Kinesin-dependent transport of keratin filaments: A unified mechanism for intermediate filament transport

Keratin intermediate filaments (IFs) are the major cytoskeletal component in epithelial cells. The dynamics ofkeratinIFshavebeendescribedtodependmostlyonthe actincytoskeleton,but the rapid transport of fully polymerized keratin filaments has not been reported. In this work, we used a combination of photoconversion experiments and clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeats-associated protein 9 genome editing to study the role ofmicrotubules and microtubulemotors in keratin filament transport. We found that long keratin filaments, like other types of IFs, are transported along microtubules by kinesin-1. Our data revealed that keratin and vimentin are nonconventional kinesin-1 cargoes because their transport did not require kinesin light chains,which are a typical adapter for kinesin-dependent cargo transport. Furthermore, we found that the same domain of the kinesin heavy chain tail is involved in keratin and vimentin IF transport, strongly suggesting that multiple types of IFs move along microtubules using an identical mechanism.