title: Huntingtin coordinates the dynein-mediated dynamic positioning of endosomes and lysosomes.
abstract: Huntingtin (Htt) is a membrane-associated scaffolding protein that interacts with microtubule motors as well as actin-associated adaptor molecules. We examined a role for Htt in the dynein-mediated intracellular trafficking of endosomes and lysosomes. In HeLa cells depleted of either Htt or dynein, early, recycling, and late endosomes (LE)/lysosomes all become dispersed. Despite altered organelle localization, kinetic assays indicate only minor defects in intracellular trafficking. Expression of full-length Htt is required to restore organelle localization in Htt-depleted cells, supporting a role for Htt as a scaffold that promotes functional interactions along its length. In dynein-depleted cells, LE/lysosomes accumulate in tight patches near the cortex, apparently enmeshed by cortactin-positive actin filaments; Latrunculin B-treatment disperses these patches. Peripheral LE/lysosomes in dynein-depleted cells no longer colocalize with microtubules. Htt may be required for this off-loading, as the loss of microtubule association is not seen in Htt-depleted cells or in cells depleted of both dynein and Htt. Inhibition of kinesin-1 relocalizes peripheral LE/lysosomes induced by Htt depletion but not by dynein depletion, consistent with their detachment from microtubules upon dynein knockdown. Together, these data support a model of Htt as a facilitator of dynein-mediated trafficking that may regulate the cytoskeletal association of dynamic organelles.
authors.affiliation: Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Juliane P
authors.initials: JP
authors.lastname: Caviston
authors.forename: Allison L
authors.initials: AL
authors.lastname: Zajac
authors.forename: Mariko
authors.initials: M
authors.lastname: Tokito
authors.forename: Erika L F
authors.initials: EL
authors.lastname: Holzbaur
mesh_terms: D000199:Actins / Q000378:metabolism; D045744:Cell Line, Tumor; D003599:Cytoskeleton / Q000378:metabolism*; D004398:Dyneins / Q000235:genetics* / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism*; D055785:Gene Knockdown Techniques / Q000379:methods; D006367:HeLa Cells; D006801:Humans; D000071058:Huntingtin Protein; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism / Q000502:physiology; D008870:Microtubules / Q000378:metabolism / Q000502:physiology; D020409:Molecular Motor Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D015388:Organelles / Q000378:metabolism; D058105:Polymerization; D021381:Protein Transport / Q000502:physiology; D034622:RNA Interference
chemical_list: D000199:Actins; C086055:HTT protein, human; D000071058:Huntingtin Protein; D051907:Lysosomal Membrane Proteins; D008869:Microtubule-Associated Proteins; D020409:Molecular Motor Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D004398:Dyneins