1,721,007 research outputs found
The primary cilium influences interleukin-1β-induced NFκB signalling by regulating IKK activity
No full textThe primary cilium is an organelle acting as a master regulator of cellular signalling. We have previously shown that disruption of primary cilia assembly, through targeting intraflagellar transport, is associated with muted nitric oxide and prostaglandin responses to the inflammatory cytokine interleukin-1β (IL-1β). Here, we show that loss of the primary cilium disrupts specific molecular signalling events in cytosolic NFκB signalling. The induction of cyclooxygenase 2 (COX2) and inducible nitrous oxide synthase (iNOS) protein is abolished. Cells unable to assemble cilia exhibit unaffected activation of IκB kinase (IKK), but delayed and reduced degradation of IκB, due to diminished phosphorylation of inhibitor of kappa B (IκB) by IKK. This results in both delayed and reduced NFκB p65 nuclear translocation and nuclear transcript binding. We also demonstrate that heat shock protein 27 (hsp27), an established regulator of IKK, is localized to the ciliary axoneme and cellular levels are dramatically disrupted with loss of the primary cilium. These results suggest that the primary cilia compartment exerts influence over NFκB signalling. We propose that the cilium is a locality for regulation of the molecular events defining NFκB signalling events, tuning signalling as appropriate
Primary cilia elongation in response to interleukin-1 mediates the inflammatory response
Full text linkPrimary cilia are singular, cytoskeletal organelles present in the majority of mammalian cell types where they function as coordinating centres for mechanotransduction, Wnt and hedgehog signalling. The length of the primary cilium is proposed to modulate cilia function, governed in part by the activity of intraflagellar transport (IFT). In articular cartilage, primary cilia length is increased and hedgehog signaling activated in osteoarthritis (OA). Here, we examine primary cilia length with exposure to the quintessential inflammatory cytokine interleukin-1 (IL-1), which is up-regulated in OA. We then test the hypothesis that the cilium is involved in mediating the downstream inflammatory response. Primary chondrocytes treated with IL-1 exhibited a 50 % increase in cilia length after 3 h exposure. IL-1-induced cilia elongation was also observed in human fibroblasts. In chondrocytes, this elongation occurred via a protein kinase A (PKA)-dependent mechanism. G-protein coupled adenylate cyclase also regulated the length of chondrocyte primary cilia but not downstream of IL-1. Chondrocytes treated with IL-1 exhibit a characteristic increase in the release of the inflammatory chemokines, nitric oxide and prostaglandin E2. However, in cells with a mutation in IFT88 whereby the cilia structure is lost, this response to IL-1 was significantly attenuated and, in the case of nitric oxide, completely abolished. Inhibition of IL-1-induced cilia elongation by PKA inhibition also attenuated the chemokine response. These results suggest that cilia assembly regulates the response to inflammatory cytokines. Therefore, the cilia proteome may provide a novel therapeutic target for the treatment of inflammatory pathologies, including OA
Wear potential in the artificial shoulder and its relation to congruency: a finite element investigation
No full textSurface topography regulates wnt signaling through control of primary cilia structure in mesenchymal stem cells
No full textThe primary cilium regulates cellular signalling including influencing wnt sensitivity by sequestering β-catenin within the ciliary compartment. Topographic regulation of intracellular actin-myosin tension can control stem cell fate of which wnt is an important mediator. We hypothesized that topography influences mesenchymal stem cell (MSC) wnt signaling through the regulation of primary cilia structure and function. MSCs cultured on grooves expressed elongated primary cilia, through reduced actin organization. siRNA inhibition of anterograde intraflagellar transport (IFT88) reduced cilia length and increased active nuclear β-catenin. Conversely, increased primary cilia assembly in MSCs cultured on the grooves was associated with decreased levels of nuclear active β-catenin, axin-2 induction and proliferation, in response to wnt3a. This negative regulation, on grooved topography, was reversed by siRNA to IFT88. This indicates that subtle regulation of IFT and associated cilia structure, tunes the wnt response controlling stem cell differentiation
Competitive interactions between hedgehog and cytokine signalling: crosstalk at the chondrocyte primary cilium?
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The primary cilium orchestrates chondrocyte mechanotransduction
No full textPurpose: to understand the role of the chondrocyte primary cilium in mechanotransduction. The primary cilium is a singular organelle protruding outward from the mature centriole into the extracellular space, decorated with many receptors and integrins. The tubulin scaffold, ciliary membrane and proteome are constructed and maintained by dynein motors and intraflagellar transport cargos. In many cell types such as kidney epithelia, vascular endothelium and osteocytes, primary cilia are involved in mechanotransduction, often through the activities of polycystin 1 and 2 located on the cilium. Physiologically cartilage experiences mechanical signals, altering cell behaviour, that include compression and fluid flow. It is thought aberrant mechanotransduction may be one factor in the development of tissue pathology. Here we test the hypothesis that the cilium is essential for chondrocyte mechanotransduction and the up-regulation of proteoglycan synthesis through an established purinergic pathway involving the release of ATP and subsequent activation of Ca2+ signalling.Methods: to test this we used a hypomorphic mutation of Tg737, which encodes for IFT88, and abolishes genesis and growth of the cilium and which has been shown in vivo to result in murine matrix patterning defects. A well-established 3D agarose culture system was implemented to allow compressive loading of murine WT and Tg737 chondrocytes in culture followed by the quantification of ATP release with a luciferase assay, calcium transients by means of Fluo-4 imaging, and matrix production by qPCR and biochemical assay. Additionally expression of purinergic receptors (P2R) and polycystins (PC) 1 and 2 were assessed by western blot and immunocytochemistry.Results: compression of WT chondrocytes increased calcium transients (p<0.05) and matrix production at gene and protein levels (p<0.05) however these mechanosensitive responses were not present in Tg737 chondrocytes. Mechanosensitive ATP release (p<0.01) was maintained between WT and Tg737 cells implying that the cilium is required for ATP reception or transduction. Indeed, exogenous addition of ATP up-regulated Ca2+ transients in WT (p<0.001) but did not in Tg737 cells, although there were no differences in P2R expression. In Tg737 cells PC-1 expression was altered such that the full size protein product was absent.Conclusions: we conclude that the primary cilium is essential for chondrocyte mechanotransduction through the regulation of purinergic Ca2+ signalling. We speculate that this may be attributed to a role for the cilia protein polycystin-1. This demonstrates the central role for the chondrocyte primary cilium in cartilage physiology in the context of the chondrocyte response to mechanical stimuli
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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