Differential roles of kinesin and dynein in translocation of neurofilaments into axonal neurites

Abstract

SummaryNeurofilament (NF) subunits translocate within axons as short NFs, non-filamentous punctate structures ('puncta') and diffuse material that might comprise individual subunits and/or oligomers. Transport of NFs into and along axons is mediated by the microtubule (MT) motor proteins kinesin and dynein. Despite being characterized as a retrograde motor, dynein nevertheless participates in anterograde NF transport through associating with long MTs or the actin cortex through its cargo domain; relatively shorter MTs associated with the motor domain are then propelled in an anterograde direction, along with any linked NFs. Here, we show that inhibition of dynein function, through dynamitin overexpression or intracellular delivery of anti-dynein antibody, selectively reduced delivery of GFPtagged short NFs into the axonal hillock, with a corresponding increase in the delivery of puncta, suggesting that dynein selectively delivered short NFs into axonal neurites. Nocodazole-mediated depletion of short MTs had the same effect. By contrast, intracellular delivery of anti-kinesin antibody inhibited anterograde transport of short NFs and puncta to an equal extent. These findings suggest that anterograde axonal transport of linear NFs is more dependent upon association with translocating MTs (which are themselves translocated by dynein) than is transport of NF puncta or oligomers.

Post-translational modifications of intermediate filament proteins: mechanisms and functions

“…However, ablation of the NF-H C-terminal tail in mice did not alter axonal transport speed 54 , although this might be explained by a compensatory increase in NF-M phosphorylation 51 . Nevertheless, the current model suggests that NF phosphorylation slows the speed of axonal transport 10,51,55 , possibly by promoting NF bundling, which, in turn, competes with kinesin-mediated NF-MT association 55–57 . Determining which kinases phosphorylate which sites in vivo may provide further insight into the significance of NF tail phosphorylation.…”

Anterograde transport blockade precedes deficits in retrograde transport in the visual projection of the DBA/2J mouse model of glaucoma

“…These changes can often affect very specific parts of transport such as different compartments of the axon or the direction of cargo movement away from the cell body or toward the cell body (Shea and Beaty, 2007). Due to the complexity of the nervous system, most of the evidence reporting differential transport effects in pathology are ex vivo (see for example, Brady et al, 1990; Morfini et al, 2007; Motil et al, 2007; Lee et al, 2011; LaPointe et al, 2013). …”

Intermediate filament dynamics: What we can see now and why it matters

“…Imaging of GFP‐tagged NF has demonstrated that NF are transported in axons, moving through NF‐free gaps , or into photo‐bleached segments , though NF also are transported in other forms (NF precursors) . As in the case of vimentin squiggles and particles, transport of NF is dependent on microtubules and requires the microtubule‐motors kinesin (in particular, Kif5A) and dynein . NF also associate with actin and myosin .…”