Axon membrane flows from the growth cone to the cell body

Abstract

During the growth of axons, the surface area of the neuron increases dramatically. Membrane addition as well as exchange could contribute to rapid membrane dynamics or flow. Using diffusing latex beads to monitor membrane flow, we find that axonal membrane flows rapidly (7 microns/min) from growth cone to cell body during axon growth and that flow is inhibited by brefeldin A. To power this flow, there is a membrane lesion gradient from growth cone to cell body that could draw the membrane over the axon at that rate. Further, when an artificial flow is induced to the center of the axon by use of laser tweezers, the primary source of the membrane is from the growth cone. We suggest that during neuron growth, there is excess membrane added at the growth cone in chick dorsal ganglia (DRGs) that undergoes edcocytosis at the cell body, thereby creating a flow that can rapidly alter the content of the axon membrane.

Geometrical Determinants of Neuronal Actin Waves

“…Indeed, we observed that poly-lysine functionalized polystyrene beads attached to the neurite membrane were systematically transported in retrograde fashion to the soma (data not shown). Such an observation was already reported in DRG neurons, and attributed to plasma membrane flow due to differential membrane tension between the growth cone and the soma (Dai and Sheetz, 1995). How this retrograde flow would be connected to the anterograde transport provided by actin waves and would contribute to build membrane tension is an exciting question that we hope will motivate further studies.…”

Asymmetric formation of coated pits on dorsal and ventral surfaces at the leading edges of motile cells and on protrusions of immobile cells

“…, 2001). Membrane deposition at the leading edge is supported, however, by observations that lipid-attached beads moved along the extracellular surfaces of axons from the growth cones to the cell bodies of growing neurons (Dai and Sheetz, 1995). …”

Postsynaptic signaling during plasticity of dendritic spines

“…This may be done by diffusion of excess membrane from the dendrite [45] or exocytosis of endosomes [9]. Ultrastructural studies have shown that some spines contain a relatively large fraction of internal membrane in endosomes [9].…”