BBB seminar: Gary Banker
Membrane trafficking and neuronal polarity
Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, Portland, OR, USA
Nearly every aspect of neuronal function depends on the accurate polarization of membrane proteins to axons or dendrites. We have been attempting to identify the principal trafficking pathways that underlie the polarized localization of neuronal plasma membrane proteins and have developed methods to image in living cells the principal populations of the long-range carriers that transport proteins along these pathways. Our results show that there are multiple populations of Golgi-derived carriers that deliver different dendritic proteins, but all share one key feature - they are transported into dendrites but excluded from axons. Carriers containing axonal proteins enter both dendrites and axons, but are preferentially transported into axons. Thus the selectivity of anterograde transport, which is mediated by kinesin motor proteins, lies at the heart of neuronal polarity. Using an assay based on imaging the accumulation of truncated, constitutively active kinesins in living cells, we demonstrated that kinesin-1 motor domains translocate preferentially into the axon whereas a kinesin-3 motor domain translocates with equal efficiency into both axons and dendrites. Early in development, before axon specification, kinesin-1 translocates first into one neurite, then into another, which implies that the molecular differences that mark different microtubule populations in neurons can be rapidly modulated.