Comparison of nerve terminal events in vivo effecting retrograde transport of vesicles containing neurotrophins or synaptic vesicle components

Abstract

Although vesicular retrograde transport of neurotrophins in vivo is well established, relatively little is known about the mechanisms that underlie vesicle endocytosis and formation before transport. We demonstrate that in vivo not all retrograde transport vesicles are alike, nor are they all formed using identical mechanisms. As characterized by density, there are at least two populations of vesicles present in the synaptic terminal that are retrogradely transported along the axon: those containing neurotrophins (NTs) and those resulting from synaptic vesicle recycling. Vesicles containing nerve growth factor (NGF), NT-3, or NT-4 had similar densities with peak values at about 1.05 g/ml. Synaptic-derived vesicles, labeled with anti-dopamine beta-hydroxylase (DBH), had densities with peak values at about 1.16 g/ml. We assayed the effects of pharmacologic agents in vivo on retrograde transport from the anterior eye chamber to the superior cervical ganglion. Inhibitors of phosphatidylinositol-3-OH (PI-3) kinase and actin function blocked transport of both anti-DBH and NGF, demonstrating an essential role for these molecules in retrograde transport of both vesicle types. Dynamin, a key element in synaptic vesicle recycling, was axonally transported in retrograde and anterograde directions, and compounds able to interfere with dynamin function had a differential effect on retrograde transport of NTs and anti-DBH. Okadaic acid significantly decreased retrograde axonal transport of anti-DBH and increased NGF retrograde transport. We conclude that there are both different and common proteins involved in endocytosis and targeting of retrograde transport of these two populations of vesicles.

High‐Resolution Fractionation of Signaling Endosomes Containing Different Receptors

“…The data are more simply represented by a contour plot similar to a topographic map in which the intensity of shading indicates the height of the protein peak (Figure 1D). Neurotrophin‐labeled endosomes from cultured rat (E13.5) dorsal root ganglia (DRG) neurons have similar densities to endosomes from PC12 cells (unpublished observations) as do organelles isolated directly from axons containing retrogradely transported neurotrophins (53), suggesting that PC12 cells are a suitable model for the study of neuronal membrane traffic.…”

Synapsin II and calcium regulate vesicle docking and the cross‐talk between vesicle pools at the mouse motor terminals

“…Since we observe alterations in the total vesicle number in the terminal, we consider the nerve terminal as an open system, where total vesicle number is controlled by axonal transport, as well as spontaneous exo‐ and endocytosis. The axonal vesicle transport is actin dependent (Weible et al 2004; Brown et al 2004) and involves vesicle clusters (Kraszewski et al 1995), and thus it is likely that the axonal transport would affect directly actin/synapsin bound vesicles from the pool S . We incorporated in the model fast, local endocytosis, a process by which vesicles locally turn over and enter the releasable pool R ; in addition, the model includes slow endocytosis, a process by which vesicles are uptaken and incorporated into the intermediate pool, I .…”

A Novel Population of α-Smooth Muscle Actin-Positive Cells Activated in a Rat Model of Stroke: An Analysis of the Spatio-Temporal Distribution in Response to Ischemia

“…It is possible that neurons that send axons along the corpus callosum, the proposed route of migration for the pericyte precursors to the peri-infarct, provide the stimulus for these events of pericyte proliferation and migration. Such stimuli might arise from the relatively slow mechanisms of retrograde transport that have been described for damaged neurons (Hendry et al, 1995;Johanson et al, 1995;Weible et al, 2004).…”