The dynamics of protein localisation to restricted zones within Drosophila mechanosensory cilia

Abstract

The Drosophila chordotonal neuron cilium is the site of mechanosensory transduction. The cilium has a 9 + 0 axoneme structure and is highly sub-compartmentalised, with proximal and distal zones harbouring different TRP channels and the proximal zone axoneme also being decorated with axonemal dynein motor complexes. The activity of the dynein complexes is essential for mechanotransduction. We investigate the localisation of TRP channels and dynein motor complexes during ciliogenesis. Differences in timing of TRP channel localisation correlate with order of construction of the two ciliary zones. Dynein motor complexes are initially not confined to their target proximal zone, but ectopic complexes beyond the proximal zone are later cleared, perhaps by retrograde transport. Differences in transient distal localisation of outer and inner dynein arm complexes (ODAs and IDAs) are consistent with previous suggestions from unicellular eukaryotes of differences in processivity during intraflagellar transport. Stable localisation depends on the targeting of their docking proteins in the proximal zone. For ODA, we characterise an ODA docking complex (ODA-DC) that is targeted directly to the proximal zone. Interestingly, the subunit composition of the ODA-DC in chordotonal neuron cilia appears to be different from the predicted ODA-DC in Drosophila sperm.

The Small Interactor of PKD2 protein promotes the assembly and ciliary entry of the Chlamydomonas PKD2–mastigoneme complexes

“…Indeed, Lee et al reported partitioning of the ciliary membrane along the length of cilia into actin-dependent corals, transiently confining diffusing G-protein coupled receptors ( Lee et al, 2018 ). Furthermore, the ciliary dilation of chordotonal neuron cilia in Drosophila defines or maintains the border between the proximal and distal zone ( Xiang et al, 2022 ) and, in sperm flagella, the septin-based annulus forms a diffusion barrier between the midpiece and principal piece ( Kwitny et al, 2010 ).…”

“…This implies that PKD2 is redistributed, for example, the proximal border of the distal region must be moved distally as cilia grow, a process that likely involves changes in the underlying axoneme to generate or eliminate PKD2-binding sites. During the assembly of Drosophila auditory cilia, dynein motor complexes are initially not confined to their proximal target zone, and ectopic complexes initially observed in the distal zone, are later removed ( Xiang et al, 2022 ). Also, the OcNC1 channel subunit, initially present in the proximal segment of assembling rat olfactory cilia, is later moved to its final position in the distal segment ( Matsuzaki et al, 1999 ).…”

“…Rather than being homogenous in composition, the ciliary membrane often contains sub-compartments in which specific membrane proteins are concentrated. In the auditory cilia of Drosophila chordotonal neurons, for example, the TRP channel NompC is localized in parts of the distal zone whereas voltage-gated TRPV channels are present in the proximal zone ( Xiang et al, 2022 ). Also in Drosophila , the polycystin 2 (PKD2) ortholog AMO is located near the tip of sperm cilia ( Köttgen et al, 2011 ; Watnick et al, 2003 ).…”

A Drosophila model for Meniere’s disease: Dystrobrevin is required for support cell function in hearing and proprioception

“…The homozygous flies are viable with no apparent defects. For Iav localisation, the iav-GFP line contains a genomic fusion transgene that rescues the null iav mutant ( Gong et al, 2004 ) and has been widely used ( Cachero et al, 2011 ; Newton et al, 2012 ; Xiang et al, 2022 ).…”

“…Whole adult heads of Dyb EY01099 mutant ( n = 3) and yw control ( n = 3) flies were removed and prepared following the protocol described previously ( Xiang et al, 2022 ; zur Lage et al, 2018 ). Sections were examined with a Hitachi 7000 electron microscope, and 124 images were taken.…”