Regulation of the ARL6 GTPase cycle within the primary cilium
Abstract/Contents
- Abstract
- Primary cilia organize cellular signaling cascades by dynamically concentrating signaling receptors in response to extracellular cues. In particular, the removal of signaling molecules from cilia tunes the sensitivity of major signaling pathways but remains a poorly understood process. A major sorting complex for the cilium is the BBSome, a coat-like complex of eight Bardet-Biedl Syndrome (BBS) proteins, which directly recognizes signal receptors and co-moves with the intraflagellar transport (IFT) machinery within cilia. Importantly, recruitment of the BBSome to membranes relies on GTP loading onto the ARF-like GTPase ARL6/BBS3, but no regulators for the nucleotide state of ARL6 have been identified so far. Identification of the guanine nucleotide exchange factor (GEF) and GTPase-activating protein (GAP) for ARL6 is key to pinpointing the locations where BBSome coats assemble and disassemble, respectively, and will further shed light on the pathomechanisms of BBS. Because mutations in the Rab-like GTPase and IFT-B subunit IFT27/RABL4 were recently identified in a BBS family, we sought to characterize the function of IFT27 in BBSome-mediated trafficking. Strikingly, ARL6, BBSome and the candidate BBSome cargo GPR161 accumulated in IFT27-deficient cilia, and photokinetic assays on stable cell lines expressing fluorescently tagged BBSome revealed that IFT27 perturbation reduces BBSome exit rates ~3-fold while leaving BBSome entry rates unaffected. At the molecular level, IFT27 disengages from the rest of IFT-B to directly associate with and stabilize the nucleotide-free form of ARL6 against aggregation. Thus, we propose that within cilia, IFT27 dissociates from IFT-B to directly participate in GTP loading onto ARL6, promoting the assembly of exit-bound and cargo-laden BBSome coats. Additional mechanisms for the regulation of IFT27 and ARL6 within cilia are discussed.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Liew, Gerald Ming Jie |
|---|---|
| Associated with | Stanford University, Department of Biochemistry. |
| Primary advisor | Nachury, Maxence |
| Thesis advisor | Nachury, Maxence |
| Thesis advisor | Beachy, Philip Arden |
| Thesis advisor | Stearns, Tim |
| Thesis advisor | Straight, Aaron, 1966- |
| Advisor | Beachy, Philip Arden |
| Advisor | Stearns, Tim |
| Advisor | Straight, Aaron, 1966- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Gerald Ming Jie Liew. |
|---|---|
| Note | Submitted to the Department of Biochemistry. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Gerald Ming Jie Liew
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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