Role of a Class Dhc1b Dynein in Retrograde Transport of Ift Motors and Ift Raft Particles along Cilia, but Not Dendrites, in Chemosensory Neurons of Living Caenorhabditis elegans

Abstract

The heterotrimeric motor protein, kinesin-II, and its presumptive cargo, can be observed moving anterogradely at 0.7 μm/s by intraflagellar transport (IFT) within sensory cilia of chemosensory neurons of living Caenorhabditis elegans, using a fluorescence microscope–based transport assay (Orozco, J.T., K.P. Wedaman, D. Signor, H. Brown, L. Rose, and J.M. Scholey. 1999. Nature. 398:674). Here, we report that kinesin-II, and two of its presumptive cargo molecules, OSM-1 and OSM-6, all move at ∼1.1 μm/s in the retrograde direction along cilia and dendrites, which is consistent with the hypothesis that these proteins are retrieved from the distal endings of the cilia by a retrograde transport pathway that moves them along cilia and then dendrites, back to the neuronal cell body. To test the hypothesis that the minus end–directed microtubule motor protein, cytoplasmic dynein, drives this retrograde transport pathway, we visualized movement of kinesin-II and its cargo along dendrites and cilia in a che-3 cytoplasmic dynein mutant background, and observed an inhibition of retrograde transport in cilia but not in dendrites. In contrast, anterograde IFT proceeds normally in che-3 mutants. Thus, we propose that the class DHC1b cytoplasmic dynein, CHE-3, is specifically responsible for the retrograde transport of the anterograde motor, kinesin-II, and its cargo within sensory cilia, but not within dendrites.

IFT‐81 and IFT‐74 are required for intraflagellar transport in C. elegans

“…Here, we used a model organism, C. elegans. In C. elegans, 60 of the 302 neurons of the hermaphrodite are ciliated sensory neurons, and several works have demonstrated that the mutants of IFT-related genes show defects in sensory functions (Cole et al 1998;Signor et al 1999;Qin et al 2001;Haycraft et al 2003;Schafer et al 2003;Blacque et al 2004;Scholey et al 2004;Snow et al 2004;Ou et al 2005;Bell et al 2006;Evans et al 2006). In the present work, we identified nematode IFT-81 and IFT-74, whose C. reinhardtii orthologues were recently shown to form core complex in subcomplex B (Lucker et al 2005), and attempted to elucidate their physiological roles in C. elegans.…”

The Molecular Identities of the Caenorhabditis elegans Intraflagellar Transport Genes dyf-6, daf-10 and osm-1

“…Consistent with an effect on cilia, some of these mutations affect genes that encode counterparts of complex A or B components of the Chlamydomonas IFT (for review, see Cole 2003). Moreover, on the basis of fusions of GFP with OSM-6, OSM-1, DAF-10, and others, IFT has been demonstrated for the cilia of the dendritic endings of the amphids and phasmids in C. elegans Signor et al 1999;Qin et al 2001;Blacque et al 2005;Ou et al 2005a,b).…”

Intraflagellar transport proteins 172, 80, 57, 54, 38, and 20 form a stable tubulin‐binding IFT‐B2 complex

“…IFT in Chlamydomonas reinhardtii is dependent on the heterotrimeric kinesin II motor to transport ciliary cargo from the cell body to the tip of the cilium (anterograde IFT) (Kozminski et al , 1995; Cole et al , 1998; Qin et al , 2004; Hao et al , 2011; Craft et al , 2015), but in C. elegans and most likely also vertebrate cilia the heterotrimeric kinesin II cooperates with a homodimeric kinesin II motor for anterograde transport (Snow et al , 2004; Williams et al , 2014; Prevo et al , 2015). At the ciliary tip, exchange of the cargo and remodeling of the IFT complex take place and dynein 2 transports the IFT complex and recycling products back to the cell body (retrograde IFT) (Pazour et al , 1999; Porter et al , 1999; Signor et al , 1999; Qin et al , 2004). IFT is mediated by the IFT complex containing at least 22 protein subunits (organized into IFT‐A and IFT‐B subcomplexes), which likely mediates the interactions between IFT motors and ciliary cargo (Bhogaraju et al , 2013b).…”