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Bardet-Biedl Syndrome-associated Small GTPase ARL6 (BBS3) Functions at or near the Ciliary Gate and Modulates Wnt Signaling
The expansive family of metazoan ADP-ribosylation factor and ADP-ribosylation factor-like small GTPases is known to play essential roles in modulating membrane trafficking and cytoskeletal functions. Here, we present the crystal structure of ARL6, mutations in which cause Bardet-Biedl syndrome (BBS3...
Autores principales: | , , , , , , , , , , |
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Formato: | Texto |
Lenguaje: | English |
Publicado: |
American Society for Biochemistry and Molecular Biology
2010
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871489/ https://www.ncbi.nlm.nih.gov/pubmed/20207729 http://dx.doi.org/10.1074/jbc.M109.070953 |
Sumario: | The expansive family of metazoan ADP-ribosylation factor and ADP-ribosylation factor-like small GTPases is known to play essential roles in modulating membrane trafficking and cytoskeletal functions. Here, we present the crystal structure of ARL6, mutations in which cause Bardet-Biedl syndrome (BBS3), and reveal its unique ring-like localization at the distal end of basal bodies, in proximity to the so-called ciliary gate where vesicles carrying ciliary cargo fuse with the membrane. Overproduction of GDP- or GTP-locked variants of ARL6/BBS3 in vivo influences primary cilium length and abundance. ARL6/BBS3 also modulates Wnt signaling, a signal transduction pathway whose association with cilia in vertebrates is just emerging. Importantly, this signaling function is lost in ARL6 variants containing BBS-associated point mutations. By determining the structure of GTP-bound ARL6/BBS3, coupled with functional assays, we provide a mechanistic explanation for such pathogenic alterations, namely altered nucleotide binding. Our findings therefore establish a previously unknown role for ARL6/BBS3 in mammalian ciliary (dis)assembly and Wnt signaling and provide the first structural information for a BBS protein. |
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