Abstract
Intraflagellar transport (IFT)1 is important in the formation and maintenance of many cilia, such as the motile cilia that drive the swimming of cells and embryos2, the nodal cilia that generate left-right asymmetry in vertebrate embryos3, and the sensory cilia that detect sensory stimuli in some animals4. The heterotrimeric kinesin-II motor protein drives the anterograde transport of macromolecular complexes, called rafts, along microtubule tracks from the base of the cilium to its distal tip5, whereas cytoplasmic dynein moves the rafts back in the retrograde direction6. We have used fluorescence microscopy to visualize for the first time the intracellular transport of a motor and its cargo in vivo. We observed the anterograde movement of green fluorescent protein (GFP)-labelled kinesin-II motors and IFT rafts within sensory cilia on chemosensory neurons in living Caenorhabditis elegans.
Main
The anterograde IFT motor, hetero-trimeric kinesin-II7, consists of two hetero-dimerized kinesin-related motor subunits and one accessory subunit (KAP)8. To observe kinesin-II-driven IFT within chemosensory cilia, we used transgenic lines of C. elegans expressing GFP fused to the kinesin-II KAP and to a presumptive cargo molecule, OSM-6, a component of IFT rafts that has an essential role in chemosensory ciliary function5,9.
With a fluorescence microscope, we observed that KAP::GFP and OSM-6::GFP polypeptides accumulate in the region of the transition zone at the base of the sensory cilia. This is consistent with previous immunofluorescence data on IFT motors and raft polypeptides in other systems5 (Fig. 1). We observed small fluorescent dots corresponding to the kinesin-II KAP and the OSM-6 cargo emerging from these regions and moving out towards the distal tip of the sensory cilia. Both the motor and its presumptive cargo moved anterogradely at identical rates (0.65±0.11 μm s-1 (n =50) for the KAP compared with 0.65±0.10 μm s-1 (n =50) for OSM-6), which is similar to the velocity of microtubule motility driven by purified heterotrimeric kinesin-II in a motility assay7. In contrast, the sensory ciliary transmembrane receptor ODR-10 moved at a faster rate (1.59±0.28 μm s-1 (n =10), confirming that the identical velocities displayed by KAP::GFP and OSM-6::GFP are not an artefact of the recording technique.
This direct viewing of the intracellular transport of a motor and its cargo in vivo provides strong support for the hypothesis that heterotrimeric kinesin-II is the motor protein that drives anterograde IFT5. In chemosensory neurons of C. elegans, it is likely that kinesin-II-driven IFT delivers structural components of sensory ciliary axonemes and components of the sensory signalling machinery that are concentrated in these cilia.
Genetic studies have identified 25 genes, including osm-6, that are essential for cili-ary function in this system10, and the ability to view IFT in organisms carrying mutations in these genes will make it possible to determine which of the corresponding gene products are linked to the kinesin-II transport pathway. In a broader context, our approach should allow the direct observation of motor and cargo molecules participating in IFT in a broad range of cilia and flagella.
References
Rosenbaum, J. L., Cole, D. G. & Diener, D. J. Cell Biol. 144, 385–388 (1999).
Morris, R. L. & Scholey, J. M. J. Cell Biol. 138, 1009–1022 (1997).
Nonaka, S. et al. Cell 95, 829–837 (1998).
Perkins, L. A., Hedgecock, E. M., Thompson, J. N. & Culotti, J. G. Dev. Biol. 117, 456–487 (1986).
Cole, D. G. et al. J. Cell Biol. 141, 993–1008 (1998).
Pazour, G. J., Wilkerson, C. G. & Witman, G. B. J. Cell Biol. 141, 979–992 (1998).
Cole, D. G. et al. Nature 366, 268–270 (1993).
Signor, D., Wedaman, K. P., Rose, L. S. & Scholey, J. M. Mol. Biol. Cell 10, 345–360 (1999).
Collet, J., Spike, C. A., Lundquist, E. A., Shaw, J. E. & Herman, R. K. Genetics 148, 187–200 (1998).
Starich, T. A. et al. Genetics 139, 171–188 (1995).
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Orozco, J., Wedaman, K., Signor, D. et al. Movement of motor and cargo along cilia. Nature 398, 674 (1999). https://doi.org/10.1038/19448
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DOI: https://doi.org/10.1038/19448
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