Myosin Va and microtubule-based motors are required for fast axonal retrograde transport of tetanus toxin in motor neurons.
Using a novel assay based on the sorting and transport of a fluorescent fragment of tetanus toxin, we have investigated the cytoskeletal and motor requirements of axonal retrograde transport in living mammalian motor neurons. This essential process ensures the movement of neurotrophins and organelles from the periphery to the cell body and is crucial for neuronal survival. Unlike what is observed in sympathetic neurons, fast retrograde transport in motor neurons requires not only intact microtubules, but also actin microfilaments. Here, we show that the movement of tetanus toxin-containing carriers relies on the nonredundant activities of dynein as well as kinesin family members. Quantitative kinetic analysis indicates a role for dynein as the main motor of these carriers. Moreover, this approach suggests the involvement of myosin(s) in retrograde movement. Immunofluorescence screening with isoform-specific myosin antibodies reveals colocalization of tetanus toxin-containing retrograde carriers with myosin Va. Motor neurons from homozygous myosin Va null mice showed slower retrograde transport compared with wild-type cells, establishing a unique role for myosin Va in this process. On the basis of our findings, we propose that coordination of myosin Va and microtubule-dependent motors is required for fast axonal retrograde transport in motor neurons.
Molecular NeuroPathoBiology Laboratory, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, UK.
Giovanna
G
Lalli
Stephen
S
Gschmeissner
Giampietro
G
Schiavo
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D004398:Dyneins / Q000502:physiology; D016547:Kinesins / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism; D020409:Molecular Motor Proteins / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000502:physiology*; D024701:Myosin Type V / Q000502:physiology*; D015388:Organelles / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D013744:Tetanus Toxin / Q000378:metabolism
D000199:Actins; D020409:Molecular Motor Proteins; C513082:Myo5a protein, mouse; C513081:Myo5a protein, rat; D020033:Protein Isoforms; D013744:Tetanus Toxin; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D004398:Dyneins; D016547:Kinesins