Endocytosis is a process by which macromolecules, receptors, transporters, and channels are recycled via internalization of the plasma membrane. Endocytosis at synapses, called synaptic vesicle endocytosis, supports the rapid recovery of vesicles during neurotransmission. Clathrin-mediated endocytosis occurs ~ 30 s after stimulation, however using ?flash-and-freeze? electron microscopy we have demonstrated endocytosis at 30 ? 300 ms after stimulation in both mouse hippocampal neurons as well as C. elegans neuromuscular junctions. Further, the process is clathrin independent. Ultrafast endocytosis generates a large endosome, which much be sorted into new synaptic vesicles or targeted for degradation in the lysosomes. Sorting of the endosome requires clathrin, but it is not clear which proteins act on the endosome to target these vesicles. The clathrin binding adaptor proteins AP1, AP2, and AP3 have all been implicated in synaptic function and targeting of membrane bound compartments. AP2 is thought to regenerate synaptic vesicles, while AP1 and AP3 are thought to target vesicles to the plasma membrane or the lysosome, respectively. The goal of this fellowship is to determine the role of these adaptor proteins in endosomal sorting and regeneration of synaptic vesicles during ultrafast endocytosis.
Endocytosis is a mechanism by which neurons recycle essential components, such as neurotransmitters and receptors. Disruption of this process may underlie many neurodegenerative diseases, including Huntington?s Disease, the ataxias, Parkinson?s Disease, Hermansky?Pudlack syndrome, and Alzheimer?s Disease. The aim of this project is to use cell-biological, biochemical, and genetic approaches to investigate the fundamental mechanisms underlying this core biological process, which remains unresolved.
