Caspase | EPFL Graph Search

Les caspases sont une classe de protéases à cystéine qui reconnaissent chacune une séquence particulière sur certaines protéines et hydrolysent la liaison peptidique côté carboxyle d'un résidu d'aspartate de cette séquence. Ces enzymes jouent un rôle essentiel dans les phénomènes inflammatoires ainsi que dans l'apoptose (mort cellulaire programmée) et la nécrose. Le terme « caspase » est la contraction en anglais de l'expression cysteine-aspartic protease, parfois également écrite cysteine-dependent aspartate-directed protease, voire cysteinyl-aspartate-cleaving protease. Les caspases sont indispensables à l'apoptose des cellules, et jouent un rôle crucial au cours du développement et d'autres stades de la vie adulte. Elles sont dites « exécutrices » (executioner en anglais) en raison leur fonction dans la cellule. Certaines caspases sont également requises par le système immunitaire pour la maturation des lymphocytes. Une apoptose insuffisante est l'un des principaux facteurs contri

Analysis of the Cytoprotective Role of alpha-Crystallins in Cell Survival and Implication of the alpha A-Crystallin C-Terminal Extension Domain in Preventing Bax-Induced Apoptosis

Séverine Hamann

alpha-Crystallins, initially described as the major structural proteins of the lens, belong to the small heat shock protein family. Apart from their function as chaperones, alpha-crystallins are involved in the regulation of intracellular apoptotic signals. alpha A- and alpha B-crystallins have been shown to interfere with the mitochondrial apoptotic pathway triggering Bax pro-apoptotic activity and downstream activation of effector caspases. Differential regulation of alpha-crystallins has been observed in several eye diseases such as age-related macular degeneration and stress-induced and inherited retinal degenerations. Although the function of alpha-crystallins in healthy and diseased retina remains poorly understood, their altered expression in pathological conditions argue in favor of a role in cellular defensive response. In the Rpe65(-/-) mouse model of Leber's congenital amaurosis, we previously observed decreased expression of alpha A- and alpha B-crystallins during disease progression, which was correlated with Bax pro-death activity and photoreceptor apoptosis. In the present study, we demonstrated that alpha-crystallins interacted with pro-apoptotic Bax and displayed cytoprotective action against Bax-triggered apoptosis, as assessed by TUNEL and caspase assays. We further observed in staurosporine-treated photoreceptor-like 661W cells stably overexpressing alpha A- or alpha B-crystallin that Bax-dependent apoptosis and caspase activation were inhibited. Finally, we reported that the C-terminal extension domain of alpha A- crystallin was sufficient to provide protection against Bax-triggered apoptosis. Altogether, these data suggest that alpha-crystallins interfere with Bax-induced apoptosis in several cell types, including the cone-derived 661W cells. They further suggest that alpha A-crystallin-derived peptides might be sufficient to promote cytoprotective action in response to apoptotic cell death.

Public Library of Science2013

Investigation of cell death mechanisms in human lymphatic endothelial cells undergoing photodynamic therapy

Witold Waldemar Kilarski

Background: Photodynamic therapy (PDT) has been shown to induce ablation and functional occlusion of tumor-associated lymphatic vessels. However, direct effects of PDT on lymphatic endothelial cells (LECs) have not been studied so far. The aim of this study was to elucidate molecular mechanisms of cell death induced by PDT in human LECs. Methods: Verteporfin was used as a photosensitizer to investigate PDT-mediated damage of lymphatic vessels in mice using immunofluorescent staining and stereomicroscopy. In vitro dose-response studies were carried-out with crystal violet staining. Immunofluorescence, flow cytometry, immunoblotting and DNA electrophoresis were used to investigate the mechanisms of cell death in human LECs undergoing PDT. Results: PDT induced an increase in the number of propidium iodide positive lymphatic endothelial cells in the mouse dermis. In in vitro studies dose-dependent cytotoxic effects of PDT towards LECs were observed. Typical hallmarks of apoptotic cell death, including Annexin V binding, loss of mitochondrial membrane potential, caspase activation, cleavage of PARP as well as DNA fragmentation were observed in LECs when PDT was used at high irradiation conditions, causing >80% cell death. At lower light fluencies causing

Elsevier Science Bv2016

A Biocompatible in Vivo Ligation Reaction and Its Application for Noninvasive Bioluminescent Imaging of Protease Activity in Living Mice

Ke Cheng, Aurélien Godinat, Douglas Hanahan, Gennady Nikitin

The discovery of biocompatible reactions had a tremendous impact on chemical biology, allowing the study of numerous biological processes directly in complex systems. However, despite the fact that multiple biocompatible reactions have been developed in the past decade, very few work well in living mice. Here we report that D-cysteine and 2-cyanobenzothiazoles can selectively react with each other in vivo to generate a luciferin, substrate for firefly luciferase. The success of this "split luciferin" ligation reaction has important implications for both in vivo imaging and biocompatible labeling strategies. First, the production of a luciferin substrate can be visualized in a live mouse by bioluminescence imaging (BLI) and furthermore allows interrogation of targeted tissues using a "caged" luciferin approach. We therefore applied this reaction to the real-time noninvasive imaging of apoptosis associated with caspase 3/7. Caspase-dependent release of free D-cysteine from the caspase 3/7 peptide substrate Asp-Glu-Val-Asp-D-Cys (DEVD-(D-Cys)) allowed selective reaction with 6-amino-2-cyanobenzothiazole (NH2-CBT) in vivo to form 6-amino-D-luciferin with subsequent light emission from luciferase. Importantly, this strategy was found to be superior to the commercially available DEVD-aminoluciferin substrate for imaging of caspase 3/7 activity. Moreover, the split luciferin approach enables the modular construction of bioluminogenic sensors, where either or both reaction partners could be caged to report on multiple biological events. Lastly, the luciferin ligation reaction is 3 orders of magnitude faster than Staudinger ligation, suggesting further applications for both bioluminescence and specific molecular targeting in vivo.

Amer Chemical Soc2013

Analysis of the Cytoprotective Role of alpha-Crystallins in Cell Survival and Implication of the alpha A-Crystallin C-Terminal Extension Domain in Preventing Bax-Induced Apoptosis

Séverine Hamann

Public Library of Science2013