Center for Cellular Neurobiology and Neurodegeneration Research, Department of Biological Sciences, University of Massachusetts, One University Avenue, Lowell, MA 01854, USA.
J Cell Sci. 2011 Apr 1;124(Pt 7):1022-31. doi: 10.1242/jcs.079046. Epub 2011 Mar 1.
Neurofilament (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 GFP-tagged 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.
神经丝（NF）亚基在轴突中作为短 NF、无丝状点状结构（“点状”）和弥散物质移位，这些物质可能包含单个亚基和/或寡聚物。NF 向轴突内和沿轴突的运输由微管（MT）马达蛋白驱动蛋白和动力蛋白介导。尽管被表征为逆行马达，但动力蛋白通过与长 MT 或通过其货物结构域与肌动球蛋白皮层结合，仍然参与正向 NF 运输；与马达结构域相关的相对较短的 MT 随后被向前推进，与任何连接的 NF 一起。在这里，我们表明，通过 dynamitin 过表达或抗动力蛋白抗体的细胞内递送抑制动力蛋白功能，选择性地减少 GFP 标记的短 NF 进入轴丘的递呈，同时点状物质的递呈增加，表明动力蛋白选择性地将短 NF 递呈到轴突神经突中。微管蛋白解聚剂介导的短 MT 的耗竭也有同样的效果。相比之下，细胞内递送抗驱动蛋白抗体同样抑制短 NF 和点状物质的正向运输。这些发现表明，线性 NF 的正向轴突运输更依赖于与转运 MT 的结合（这些 MT 本身由动力蛋白转运），而不是 NF 点状物质或寡聚物的运输。
