scholarly journals Balancing the length of distal tip is key for stability and signalling function of primary cilia

2021 ◽  
Author(s):  
Taishi Kanamaru ◽  
Annett Neuner ◽  
Bahtiyar Kurtulmus ◽  
Gislene Pereira
Keyword(s):  
Sonic Hedgehog ◽  
Live Cell Imaging ◽  
Primary Cilia ◽  
Cell Imaging ◽  
Growth Inhibitor ◽  
Distal Segment ◽  
Segment Length ◽  
Functional Transition ◽  
Sensory Cilia ◽  
Signalling Transduction

Primary cilia are antenna-like organelles required for signalling transduction. How cilia structure is mechanistically maintained at steady-state to promote signalling is largely unknown. Here, we define that mammalian primary cilia are formed by middle and distal segments, in analogy to sensory cilia of lower eukaryotes. The analysis of middle/distal segmentation indicated that perturbations leading to cilia over-elongation influenced middle or distal segment length with a different impact on cilia behaviour. We identified Septins as novel repressors of distal segment growth. We show that Septins control the localisation of MKS3 and CEP290 required for a functional transition zone, and through this the entrance of the microtubule-capping kinesin KIF7, a cilia-growth inhibitor, into the cilium. Live-cell imaging and analysis of sonic-hedgehog (SHH) signalling activation established that distal segment over-extension increased cilia excision events and decreased SHH activation. Our data underlies the importance of understanding cilia segmentation for length control and cilia-dependent signalling.

scholarly journals Angiomotin isoform 2 promotes binding of PALS1 to KIF13B at the base of primary cilia and suppresses ciliary elongation

2021 ◽  
Author(s):  
Stine K Morthorst ◽  
Camilla Nielsen ◽  
Pietro Farinelli ◽  
Zeinab Anvarian ◽  
Christina B. R. Rasmussen ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Live Cell Imaging ◽  
Primary Cilia ◽  
Cell Imaging ◽  
Vesicle Transport ◽  
Imaging Analysis ◽  
Ciliary Function ◽  
Cargo Transport ◽  
Direct Binding ◽  
Crumbs Complex

The kinesin-3 motor KIF13B functions in endocytosis, vesicle transport, and regulation of ciliary length and signaling. Direct binding of the membrane-associated guanylate kinase (MAGUK) DLG1 to KIF13Bs MAGUK-binding stalk (MBS) domain relieves motor autoinhibition and promotes microtubule plus end-directed cargo transport. Here we characterize Angiomotin isoform 2 (Ap80) as a novel KIF13B interactor that promotes binding of another MAGUK, the polarity protein and Crumbs complex component PALS1, to KIF13B. Live cell imaging analysis indicated that Ap80 is concentrated at the base of primary cilia and recruits PALS1 to this site, but is not itself a cargo of KIF13B. Consistent with a ciliary function for Ap80, its depletion led to elongated primary cilia and altered IGF-1 signaling in cultured mammalian cells. Our results suggest that Ap80 may specifically activate KIF13B cargo binding at the base of primary cilia to regulate ciliary length and signaling.

scholarly journals Transient accumulation and bidirectional movement of KIF13B in primary cilia

2021 ◽  
Author(s):  
Alice Dupont Juhl ◽  
Zeinab Anvarian ◽  
Julia Berges ◽  
Daniel Wustner ◽  
Lotte B Pedersen
Keyword(s):  
Mammalian Cells ◽  
Live Cell Imaging ◽  
Primary Cilia ◽  
Cell Imaging ◽  
Intraflagellar Transport ◽  
Cytoplasmic Dynein ◽  
Ciliary Membrane ◽  
Bidirectional Movement ◽  
And Function ◽  
Male Specific

Primary cilia are microtubule-based sensory organelles whose assembly and function rely on the conserved bidirectional intraflagellar transport (IFT) system, which is powered by anterograde kinesin-2 and retrograde cytoplasmic dynein 2 motors. Nematodes additionally employ a male-specific kinesin-3 motor, KLP-6, which regulates ciliary content and function by promoting release of bioactive extracellular vesicles (EVs) from cilia. Here we show by live cell imaging that a KLP-6 homolog, KIF13B, undergoes bursts of bidirectional movement within primary cilia of cultured mammalian cells at 0.64 +/- 0.07 μm/s in the anterograde direction and at 0.39 +/- 0.06 μm/s in the retrograde direction, reminiscent of conventional IFT. In addition, we found that KIF13B undergoes EV-like release from the ciliary tip whereas a ciliary membrane marker, SMO-tRFP, remains stably associated with cilia during such EV release. Our results suggest that KIF13B, similar to KLP-6, regulates ciliary membrane content by promoting ciliary EV release, possibly in coordination with conventional IFT.

scholarly journals Katanin p60-like 1 sculpts the cytoskeleton in mechanosensory cilia

2020 ◽  
Vol 220 (1) ◽  
Author(s):  
Landi Sun ◽  
Lihong Cui ◽  
Zhen Liu ◽  
Qixuan Wang ◽  
Zhaoyu Xue ◽  
...  
Keyword(s):  
Live Cell Imaging ◽  
Cell Imaging ◽  
Electron Tomography ◽  
3D Structure ◽  
Functional Roles ◽  
Microtubule Severing ◽  
Structure And Dynamics ◽  
Sensory Cilia ◽  
Potential Factors ◽  
Neuronal Type

Mechanoreceptor cells develop a specialized cytoskeleton that plays structural and sensory roles at the site of mechanotransduction. However, little is known about how the cytoskeleton is organized and formed. Using electron tomography and live-cell imaging, we resolve the 3D structure and dynamics of the microtubule-based cytoskeleton in fly campaniform mechanosensory cilia. Investigating the formation of the cytoskeleton, we find that katanin p60-like 1 (kat-60L1), a neuronal type of microtubule-severing enzyme, serves two functions. First, it amplifies the mass of microtubules to form the dense microtubule arrays inside the sensory cilia. Second, it generates short microtubules that are required to build the nanoscopic cytoskeleton at the mechanotransduction site. Additional analyses further reveal the functional roles of Patronin and other potential factors in the local regulatory network. In all, our results characterize the specialized cytoskeleton in fly external mechanosensory cilia at near-molecular resolution and provide mechanistic insights into how it is formed.

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