title: Direct observation demonstrates that Liprin-alpha is required for trafficking of synaptic vesicles.
abstract: Axonal transport is required for the elaboration and maintenance of synaptic morphology and function. Liprin-alphas are scaffolding proteins important for synapse structure and electrophysiology. A reported interaction with Kinesin-3 (Kif1a) suggested Liprin-alpha may also be involved in axonal transport. Here, at the light and ultrastructural levels, we discover aberrant accumulations of synaptic vesicle markers (Synaptotagmin and Synaptobrevin-GFP) and clear-core vesicles along Drosophila Liprin-alpha mutant axons. Analysis of presynaptic markers reveals reduced levels at Liprin-alpha synapses. Direct visualization of Synaptobrevin-GFP transport in living animals demonstrates a decrease in anterograde processivity in Liprin-alpha mutants but also an increase in retrograde transport initiation. Pull-down assays reveal that Liprin-alpha interacts with Drosophila Kinesin-1 (Khc) but not dynein. Together, these findings suggest that Liprin-alpha promotes the delivery of synaptic material by a direct increase in kinesin processivity and an indirect suppression of dynein activation. This work is the first to use live observation in Drosophila mutants to demonstrate the role of a scaffolding protein in the regulation of bidirectional transport. It suggests the synaptic strength and morphology defects linked to Liprin-alpha may in part be due to a failure in the delivery of synaptic-vesicle precursors.
authors.affiliation: Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Kyle E
authors.initials: KE
authors.lastname: Miller
authors.forename: Jamin
authors.initials: J
authors.lastname: DeProto
authors.forename: Nancy
authors.initials: N
authors.lastname: Kaufmann
authors.forename: Bharatkumar N
authors.initials: BN
authors.lastname: Patel
authors.forename: April
authors.initials: A
authors.lastname: Duckworth
authors.forename: David
authors.initials: D
authors.lastname: Van Vactor
mesh_terms: D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D002135:Calcium-Binding Proteins; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster; D005982:Glutathione Transferase; D049452:Green Fluorescent Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016547:Kinesins / Q000378:metabolism; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D050683:R-SNARE Proteins; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure; D013572:Synaptic Vesicles / Q000378:metabolism*; D050857:Synaptotagmins
chemical_list: D002135:Calcium-Binding Proteins; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; C490600:Liprin-alpha protein, Drosophila; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D050683:R-SNARE Proteins; D050857:Synaptotagmins; D049452:Green Fluorescent Proteins; D005982:Glutathione Transferase; D016547:Kinesins