title: JIP3 Activates Kinesin-1 Motility to Promote Axon Elongation.
abstract: Kinesin-1 is a molecular motor responsible for cargo transport along microtubules and plays critical roles in polarized cells, such as neurons. Kinesin-1 can function as a dimer of two kinesin heavy chains (KHC), which harbor the motor domain, or as a tetramer in combination with two accessory light chains (KLC). To ensure proper cargo distribution, kinesin-1 activity is precisely regulated. Both KLC and KHC subunits bind cargoes or regulatory proteins to engage the motor for movement along microtubules. We previously showed that the scaffolding protein JIP3 interacts directly with KHC in addition to its interaction with KLC and positively regulates dimeric KHC motility. Here we determined the stoichiometry of JIP3-KHC complexes and observed approximately four JIP3 molecules binding per KHC dimer. We then determined whether JIP3 activates tetrameric kinesin-1 motility. Using an in vitro motility assay, we show that JIP3 binding to KLC engages kinesin-1 with microtubules and that JIP3 binding to KHC promotes kinesin-1 motility along microtubules. We tested the in vivo relevance of these findings using axon elongation as a model for kinesin-1-dependent cellular function. We demonstrate that JIP3 binding to KHC, but not KLC, is essential for axon elongation in hippocampal neurons as well as axon regeneration in sensory neurons. These findings reveal that JIP3 regulation of kinesin-1 motility is critical for axon elongation and regeneration.
authors.affiliation: Department of Anatomy and Neurobiology, School of Medicine, Washington University, St. Louis, Missouri 63110.
authors.forename: Dana
authors.initials: D
authors.lastname: Watt
authors.affiliation: Department of Biology, Washington University, St. Louis, Missouri 63110.
authors.forename: Ram
authors.initials: R
authors.lastname: Dixit
authors.affiliation: Department of Anatomy and Neurobiology, School of Medicine, Washington University, St. Louis, Missouri 63110. Electronic address: cavalli@pcg.wustl.edu.
authors.forename: Valeria
authors.initials: V
authors.lastname: Cavalli
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000378:metabolism*; D057809:HEK293 Cells; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D016547:Kinesins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008870:Microtubules / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D011984:Sensory Receptor Cells / Q000166:cytology / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C403619:Mapk8ip3 protein, mouse; D046912:Multiprotein Complexes; D009419:Nerve Tissue Proteins; D016547:Kinesins
keywords: JIP3; KHC; axon; kinesin; molecular motor; motility; neurite outgrowth; regeneration