Primary cilia organize signaling pathways such as vision, olfaction and Hedgehog signaling. The movements of signaling receptors into, inside and out of cilium are critical for the correct regulation of these pathways, yet our understanding of the basic mechanisms governing signaling receptor trafficking through cilia remains fragmentary. Past work from the lab identified and characterized the BBSome, a protein complex that ferries signaling receptors out of cilia. The relevance of the BBSome to human health and disease is evidence by the fact that BBSome dysfunction causes Bardet-Biedl Syndrome (BBS), a hereditary disease characterized by obesity, retinal degeneration, polydactyly and kidney malformations. The major goal of this proposal is to determine how the BBSome selects signaling receptors for removal from cilia. The emphasis in this funding period will be on investigating the role of ubiquitin in tagging membrane proteins for removal from cilia. Preliminary data indicate the existence of a ciliary machinery that recognizes activated GPCRs, ubiquitinates them and sorts ubiquitinated GPCRs out of cilia. We will characterize the molecules acting at each of these steps using quantitative assays for signal-dependent GPCR exit. The hierarchical ordering of the molecular cogs and levers that affix and read ubiquitin on proteins that need to exit cilia promises to uncover a multi-step pathway reminiscent of the ESCRT machinery responsible for degradative sorting. Finally, the fate of GPCRs that exit cilia will be tracked by single-molecule imaging to determine whether endocytosis is coupled to ciliary exit or whether GPCRs instead diffuse into the plasma membrane after exiting cilia. The proposed studies will cast new light on how the ciliary abundance of proteins is regulated and open the door to a mechanistic investigation of ciliary quality control.

Public Health Relevance

Dysfunction of the primary cilium underlie the etiology of Bardet-Biedl Syndrome, a disorder characterized by obesity, skeletal abnormalities, kidney cysts and retinal degeneration. The proposal aims to uncover the basic mechanisms by which Bardet-Biedl Syndrome proteins maintain the protein content of primary cilia. If successful, this research program will further our understanding of retinal degeneration and obesity and provide novel means for therapeutic intervention.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM089933-12
Application #
10086988
Study Section
Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
Program Officer
Ainsztein, Alexandra M
Project Start
2010-04-01
Project End
2024-01-31
Budget Start
2021-02-01
Budget End
2022-01-31
Support Year
12
Fiscal Year
2021
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
094878337
City
San Francisco
State
CA
Country
United States
Zip Code
94143
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Ye, Fan; Nager, Andrew R; Nachury, Maxence V (2018) BBSome trains remove activated GPCRs from cilia by enabling passage through the transition zone. J Cell Biol 217:1847-1868
Breslow, David K; Hoogendoorn, Sascha; Kopp, Adam R et al. (2018) A CRISPR-based screen for Hedgehog signaling provides insights into ciliary function and ciliopathies. Nat Genet 50:460-471
Steinman, Jonathan B; Santarossa, Cristina C; Miller, Rand M et al. (2017) Chemical structure-guided design of dynapyrazoles, cell-permeable dynein inhibitors with a unique mode of action. Elife 6:
Nager, Andrew R; Goldstein, Jaclyn S; Herranz-PĂ©rez, Vicente et al. (2017) An Actin Network Dispatches Ciliary GPCRs into Extracellular Vesicles to Modulate Signaling. Cell 168:252-263.e14
Lee, Tina H; Nachury, Maxence V (2017) Membrane traffic control by cytoskeletal and molecular machines. Mol Biol Cell 28:697-698
Niwa, Shinsuke; Tao, Li; Lu, Sharon Y et al. (2017) BORC Regulates the Axonal Transport of Synaptic Vesicle Precursors by Activating ARL-8. Curr Biol 27:2569-2578.e4
Xu, Zhenjie; Schaedel, Laura; Portran, Didier et al. (2017) Microtubules acquire resistance from mechanical breakage through intralumenal acetylation. Science 356:328-332
Bruel, Ange-Line; Franco, Brunella; Duffourd, Yannis et al. (2017) Fifteen years of research on oral-facial-digital syndromes: from 1 to 16 causal genes. J Med Genet 54:371-380
Portran, Didier; Schaedel, Laura; Xu, Zhenjie et al. (2017) Tubulin acetylation protects long-lived microtubules against mechanical ageing. Nat Cell Biol 19:391-398

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