Axonal Transport of Synaptic Vesicles and Muscarinic Receptors: Effect of Protein Synthesis Inhibitors

Abstract

The effect of cycloheximide, a protein synthesis inhibitor, was studied on the axonal transport of noradrenergic synaptic vesicles and presynaptic muscarinic receptors, identified by in vitro binding of [3H]dihydrotetrabenazine and [3H]quinuclidinylbenzilate, respectively, in rat sciatic nerve. Cycloheximide (1.5 mg/kg) administered subcutaneously 2 h before ligation decreased by approximately 50% the accumulation of vesicles and receptors in the proximal segment above the ligature placed on the nerve; its action was detectable after a lag period of 10 h and disappeared 96 h after administration. Double ligatures were placed on the nerve at various time intervals between the first (distal) and the second (proximal) ligature, and the accumulation of vesicles and receptors proximal to the second ligature was measured; the first ligature diminished the accumulation above the second ligature. At an interval of 96 h between the first and the second ligature, cycloheximide completely prevented the accumulation of vesicles and receptors proximal to the second ligature. The effects of double ligatures and the response to cycloheximide treatment can best be explained on the assumption that an important proportion of synaptic vesicles and presynaptic receptors is being recycled in the nerve cell bodies after retrograde transport.

Ultrastructural and electrophysiological changes associated with K+-evoked release of neurotransmitter at the synaptic terminals of skate photoreceptors

“…cles and their content are maintained at relatively constant levels by the rapid endocytotic retrieval of membrane and the intracellular traffic of membranes, proteins and other essentials from the cell body to its terminal (Krygier-Brevart et al, 1974;Levy et al, 1990). But despite the high rates of vesicle retrieval and transmitter biosynthesis, these events cannot always keep pace with stimulation-induced discharge processes.…”

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

“…A similar dissociation of protein synthesis from transport organelle biogenesis may be deduced from the work of Goldberg et al (1978; see Table 1) on individual neurons of Aplysia californica. A concentration of anisomycin that reduced protein synthesis by more than 95% within 5 min had no effect on the soma-to-axon export of [3H]serotonin, a marker of serotonin storage granules, for up to 5 h. The results of Levy et al ( 1990) also provide evidence for continued release of organelles into axons when protein synthesis is inhibited.…”

Synapse integrity and function: Dependence on protein synthesis and identification of potential failure points

“…In this study we used protein synthesis inhibitors to block the supply of new proteins in neurons. Translational inhibitors, however, have been reported to have widespread effects on neuronal function, some of which might be unrelated to their capacity to suppress protein synthesis: Superinduction of immediate early genes ( Mahadevan and Edwards, 1991 ; Hazzalin et al, 1998 ; Radulovic and Tronson, 2008 ; Santos et al, 2019 ); increased synthesis /hyperproduction of specific proteins ( Törocsik and Szeberényi, 2000a ; Radulovic and Tronson, 2008 ; Kenney et al, 2016 ); activation of signaling pathways ( Cano et al, 1994 ; Kardalinou et al, 1994 ; Zinck et al, 1995 ; Iordanov et al, 1997 ; Hazzalin et al, 1998 ; Iordanov and Magun, 1998 ; Törocsik and Szeberényi, 2000a ; Monaghan et al, 2014 ; Tyssowski et al, 2018 ); apoptosis/cytotoxicity (in certain cell types; Törocsik and Szeberényi, 2000b ; Monaghan et al, 2014 ; Chan et al, 2017 ); effects on protein degradation ( Franklin and Johnson, 1998 ; Dai et al, 2013 ; see also Ding et al, 2007 ; Kaang and Choi, 2012 ; Jarome and Helmstetter, 2014 ); and altered axonal transport ( Levy et al, 1990 ). Despite these reports, the similarity of the findings in experiments based on two different inhibitors (CHX, ANI) suggest that these are unlikely to stem primarily from off-target effects of these inhibitors.…”