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Intraflagellar transport trains and motors: Insights from structure.

ABSTRACT: Intraflagellar transport (IFT) sculpts the proteome of cilia and flagella; the antenna-like organelles found on the surface of virtually all human cell types. By delivering proteins to the growing ciliary tip, recycling turnover products, and selectively transporting signalling molecules, IFT has critical roles in cilia biogenesis, quality control, and signal transduction. IFT involves long polymeric arrays, termed IFT trains, which move to and from the ciliary tip under the power of the microtubule-based motor proteins kinesin-II and dynein-2. Recent top-down and bottom-up structural biology approaches are converging on the molecular architecture of the IFT train machinery. Here we review these studies, with a focus on how kinesin-II and dynein-2 assemble, attach to IFT trains, and undergo precise regulation to mediate bidirectional transport.

SUBMITTER: Webb S

PROVIDER: S-EPMC7561706 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Intraflagellar transport trains and motors: Insights from structure.

Webb Stephanie S Mukhopadhyay Aakash G AG Roberts Anthony J AJ

Seminars in cell & developmental biology 20200716

Intraflagellar transport (IFT) sculpts the proteome of cilia and flagella; the antenna-like organelles found on the surface of virtually all human cell types. By delivering proteins to the growing ciliary tip, recycling turnover products, and selectively transporting signalling molecules, IFT has critical roles in cilia biogenesis, quality control, and signal transduction. IFT involves long polymeric arrays, termed IFT trains, which move to and from the ciliary tip under the power of the microtu ...[more]

PMID: 32684327

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Structure of the dynein-2 complex and its assembly with intraflagellar transport trains.

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Conversion of anterograde into retrograde trains is an intrinsic property of intraflagellar transport.

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Extensive structural rearrangement of intraflagellar transport trains underpins bidirectional cargo transport

Project description:Bidirectional transport in cilia is carried out by polymers of the IFTA and IFTB protein complexes, referred to as anterograde and retrograde IFT “trains”. Anterograde trains deliver cargoes from the cell to the ciliary tip, then remodel into retrograde trains for cargo export. We set out to understand how the structure of these trains changes at the tip, and thus how the same IFT complexes can perform opposing transport roles. We use cryo-electron tomography, subtomogram averaging and in-situ cross-linking mass spectrometry to determine the structure of retrograde IFT trains, and compare with the known anterograde train structure. We show that the retrograde train is a two-fold symmetric polymer organised around a central thread of IFTA complexes. We conclude that the structural differences between anterograde and retrograde trains can only be achieved through de novo polymerisation of the retrograde train from individual IFTA/B complexes. Finally we describe how conformational changes to cargo binding sites allow for unidirectional cargo transport in a bidirectional system.

2024-08-21 | PXD049195 | JPOST Repository

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Project description: Not available

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Extensive structural rearrangement of intraflagellar transport trains underpins bidirectional cargo transport (Proteomics

2024-08-21 | PXD049260 | JPOST Repository

Structure and tethering mechanism of dynein-2 intermediate chains in intraflagellar transport.

Project description:Dynein-2 is a large multiprotein complex that powers retrograde intraflagellar transport (IFT) of cargoes within cilia/flagella, but the molecular mechanism underlying this function is still emerging. Distinctively, dynein-2 contains two identical force-generating heavy chains that interact with two different intermediate chains (WDR34 and WDR60). Here, we dissect regulation of dynein-2 function by WDR34 and WDR60 using an integrative approach including cryo-electron microscopy and CRISPR/Cas9-enabled cell biology. A 3.9 Å resolution structure shows how WDR34 and WDR60 use surprisingly different interactions to engage equivalent sites of the two heavy chains. We show that cilia can assemble in the absence of either WDR34 or WDR60 individually, but not both subunits. Dynein-2-dependent distribution of cargoes depends more strongly on WDR60, because the unique N-terminal extension of WDR60 facilitates dynein-2 targeting to cilia. Strikingly, this N-terminal extension can be transplanted onto WDR34 and retain function, suggesting it acts as a flexible tether to the IFT "trains" that assemble at the ciliary base. We discuss how use of unstructured tethers represents an emerging theme in IFT train interactions.

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Optimal sidestepping of intraflagellar transport kinesins regulates structure and function of sensory cilia.

Project description:Cytoskeletal-based molecular motors produce force perpendicular to their direction of movement. However, it remains unknown whether and why motor proteins generate sidesteps movement along their filamentous tracks in vivo. Using Hessian structured illumination microscopy, we located green fluorescent protein (GFP)-labeled intraflagellar transport (IFT) particles inside sensory cilia of live Caenorhabditis elegans with 3-6-nanometer accuracy and 3.4-ms resolution. We found that IFT particles took sidesteps along axoneme microtubules, demonstrating that IFT motors generate torque in a living animal. Kinesin-II and OSM-3-kinesin collaboratively drive anterograde IFT. We showed that the deletion of kinesin-II, a torque-generating motor protein, reduced sidesteps, whereas the increase of neck flexibility of OSM-3-kinesin upregulated sidesteps. Either increase or decrease of sidesteps of IFT kinesins allowed ciliogenesis to the regular length, but changed IFT speeds, disrupted axonemal ninefold symmetry, and inhibited sensory cilia-dependent animal behaviors. Thus, an optimum level of IFT kinesin sidestepping is associated with the structural and functional fidelity of cilia.

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