title: Mycalolide B dissociates dynactin and abolishes retrograde axonal transport of dense-core vesicles.
abstract: Axonal transport is critical for maintaining synaptic transmission. Of interest, anterograde and retrograde axonal transport appear to be interdependent, as perturbing one directional motor often impairs movement in the opposite direction. Here live imaging of Drosophila and hippocampal neuron dense-core vesicles (DCVs) containing a neuropeptide or brain-derived neurotrophic factor shows that the F-actin depolymerizing macrolide toxin mycalolide B (MB) rapidly and selectively abolishes retrograde, but not anterograde, transport in the axon and the nerve terminal. Latrunculin A does not mimic MB, demonstrating that F-actin depolymerization is not responsible for unidirectional transport inhibition. Given that dynactin initiates retrograde transport and that amino acid sequences implicated in macrolide toxin binding are found in the dynactin component actin-related protein 1, we examined dynactin integrity. Remarkably, cell extract and purified protein experiments show that MB induces disassembly of the dynactin complex. Thus imaging selective retrograde transport inhibition led to the discovery of a small-molecule dynactin disruptor. The rapid unidirectional inhibition by MB suggests that dynactin is absolutely required for retrograde DCV transport but does not directly facilitate ongoing anterograde DCV transport in the axon or nerve terminal. More generally, MB's effects bolster the conclusion that anterograde and retrograde axonal transport are not necessarily interdependent.
authors.affiliation: Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Samantha L
authors.initials: SL
authors.lastname: Cavolo
authors.affiliation: Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Chaoming
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, MD 21218.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Ketcham
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Suzuki
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
authors.forename: Kresimir
authors.initials: K
authors.lastname: Ukalovic
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Silverman
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, MD 21218.
authors.forename: Trina A
authors.initials: TA
authors.lastname: Schroer
authors.affiliation: Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261 elevitan@pitt.edu.
authors.forename: Edwin S
authors.initials: ES
authors.lastname: Levitan
mesh_terms: D000199:Actins / Q000187:drug effects; D000818:Animals; D001370:Axonal Transport / Q000187:drug effects*; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism; D004330:Drosophila / Q000187:drug effects; D029721:Drosophila Proteins; D000072159:Dynactin Complex; D005260:Female; D008297:Male; D008387:Marine Toxins; D008869:Microtubule-Associated Proteins / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D010080:Oxazoles / Q000494:pharmacology*; D055503:Protein Multimerization; D051381:Rats; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000199:Actins; D019208:Brain-Derived Neurotrophic Factor; D029721:Drosophila Proteins; D000072159:Dynactin Complex; D008387:Marine Toxins; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D010080:Oxazoles; C080978:mycalolide B