Bidirectional Translocation of Neurofilaments along Microtubules Mediated in Part by Dynein/Dynactin

Abstract

Neuronal cytoskeletal elements such as neurofilaments, F-actin, and microtubules are actively translocated by an as yet unidentified mechanism. This report describes a novel interaction between neurofilaments and microtubule motor proteins that mediates the translocation of neurofilaments along microtubules in vitro. Native neurofilaments purified from spinal cord are transported along microtubules at rates of 100-1000 nm/s to both plus and minus ends. This motion requires ATP and is partially inhibited by vanadate, consistent with the activity of neurofilament-bound molecular motors. Motility is in part mediated by the dynein/dynactin motor complex and several kinesin-like proteins. This reconstituted motile system suggests how slow net movement of cytoskeletal polymers may be achieved by alternating activities of fast microtubule motors.

Neurofilament Transport Is Dependent on Actin and Myosin

“…Retrograde NF transport also is observed (Yabe et al, 1999;Roy et al, 2000;Wang et al, 2000), which is consistent with the interaction of NFs with a dynein-like motor (for review, see Brady, 2000;Shea and Flanagan, 2001). In this regard, dynein transports NFs along microtubules under cell-free conditions (Shah et al, 2000). The ability of fast axonal transport motors such as kinesin and dynein to translocate NF subunits despite their overall translocation at a rate consistent with slow transport (Nixon, 1992(Nixon, , 1998Hirokawa, 1993;Galbraith and Gallant, 2000;Shea, 2000) is explained by the observation that NFs undergo short bursts of rapid transport that are interrupted by prolonged pauses (Roy et al, 2000;Wang et al, 2000;Ackerley et al, 2003).…”

“…Although NFs undergo predominantly anterograde axonal transport (for review, see Shea and Yabe, 2000), many studies in culture and in situ also demonstrate that some NFs undergo retrograde subunit transport (Glass and Griffin, 1991;Watson et al, 1993;Koehnle and Brown, 1999;Yabe et al, 1999Yabe et al, , 2001aRoy et al, 2000;Shah et al, 2000;Wang et al, 2000). Retrograde NF transport may be mediated by the retrograde motor dynein (Shah et al, 2000).…”

“…Retrograde NF transport may be mediated by the retrograde motor dynein (Shah et al, 2000). In addition to mediating retrograde transport of Figure 11.…”

“…Any NF subunits associated with such moving microtubules therefore also would be propelled in an anterograde direction by dynein-mediated microtubule transport (Susalka and Pfister, 2000). Association of NFs with microtubules, including such moving microtubules, could be mediated either by direct association (Miyasaka et al, 1993;Shah et al, 2000) or linkage via additional microtubule motor proteins (Liao and Gundersen, 1998;Shah et al, 2000), other microtubule-associated proteins (Miyata et al, 1986;Hirokawa et al, 1988), and/or NF-associated proteins such as plectins (Nixon, 1998;Yang et al, 1999;Herrmann and Aebi, 2000). Notably, this line of reasoning encompasses the concept that kinesin may serve to link NF subunits with microtubules (Liao and Gundersen, 1998) in addition to (or instead of) actively translocating microtubules (Yabe et al, 1999.…”

A Role for Intermediate Filaments in Determining and Maintaining the Shape of Nerve Cells

“…With respect to motility, it has been demonstrated that peripherin and NF containing short filaments (or squiggles) move along MT tracks at rates up to 1-2 m/s in association with the molecular motors, kinesin, and cytoplasmic dynein (Yabe et al, 1999(Yabe et al, , 2000Prahlad et al, 2000;Shah et al, 2000;Wang et al, 2000;Helfand et al, 2002Helfand et al, , 2003. From these observations, it seems that the mechanisms governing the intracellular transport of short NF and peripherin squiggles are not fundamentally different from each other.…”