8,822 research outputs found
Active Tension: The Role of Cadherin Adhesion and Signaling in Generating Junctional Contractility
No full textIn this chapter, we discuss the cell biology of contractility at cell–cell junctions. As discussed elsewhere in this volume, contractile forces play key roles in development and tissue homeostasis. Here, we review our understanding of the cellular mechanisms that functionally and physically link cadherin adhesion to the actomyosin contractile apparatus of the cell. Focusing on epithelia, we argue that E-cadherin junctions can be considered as active mechanical agents, which contribute to the assembly of actomyosin at the junctional cortex itself. This reflects cortical signaling, notably that regulated by the Rho GTPase, coordinated with actin regulation at junctions. The product, contractile tension at junctions, can then be regarded as an emergent property of a complex dynamical system that integrates adhesion with the cytoskeleton
Supplementary Figure 1, (a) of the paper Feedback regulation through myosin II confers robustness on RhoA signalling at E-cadherin junctions.
No full textRhoA, E-cadherin and ZO-1 localization in TCA-fixed MCF-7 cells. Images were acquired using a confocal microscope and different Z-sections were used to do an XZ view (shown in the figure of the paper
Willin, an upstream component of the Hippo signaling pathway, orchestrates mammalian peripheral nerve fibroblasts
No full textWillin/FRMD6 was first identified in the rat sciatic nerve, which is composed of neurons, Schwann cells, and fibroblasts. Willin is an upstream component of the Hippo signaling pathway, which results in the inactivation of the transcriptional coactivator YAP through Ser127 phosphorylation. This in turn suppresses the expression of genes involved in cell growth, proliferation and cancer development ensuring the control of organ size, cell contact inhibition and apoptosis. Here we show that in the mammalian sciatic nerve, Willin is predominantly expressed in fibroblasts and that Willin expression activates the Hippo signaling cascade and induces YAP translocation from the nucleus to the cytoplasm. In addition within these cells, although it inhibits cellular proliferation, Willin expression induces a quicker directional migration towards scratch closure and an increased expression of factors linked to nerve regeneration. These results show that Willin modulates sciatic nerve fibroblast activity indicating that Willin may have a potential role in the regeneration of the peripheral nervous system.Peer reviewe
Data collection for 'Feedback regulation through myosin II confers robustness on RhoA signalling at E-cadherin junctions."
No full textThe data collection contains 49 original images collected during experiments, 3 videos, supplementary material including experimental foundations of the model and extension of the stimulation/expression model to 3 dimensions
Alpha-catenins control cardiomyocyte proliferation by regulating Yap activity
No full textRationale: Shortly after birth, muscle cells of the mammalian heart lose their ability to divide. Thus, they are unable to effectively replace dying cells in the injured heart. The recent discovery that the transcriptional coactivator Yes-associated protein (Yap) is necessary and sufficient for cardiomyocyte proliferation has gained considerable attention. However, the upstream regulators and signaling pathways that control Yap activity in the heart are poorly understood.
Objective: To investigate the role of alpha-catenins in the heart using cardiac-specific alpha E- and alpha T-catenin double knockout mice.
Methods and Results: We used 2 cardiac-specific Cre transgenes to delete both alpha E-catenin (Ctnna1) and alpha T-catenin (Ctnna3) genes either in the perinatal or in the adult heart. Perinatal depletion of alpha-catenins increased cardiomyocyte number in the postnatal heart. Increased nuclear Yap and the cell cycle regulator cyclin D1 accompanied cardiomyocyte proliferation in the alpha-catenin double knockout hearts. Fetal genes were increased in the alpha-catenin double knockout hearts indicating a less mature cardiac gene expression profile. Knockdown of alpha-catenins in neonatal rat cardiomyocytes also resulted in increased proliferation, which could be blocked by knockdown of Yap. Finally, inactivation of alpha-catenins in the adult heart using an inducible Cre led to increased nuclear Yap and cardiomyocyte proliferation and improved contractility after myocardial infarction.
Conclusions: These studies demonstrate that alpha-catenins are critical regulators of Yap, a transcriptional coactivator essential for cardiomyocyte proliferation. Furthermore, we provide proof of concept that inhibiting alpha-catenins might be a useful strategy to promote myocardial regeneration after injury
Network interactions allowing myosin II to feedback to RhoA: sequencing, predictive modelling, and experimentation
No full text8 x supplementary figures; 2 x supplementary table; 3 x videos, supplementary noteSupplementary Figure 1 Myosin II supports a stable Rho zone at the ZASupplementary Figure 2 p190B RhoGAP degrades the junctional Rho zone when NMII is inactivatedSupplementary Figure 3 Rnd3 recruits p190B to the ZA when NMII is inhibitedSupplementary Figure 4 ROCK-1 phosphorylates Rnd3 to support junctional Rho signalingSupplementary Figure 5 Myosin II scaffolds ROCK-1 at the epithelial Zonula AdherensSupplementary Figure 6 Bistable properties of RhoA localization at cell-cell junctionsSupplementary Figure 7 Bright field/DIC images corresponding to Figures 1a, 1f, 2h, 3a, 3b, 5h and supplementary figures 1c, 1e, 4eSupplementary Figure 8 Uncropped western blotsSupplementary Table 1 Sequences of siRNA and primers used for the studySupplementary Table 2 Statistical Source dataSupplementary Video 1GFP-AHPH localizes at the zonula adherens of epithelial cells.Z-stacks of GFP-AHPH and RFP-UtrCH acquired by spinning disc confocal microscopy.Supplementary Video 2GFP-AHPH exhibits stability on the time scale of minutes. Time-lapse imaging of GFP-APHPH (transfected in MCF-7 cells) acquired over a span of 30 minutes.Supplementary Video 3ROCK-1 inhibition causes accumulation of p190B Rho GAP at the cell-cell junctions.MCF-7 cells were transfected with GFP-p190B RhoGAP and time-lapsed imaging was performed briefly before and after addition of Y-27632 (30 μM)(20-minutes post-treatment).Supplementary Notes include:Experimental foundations of the model.Computational model.Supplementary Note Table 1. Hill (K), maximal association rates (b) and decay (a) constants in the stimulation repression model shown in Scheme 1. Implications of the one dimensional modelEffect of removing feedback from ROCK1 to RhoA.Supplementary Note Table 2. Kinetic equations for the reduced subsystem shown in Scheme 2.Effect of removing feedback from NMIIA to ROCK1.Effect of adding negative feedback from Rnd3 to ROCK1.Extension of the stimulation/repression model to 3 dimensionsDerivation of the explicit form for the equations used in the spatial model.Supplementary Note Table 3. Kinetic equations for the stimulation repression model in 3 dimensionsSupplementary Note Table 4. Steady state cortical concentrations of the different species in the 3dimensional modelSupplementary Note Table 5. Variable transformation between the one dimensional stimulation repression model and its extension in 3 dimensions.Numerical simulations for the 3 dimensional model.Supplementary Note Table 6. Dissociation rates, binding affinities and activation constants used for modeling in three dimensions Supplementary Note Table 7. Initial concentrations and diffusion coefficients of species in the 3 - dimensional modelling.Implications of the model for cortical signaling at the ZA.Supplementary Note Table 6. Dissociation rates, binding affinities and activation constants used for modeling in three dimensions Supplementary Note Table 7. Initial concentrations and diffusion coefficients of species in the 3 - dimensional modelling.Implications of the model for cortical signaling at the ZA
Par3 integrates Tiam1 and phosphatidylinositol 3-kinase signaling to change apical membrane identity
No full textPathogens can alter epithelial polarity by recruiting polarity proteins to the apical
membrane, but how a change in protein localization is linked to polarity disruption is not
clear. In this study, we used chemically induced dimerization to rapidly relocalize proteins
from the cytosol to the apical surface. We demonstrate that forced apical localization of Par3,
which is normally restricted to tight junctions, is sufficient to alter apical membrane identity
through its interactions with phosphatidylinositol 3-kinase (PI3K) and the Rac1 guanine nucleotide
exchange factor Tiam1. We further show that PI3K activity is required upstream of
Rac1, and that simultaneously targeting PI3K and Tiam1 to the apical membrane has a synergistic
effect on membrane remodeling. Thus, Par3 coordinates the action of PI3K and Tiam1
to define membrane identity, revealing a signaling mechanism that can be exploited by human
mucosal pathogens
An alpha-catenin deja vu
No full textalpha-catenin exists as part of the cadherin-catenin adhesion complex as well as in a cytoplasmic pool. However, which of these pools is responsible for its biological impact remains controversial. A structure-function analysis in Drosophila melanogaster illuminates how the molecular properties of alpha-catenin translate into functional outcomes in an intact organism
Retreatment with interferon-alpha and ribavirin in primary interferon-alpha non-responders with chronic hepatitis C
No full textBackground/Aims: Combination therapy with interferon-alpha (IFN-alpha) plus ribavirin is more efficacious than IFN-alpha monotherapy in previously untreated patients with chronic hepatitis C and patients with IFN-alpha relapse. Only limited data are available in IFN-alpha non-responders. In a multicenter trial we therefore evaluated the efficacy of combination therapy in IFN-alpha-resistant chronic hepatitis C. Methods: Eighty-two patients (mean age 46.8 years, 54 males, 28 females) with chronic hepatitis C were treated with IFN-alpha-2a (3 x 6 MIU/week) and ribavirin (14 mg/kg daily) for 12 weeks. Thereafter, treatment was continued only in virological responders (undetectable serum HCV RNA at week 12) with an IFN-alpha dose of 3 x 3 MIU/week and without ribavirin for a further 9 months. The primary study endpoint was an undetectable HCV RNA by RT-PCR at the end of the 24-week follow-up period. Results: After 12 weeks of combination therapy, an initial virological response was observed in 29 of 82 (35.4%) patients. Due to a high breakthrough rate after IFN-a dose reduction and ribavirin discontinuation, an end-of-treatment response was only achieved in 12 of 82 (14.6%) patients. After the follow-up period, a sustained virological response was observed in 8 of 82 (9.8%) patients. Infection with HCV genotype 3 was the only pretreatment parameter, which could predict a sustained response (HCV-1, 5%; HCV-3, 57.1%; p < 0.001). Conclusions: Despite a high initial response rate of 35.4%, sustained viral clearance was achieved only in 9.8% of the retreated primary IFN-alpha non-responders. Higher IFN-alpha induction and maintenance dose, as well as prolonged ribavirin treatment may possibly increase the virological response rates in non-responders, particularly in those infected by HCV-1
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