Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
High sea surface temperature accompanied by high levels of solar irradiance is responsible for the disruption of the symbiosis between cnidarians and their symbiotic dinoflagellates from the genus Symbiodinium. This phenomenon, known as coral bleaching, is one of the major threats affecting coral reefs around the world. Because an important molecular trigger to bleaching appears related to the production of reactive oxygen species (ROS), it is critical to understand the function of the antioxidant network of Symbiodinium species. In this study we investigated the response of two Symbiodinium species, from contrasting environments, to a chemically induced oxidative stress. ROS produced during this oxidative burst reduced photosynthesis by 30 to 50% and significantly decreased the activity of superoxide dismutase. Lipid peroxidation levels and carotenoid concentrations, especially diatoxanthin, confirm that these molecules act as antioxidants and contribute to the stabilization of membrane lipids. The comparative analysis between the two Symbiodinium species allowed us to highlight that Symbiodinium sp. clade A temperate was more tolerant to oxidative stress than the tropical S. kawagutii clade F. These differences are very likely a consequence of adaptation to their natural environment, with the temperate species experiencing conditions of temperature and irradiance much more variable and extreme.
ISSN: 0140-7791

hal-01546161
https://hal.archives-ouvertes.fr/hal-01546161
DOI : 10.1111/pce.12825

Éditeur(s) : HAL CCSD Portland Press
Résumé : International audience
Lutheran (Lu) blood group and Basal Cell Adhesion Molecule (BCAM) antigens both reside on two glycoprotein (gp) isoforms, Lu and Lu(v13), that differ by the size of their cytoplasmic tail. They are receptors of laminin-10/11 and are expressed in red blood cells (RBCs), epithelial cells of multiple tissues and vascular endothelial cells. To gain more insights into the biological function of Lu/BCAM gps, we looked for potential partners of their cytoplasmic tail. We isolated Ubc9 (Ubiquitin-conjugating enzyme 9) protein by screening a human kidney library using the yeast two-hybrid system. Lu/Ubc9 interaction was validated by GST pull-down and co-immunoprecipitation experiments. Endogenous Ubc9 formed a complex with endogenous or recombinant Lu gp in A498 and MDCK epithelial cells, respectively. Substitution of lysine 585 by alanine in the Lu gp, abolished in vitro and ex vivo interaction of Lu gp with Ubc9 protein. Lu K585A mutant transfected in MDCK cells exhibited a normal basolateral membrane expression but was overexpressed at the surface of polarized MDCK cells as compared to wild-type Lu. Pulse-chase experiments showed extended half-life of Lu K585A gp at the plasma membrane, suggesting an impaired endocytosis of this mutant leading to protein accumulation at the membrane. Furthermore, we showed that the ability of MDCK-Lu K585A cells to spread on immobilized laminin was dramatically decreased. Our data supports a physiological role for the direct interaction between Lu gp and Ubc9 protein, and reveals a role for this enzyme in regulating the stability of Lu gp at the cell membrane.
ISSN: 0264-6021

hal-00478614
https://hal.archives-ouvertes.fr/hal-00478614
https://hal.archives-ouvertes.fr/hal-00478614/document
https://hal.archives-ouvertes.fr/hal-00478614/file/PEER_stage2_10.1042%252FBJ20060861.pdf
DOI : 10.1042/BJ20060861

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
CYLD is a tumour suppressor gene mutated in familial cylindromatosis, a genetic disorder leading to the development of skin appendage tumours. It encodes a deubiquitinating enzyme that removes Lys63- or linear-linked ubiquitin chains. CYLD was shown to regulate cell proliferation, cell survival and inflammatory responses, through various signalling pathways. Here we show that CYLD localizes at centrosomes and basal bodies via interaction with the centrosomal protein CAP350 and demonstrate that CYLD must be both at the centrosome and catalytically active to promote ciliogenesis independently of NF-κB. In transgenic mice engineered to mimic the smallest truncation found in cylindromatosis patients, CYLD interaction with CAP350 is lost disrupting CYLD centrosome localization, which results in cilia formation defects due to impairment of basal body migration and docking. These results point to an undiscovered regulation of ciliogenesis by Lys63 ubiquitination and provide new perspectives regarding CYLD function that should be considered in the context of cylindromatosis.
ISSN: 2041-1723

hal-01063915
https://hal.archives-ouvertes.fr/hal-01063915
DOI : 10.1038/ncomms5585
PUBMED : 25134987