cell surface receptors.
All cells traffic protein cargos across their outer membrane, and one of the most important routes for cargo internalization is clathrin mediated endocytosis (CME). CME is of fundamental importance for many cellular activities including receptor down-regulation, nutrient uptake and maintenance of signal transmission across nerve cell junctions. Mis-regulation of CME has been implicated in some types of cancer and neuro-degenerative disease and the protein machinery of CME has been co-opted by several viruses, including rabies, as a means of entry into healthy cells.
The researchers led by David Zenisek, assistant professor in the Department of Cellular and Molecular Physiology at Yale School of Medicine, used live cell imaging and a novel fluorescence assay to visualize the formation of clathrin-coated vesicles (CCVs) at single clathrin-coated pits (CCPs) with a time resolution of seconds.
"Although the basic model of clathrin-mediated endocytosis was proposed 41years ago, there are many basic questions outstanding," Zenisek said. "For instance, it wasn't known whether single clathrin coated pits give rise to single clathrin coated vesicles. We have now shown directly that coated pits can produce multiple vesicles in succession."