ARL13B regulates Sonic hedgehog signaling from outside primary cilia

Gigante, Eduardo D.; Taylor, Megan R; Ivanova, Anna; Kahn, Richard; Caspary, Tamara

doi:10.7554/elife.50434

Cited by 65 publications

(88 citation statements)

References 82 publications

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“…These results are compatible with the fact that the phenotypes of INPP5E -KO and ARL13B -KO cells closely resemble each other ( Figs 2 and 3 ). In this context, it is important to note the recent study of Gigante et al showing that knockin mice of Arl13b(V358A), which is an Arl13b variant defective in ciliary localization due to a Val-to-Ala substitution in the VxP ciliary targeting motif ( Higginbotham et al, 2012 ), showed apparently normal Hh signaling, even though ciliary localization of INPP5E was not observed ( Gigante et al, 2020 ). Thus, similarly to INPP5E(ΔCTS), the cilia-excluded Arl13b(V358A) variant might be able to enter cilia but unable to be retained on the ciliary membrane, although it is unknown as to how the VxP motif participates in the ciliary targeting of ARL13B.…”

Section: Discussionmentioning

confidence: 99%

Interaction of INPP5E with ARL13B is essential for its ciliary membrane retention but dispensable for its ciliary entry

et al. 2020

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Compositions of proteins and lipids within cilia and on the ciliary membrane are maintained to be distinct from those of the cytoplasm and plasma membrane, respectively, by the presence of the ciliary gate. INPP5E is a phosphoinositide 5-phosphatase that is localized on the ciliary membrane by anchorage via its C-terminal prenyl moiety. In addition, the ciliary membrane localization of INPP5E is determined by the small GTPase ARL13B. However, it remained unclear as to how ARL13B participates in the localization of INPP5E. We here show that wild-type INPP5E, INPP5E(WT), in ARL13B-knockout cells and an INPP5E mutant defective in ARL13B binding, INPP5E(ΔCTS), in control cells were unable to show steady-state localization on the ciliary membrane. However, not only INPP5E(WT) but also INPP5E(ΔCTS) was able to rescue the abnormal localization of ciliary proteins in INPP5E-knockout cells. Analysis using the chemically induced dimerization system demonstrated that INPP5E(WT) in ARL13B-knockout cells and INPP5E(ΔCTS) in control cells were able to enter cilia, but neither was retained on the ciliary membrane due to the lack of the INPP5E–ARL13B interaction. Thus, our data demonstrate that binding of INPP5E to ARL13B is essential for its steady-state localization on the ciliary membrane but is dispensable for its entry into cilia.

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Section: Discussionmentioning

confidence: 99%

Interaction of INPP5E with ARL13B is essential for its ciliary membrane retention but dispensable for its ciliary entry

et al. 2020

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“…Given the ciliary function of Arl13 (see above), we speculate that the DD_RI_PKA domain in some Arl13 proteins interacts with a cilium-localized AKAP, such as the aforementioned RSP3 protein (Gaillard et al, 2001;Jivan et al, 2009). In contrast, mammalian Arl13b contains the simpler VxP motif in the large C-terminal domain that is required for ciliary localization (Higginbotham et al, 2012;Cevik et al, 2013;Gigante et al, 2020). DD_RI_PKA domains in Phytophthora sojae Arl13 are followed by the TUDOR domain, known for the ability to bind to the methylated lysine and/or arginine residues (Botuyan and Mer, 2016).…”

Section: Extensive Diversity Of Multi-domain Arf Family Membersmentioning

confidence: 99%

A eukaryote-wide perspective on the diversity and evolution of the ARF GTPase protein family

Vargová

Wideman

Derelle

et al. 2020

Preprint

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ARF family GTPases act in diverse cellular processes, critical for organellar function today and understanding eukaryotic origins. However, our understanding of ARF family evolution is limited. Our phylogenetically comprehensive in silico analyses of ARF family members here doubles the set of ancestral eukaryotic paralogs and challenges existing norms for small GTPases, with examples of non-standard modes of membrane association and novel protein architectures. Evidence for the pan-eukaryotic and ancestral origin of Arf6, Arl13 and Arl16 is presented for the first time, while three newly described ancient sub-families are absent from well-studied model organisms, leaving their functions completely unexplored. Evolutionary analysis of metazoa-specific ARF family GTPases also uncovered several new proteins in animals. Delving back to eukaryogenesis, the relationship within the ARF GTPases sets boundaries for scenarios of vesicle coat origins. Finally, we report the discovery of the archaeal proteins from which the entire eukaryotic ARF family is derived.

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“…To directly ask whether ARL13B mediates SCP guidance to the dorsal thalamus from within cilia, we examined a mouse expressing a cilia-excluded variant of ARL13B, ARL13B V358A (Figure 2) (Gigante et al 2020). We previously demonstrated that ARL13B V358A retains all known ARL13B biochemical activity, is undetectable in cilia yet transduces vertebrate Hh signaling normally (Mariani et al 2016; Gigante et al 2020). We found that either dorsal or ventral thalamus injections resulted in visible clusters of dye-stained cells in the contralateral DCN in control (Figure 2A-B, dorsal: 3/3; ventral: 5/5) and Arl13b V358A/V358A (Figure 2C-D, dorsal: 3/3; ventral: 3/3) animals.…”

Section: Resultsmentioning

confidence: 99%

“…Note that Arl13b Δ is the deletion allele resulting from germline deletion of the conditional Arl13b flox allele. Genotyping was as previously described (Heydemann et al 2001; Goebbels et al 2006; Nolan-Stevaux et al 2009; Su et al 2012; Gigante et al 2020).…”

Section: Methodsmentioning

confidence: 99%

“…ARL13B does not function from within cilia to mediate SCP guidance ARL13B and the other 35 genes implicated in Joubert syndrome associate with the cilium or centrosome leading to the assumption that protein dysfunction from these locales underlies JSRD phenotypes (Parisi 2019). To directly ask whether ARL13B mediates SCP guidance to the dorsal thalamus from within cilia, we examined a mouse expressing a cilia-excluded variant of ARL13B, ARL13B V358A (Figure 2) (Gigante et al 2020). We previously demonstrated that ARL13B V358A retains all known ARL13B biochemical activity, is undetectable in cilia yet transduces vertebrate Hh signaling normally (Mariani et al 2016;Gigante et al 2020).…”

Section: Arl13b Is Required For Normal Scp Projection To the Dorsal Tmentioning

confidence: 99%

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Smoothened and ARL13B are critical in mouse for superior cerebellar peduncle targeting

Suciu

Long

Caspary

2021

Preprint

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Patients with the ciliopathy Joubert syndrome present with physical anomalies, intellectual disability, and are diagnosed by the hindbrain “molar tooth sign” malformation. This radiological abnormality results from a combination of hypoplasia of the cerebellar vermis and inappropriate targeting of the white matter tracts of the superior cerebellar peduncles, which create a deepened interpeduncular fossa. ARL13B is a cilia-enriched regulatory GTPase established to regulate cell fate, cell proliferation and axon guidance through vertebrate Hedgehog signaling. In patients, point mutations in ARL13B cause Joubert syndrome. In order to understand the etiology of the molar tooth sign, we used mouse models to investigate the role of ARL13B during cerebellar development. We found ARL13B regulates superior cerebellar peduncle targeting and these fiber tracts require Hedgehog signaling for proper guidance. However, in mouse the Joubert-causing R79Q mutation in ARL13B does not disrupt Hedgehog signaling nor does it impact tract targeting. We found a small cerebellar vermis in mice lacking ARL13B function but no cerebellar vermis hypoplasia in mice expressing the Joubert-causing R79Q mutation. Additionally, mice expressing a cilia-excluded variant of ARL13B that transduces Hedgehog normally, showed normal tract targeting and vermis size. Taken together, our data indicate that ARL13B is critical for superior cerebellar peduncle targeting, likely via Hedgehog signaling, as well as control of cerebellar vermis size. Thus, our work highlights the complexity of ARL13B in molar tooth sign etiology.Summary statementJoubert syndrome is diagnosed by the hindbrain “molar tooth sign” malformation. Using mouse models, we show loss of the ciliary GTPase ARL13B, mutations in which lead to Joubert syndrome, result in two features of the molar tooth sign: hypoplasia of the cerebellar vermis and inappropriate targeting of the superior cerebellar peduncles. Furthermore, we demonstrate that loss of vertebrate Hedgehog signaling may be the underlying disrupted mechanism as we extend its role in axon guidance to the superior cerebellar peduncles.

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ARL13B regulates Sonic hedgehog signaling from outside primary cilia

Cited by 65 publications

References 82 publications

Interaction of INPP5E with ARL13B is essential for its ciliary membrane retention but dispensable for its ciliary entry

Interaction of INPP5E with ARL13B is essential for its ciliary membrane retention but dispensable for its ciliary entry

A eukaryote-wide perspective on the diversity and evolution of the ARF GTPase protein family

Smoothened and ARL13B are critical in mouse for superior cerebellar peduncle targeting

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