Localization of a Guanylyl Cyclase to Chemosensory Cilia Requires the Novel Ciliary MYND Domain Protein DAF-25

Abstract

In harsh conditions, Caenorhabditis elegans arrests development to enter a non-aging, resistant diapause state called the dauer larva. Olfactory sensation modulates the TGF-β and insulin signaling pathways to control this developmental decision. Four mutant alleles of daf-25 (abnormal DAuer Formation) were isolated from screens for mutants exhibiting constitutive dauer formation and found to be defective in olfaction. The daf-25 dauer phenotype is suppressed by daf-10/IFT122 mutations (which disrupt ciliogenesis), but not by daf-6/PTCHD3 mutations (which prevent environmental exposure of sensory cilia), implying that DAF-25 functions in the cilia themselves. daf-25 encodes the C. elegans ortholog of mammalian Ankmy2, a MYND domain protein of unknown function. Disruption of DAF-25, which localizes to sensory cilia, produces no apparent cilia structure anomalies, as determined by light and electron microscopy. Hinting at its potential function, the dauer phenotype, epistatic order, and expression profile of daf-25 are similar to daf-11, which encodes a cilium-localized guanylyl cyclase. Indeed, we demonstrate that DAF-25 is required for proper DAF-11 ciliary localization. Furthermore, the functional interaction is evolutionarily conserved, as mouse Ankmy2 interacts with guanylyl cyclase GC1 from ciliary photoreceptors. The interaction may be specific because daf-25 mutants have normally-localized OSM-9/TRPV4, TAX-4/CNGA1, CHE-2/IFT80, CHE-11/IFT140, CHE-13/IFT57, BBS-8, OSM-5/IFT88, and XBX-1/D2LIC in the cilia. Intraflagellar transport (IFT) (required to build cilia) is not defective in daf-25 mutants, although the ciliary localization of DAF-25 itself is influenced in che-11 mutants, which are defective in retrograde IFT. In summary, we have discovered a novel ciliary protein that plays an important role in cGMP signaling by localizing a guanylyl cyclase to the sensory organelle.

Role of the ANKMY2-FKBP38 Axis in Regulation of the Sonic Hedgehog (Shh) Signaling Pathway

“…The mechanisms by which ANKMY2 enhances Shh signaling and by which FKBP38 antagonizes this action of ANKMY2 remain unclear, however. ANKMY2 localizes to cilia and contributes to the intraflagellar transport-independent translocation of guanylyl cyclase in C. elegans (35,36). We confirmed the interaction between ANKMY2 and guanylyl cyclase in mammalian cells (data not shown).…”

“…9A). Whereas ANKMY2 was previously shown to localize to cilia in C. elegans (35,36), we found that EGFP-ANKMY2 was distributed throughout the cytoplasm of MEFs, with no apparent localization to cilia (Fig. 9B).…”

“…ANKMY2 localizes to sensory cilia in Caenorhabditis elegans, with such localization being required for the proper ciliary localization of guanylyl cyclase (35,36). Given that primary cilia are essential for signal transduction by the vertebrate Shh pathway (8, 9), we examined whether ANKMY2 functions as a regulator of Shh signaling in MEFs.…”

Cell- and subunit-specific mechanisms of CNG channel ciliary trafficking and localization inC. elegans

“…DAF-25 was recently shown to be required to target receptor guanylyl cyclases to sensory cilia in C. elegans (Fujiwara et al, 2010;Jensen et al, 2010), suggesting a possible role in localizing cGMP signaling cascade components. We found that in AWB, TAX-4::GFP localization was unaffected, whereas TAX-2::GFP expression was either lost or restricted to the cell bodies ( Table 2).…”

Ciliopathy proteins establish a bipartite signaling compartment in aC. elegansthermosensory neuron

“…However, there is no evidence for transition zone protein involvement in cGMP signaling. So far, Caenorhabditis elegans DAF-25 (also termed CHB-3; ortholog of mammalian Ankmy2) is the only ciliary protein specifically associated with cGMP signaling (Fujiwara et al, 2010;Jensen et al, 2010). Disrupting DAF-25 results in the failure of two different guanylyl cyclase proteins to target to cilia in sensory neurons.…”