ACTION OF BREFELDIN-A ON AMPHIBIAN NEURONS - PASSAGE OF NEWLY SYNTHESIZED PROTEINS THROUGH THE GOLGI-COMPLEX IS NOT REQUIRED FOR CONTINUED FAST ORGANELLE TRANSPORT IN AXONS

The relation between the availability of newly synthesized protein and lipid and the axonal transport of optically detectable organelles was examined in peripheral nerve preparations of amphibia (Rana catesbeia na and Xenopus laevis) in which intracellular traffic from the endopla smic reticulum to the Golgi complex was inhibited with brefeldin A (BF A). Accumulation of fast-transported radio-labeled protein or phosphol ipid proximal to a sciatic nerve ligature was monitored in vitro in pr eparations of dorsal root ganglia and sciatic nerve. Organelle transpo rt was examined by computer-enhanced video microscopy of single myelin ated axons. BFA reduced the amount of radiolabeled protein and lipid e ntering the fast-transport system of the axon without affecting either the synthesis or the transport rate of these molecules. The time cour se of the effect of BFA on axonal transport is consistent with an acti on at an early step in the intrasomal pathway, and with its action bei ng related to the observed rapid (<1 h) disassembly of the Golgi compl ex. At a concentration of BFA that reduced fast-transported protein by >95%, no effect was observed on the flux or velocity of anterograde o r retrograde organelle transport in axons for at least 20 h. Bidirecti onal axonal transport of organelles was similarly unaffected following suppression of protein synthesis by >99%. The findings suggest that t he anterograde flux of transport organelles is not critically dependen t on a supply of newly synthesized membrane precursors. The possibilit ies are considered that anterograde organelles normally arise from mem brane components supplied from a post-Golgi storage pool, as well as f rom recycled retrograde organelles.