Chondrocyte primary cilia shorten in response to osmotic challenge and are sites for endocytosis

Rich, Darren R.; Clark, Arthur W.

doi:10.1016/j.joca.2012.04.017

Cited by 42 publications

(61 citation statements)

References 34 publications

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“…This suggests that different types of stimuli, or differences in the intensity and duration of the loading regime might regulate cilia structure to different extents. Indeed, a similarly low level of cilia disassembly was observed for chondrocytes in situ during short-term osmotic loading where cilia length was reduced by just 10% 42 .…”

Section: Discussionmentioning

confidence: 54%

Primary cilia disassembly down-regulates mechanosensitive hedgehog signalling: a feedback mechanism controlling ADAMTS-5 expression in chondrocytes

Thompson

Chapple

Knight

2014

Osteoarthritis and Cartilage

104

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SummaryObjectiveHedgehog signalling is mediated by the primary cilium and promotes cartilage degeneration in osteoarthritis. Primary cilia are influenced by pathological stimuli and cilia length and prevalence are increased in osteoarthritic cartilage. This study aims to investigate the relationship between mechanical loading, hedgehog signalling and cilia disassembly in articular chondrocytes.MethodsPrimary bovine articular chondrocytes were subjected to cyclic tensile strain (CTS; 0.33 Hz, 10% or 20% strain). Hedgehog pathway activation (Ptch1, Gli1) and A Disintegrin And Metalloproteinase with Thrombospondin Motifs 5 (ADAMTS-5) expression were assessed by real-time PCR. A chondrocyte cell line generated from the Tg737ORPK mouse was used to investigate the role of the cilium in this response. Cilia length and prevalence were quantified by immunocytochemistry and confocal microscopy.ResultsMechanical strain upregulates Indian hedgehog expression and activates hedgehog signalling. Ptch1, Gli1 and ADAMTS-5 expression were increased following 10% CTS, but not 20% CTS. Pathway activation requires a functioning primary cilium and is not observed in Tg737ORPK cells lacking cilia. Mechanical loading significantly reduced cilium length such that cilia became progressively shorter with increasing strain magnitude. Inhibition of histone deacetylase 6 (HDAC6), a tubulin deacetylase, prevented cilia disassembly and restored mechanosensitive hedgehog signalling and ADAMTS-5 expression at 20% CTS.ConclusionsThis study demonstrates for the first time that mechanical loading activates primary cilia-mediated hedgehog signalling and ADAMTS-5 expression in adult articular chondrocytes, but that this response is lost at high strains due to HDAC6-mediated cilia disassembly. The study provides new mechanistic insight into the role of primary cilia and mechanical loading in articular cartilage.

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Section: Discussionmentioning

confidence: 54%

Primary cilia disassembly down-regulates mechanosensitive hedgehog signalling: a feedback mechanism controlling ADAMTS-5 expression in chondrocytes

Thompson

Chapple

Knight

2014

Osteoarthritis and Cartilage

104

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“…The primary cilium has been described as a site that is enriched for endocytotic activity in situ (25). To investigate the possibility that the disruption of IFT88 and the primary cilium might affect LRP-1–mediated endocytosis of aggrecanases, we cocultured cells with FLAG-tagged, ADAMTS-5 (TS5-3) (42), termed FLAG-TS-5, and monitored uptake.…”

Section: Resultsmentioning

confidence: 99%

“…More broadly, links between the cilium and endocytosis have also been described (14, 22, 24–27). In particular, Schou et al (27) describes a caveolin-enriched microdomain at the ciliary transition zone that regulates Hh signal transduction within the ciliary axoneme.…”

Section: Discussionmentioning

confidence: 99%

“…The most famous roles for the cilium, and certainly IFT, include the transduction of signaling downstream to Hedgehog (Hh) ligands (19), mechanical stimuli (20), and growth factors (21–23); however, the ciliome is now associated with the regulation of a plethora of cell biology through both ciliary and potentially nonciliary mechanisms. Microscopy studies of cilia in culture and in situ , including in tissues of the joint, such as synovium and cartilage, describe the association between the cilium, particularly the ciliary pocket, and vesicles of the endocytosis system (24–26). This is functionally important for cilia, downstream to growth factors and Hh (22, 27); however, it remains unknown whether the ciliary pocket is as important to global cellular endocytosis in mammalian cells as the analogous flagellar pocket is for trypanosomes (28).…”

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confidence: 99%

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Cilia protein IFT88 regulates extracellular protease activity by optimizing LRP‐1–mediated endocytosis

et al. 2018

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Matrix protease activity is fundamental to developmental tissue patterning and remains influential in adult homeostasis. In cartilage, the principal matrix proteoglycan is aggrecan, the protease-mediated catabolism of which defines arthritis; however, the pathophysiologic mechanisms that drive aberrant aggrecanolytic activity remain unclear. Human ciliopathies exhibit altered matrix, which has been proposed to be the result of dysregulated hedgehog signaling that is tuned within the primary cilium. Here, we report that disruption of intraflagellar transport protein 88 (IFT88), a core ciliary trafficking protein, increases chondrocyte aggrecanase activity in vitro. We find that the receptor for protease endocytosis in chondrocytes, LDL receptor–related protein 1 (LRP-1), is unevenly distributed over the cell membrane, often concentrated at the site of cilia assembly. Hypomorphic mutation of IFT88 disturbs this apparent hot spot for protease uptake, increases receptor shedding, and results in a reduced rate of protease clearance from the extracellular space. We propose that IFT88 and/or the cilium regulates the extracellular remodeling of matrix—independently of Hedgehog regulation—by enabling rapid LRP-1–mediated endocytosis of proteases, potentially by supporting the creation of a ciliary pocket. This result highlights new roles for the cilium’s machinery in matrix turnover and LRP-1 function, with potential relevance in a range of diseases.—Coveney, C. R., Collins, I., Mc Fie, M., Chanalaris, A., Yamamoto, K., Wann, A. K. T. Cilia protein IFT88 regulates extracellular protease activity by optimizing LRP-1–mediated endocytosis.

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“…These structures might represent membrane invaginations resulting from endocytic events. Endocytosis is known to occur at the base of the primary cilium in mammalian cells and trypanosomatids (Brown et al ., 1965; Duszenko et al ., 1988; Bates et al ., 1989; Field and Carrington, 2009; Molla-Herman et al ., 2010; Rattner et al ., 2010; Rich and Clark, 2012). The ciliary pocket has been the focus of much of this work, although clathrin-mediated endocytosis components have also been observed at the base of cilia and flagella lacking morphologically identifiable pockets (Molla-Herman et al ., 2010; Kaplan et al ., 2012).…”

Section: Discussionmentioning

confidence: 99%

The Rilp-like proteins Rilpl1 and Rilpl2 regulate ciliary membrane content

Schaub

Stearns

2013

MBoC

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Chondrocyte primary cilia shorten in response to osmotic challenge and are sites for endocytosis

Abstract: We demonstrate that live ex vivo chondrocyte primary cilia are capable of shortening within minutes in response to osmotic challenge and provide subcellular and cellular evidence that chondrocyte primary cilia are deeply invaginated in a ciliary pocket which contains sites for endocytosis.

Cited by 42 publications

References 34 publications

Primary cilia disassembly down-regulates mechanosensitive hedgehog signalling: a feedback mechanism controlling ADAMTS-5 expression in chondrocytes

Primary cilia disassembly down-regulates mechanosensitive hedgehog signalling: a feedback mechanism controlling ADAMTS-5 expression in chondrocytes

Cilia protein IFT88 regulates extracellular protease activity by optimizing LRP‐1–mediated endocytosis

The Rilp-like proteins Rilpl1 and Rilpl2 regulate ciliary membrane content

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