Interplay between kinesin-1 and cortical dynein during axonal outgrowth and microtubule organization in Drosophila neurons

Abstract

In this study, we investigated how microtubule motors organize microtubules in Drosophila neurons. We showed that, during the initial stages of axon outgrowth, microtubules display mixed polarity and minus-end-out microtubules push the tip of the axon, consistent with kinesin-1 driving outgrowth by sliding antiparallel microtubules. At later stages, the microtubule orientation in the axon switches from mixed to uniform polarity with plus-end-out. Dynein knockdown prevents this rearrangement and results in microtubules of mixed orientation in axons and accumulation of microtubule minus-ends at axon tips. Microtubule reorganization requires recruitment of dynein to the actin cortex, as actin depolymerization phenocopies dynein depletion, and direct recruitment of dynein to the membrane bypasses the actin requirement. Our results show that cortical dynein slides ‘minus-end-out’ microtubules from the axon, generating uniform microtubule arrays. We speculate that differences in microtubule orientation between axons and dendrites could be dictated by differential activity of cortical dynein.DOI: http://dx.doi.org/10.7554/eLife.10140.001

Microtubule–microtubule sliding by kinesin-1 is essential for normal cytoplasmic streaming in Drosophila oocytes

“…In contrast to kinesin-1's function in streaming, dynein is not required for fast streaming; instead, it inhibits the shift from slow streaming to fast streaming (8,9). This KHC-dependent and KLC/dynein-independent streaming mechanism highly resembles another important function of KHC, called microtubule-microtubule sliding, studied by our group (10)(11)(12)(13)(14)(15). In this process, KHC binds one microtubule through its ATPindependent C-terminal-binding site while walking on another microtubule using its ATP-dependent motor domain, as reported by Winding et al (17).…”

“…1A) and binds to the acidic E-hook of tubulin through an electrostatic interaction (18,19). Furthermore, we have shown that KHC-driven microtubule sliding is independent of KLC and cannot be inhibited by dynein knockdown or dynein inhibition (10,12,14,15).…”

“…As we have previously shown in tissue culture cells and neurons, sliding occurs between two free microtubules; thus, microtubules move in both directions (10)(11)(12)(13)(14)(15). However, oocyte streaming in stage 10B oocytes is usually unidirectional.…”

“…Cytoskeletal filaments and molecular motors are major players that generate the forces required for these activities. For instance, kinesin-1 and microtubules have been shown to provide the mechanical forces required in multiple cellular contexts, such as organelle transport (1)(2)(3)(4), ooplasmic streaming (5)(6)(7)(8)(9), and process formation (10)(11)(12)(13)(14)(15).…”

The Kinesin Adaptor Calsyntenin-1 Organizes Microtubule Polarity and Regulates Dynamics during Sensory Axon Arbor Development

“…Live imaging in Drosophila neurons showed that MTs display mixed polarity at the initial stage of axon formation from the cell body, but then reorganize to become predominantly plus-end-distal as axons extend (del Castillo et al, 2015). Similarly, in cultured rat hippocampal neurons, immature neurites have mixed MT polarity and plus-end-distal polarity is established once the axon is specified (Kollins et al, 2009; Yau et al, 2016).…”