Huntingtin coordinates the dynein-mediated dynamic positioning of endosomes and lysosomes

JP Caviston, AL Zajac, M Tokito… - Molecular biology of the …, 2011 - Am Soc Cell Biol
Molecular biology of the cell, 2011Am Soc Cell Biol
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 …
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.
Am Soc Cell Biol