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[EN] Ceria nanoparticles are cell compatible antioxidants whose activity can be enhanced by gold deposition and by surface functionalization with positive triphenylphosphonium units to selectively target the mitochondria. The antioxidant properties of these nanoparticles can serve as the basis of a new strategy for the treatment of several disorders exhibiting oxidative stress, such as cancer, diabetes or Alzheimer's disease. However, all of these pathologies require a specific antioxidant according with their mechanism to remove oxidant species excess in cells and diminish their effect on mitochondrial function. The mechanism through which ceria nanoparticles neutralize oxidative stress and their effect on mitochondrial function have not been characterized yet. In the present study, the mitochondria antioxidant effect of ceria and ceria-supported gold nanoparticles, with or without triphenylphosphonium functionalization, was assessed in HeLa cells. The effect caused by ceria nanoparticles on mitochondria function in terms of mitochondrial membrane potential (Delta Psi m), adenosine triphosphate (ATP) production, nuclear respiratory factor 1 (NRF1) and nuclear factor erythroid-2 like 1 (NFE2L1) was reversed by the presence of gold. Furthermore, this effect was enhanced when nanoparticles were functionalized with triphenylphosphonium. Our study illustrates how the mitochondrial antioxidant effect induced by ceria nanoparticles can be modulated by the presence of gold. ; This research was funded by Carlos III Health Institute and the European Regional Development Fund, grant number CP13/00252 and PI16/1083; the Catalonian Agency for Management of University and Research Grants, grant number 2017SGR1303; the Ministry of Education of the Valencian Regional Government, grant number PROMETEO/2019/027, The Foundation for the Promotion of Health and Biomedical Research of Valencia Region, grant number Nanobetes2. ; Gutiérrez-Carcedo, P.; Navalón Oltra, S.; Simó, R.; Setoain, X.; Aparicio-Gómez, C.; Abasolo, I.; Victor, ...

The actin cytoskeleton coordinates the organization of signaling microclusters at the immune synapse (IS); however, the mechanisms involved remain poorly understood. We show here that nitric oxide (NO) generated by endothelial nitric oxide synthase (eNOS) controls the coalescence of protein kinase C-theta (PKC-theta) at the central supramolecular activation cluster (c-SMAC) of the IS. eNOS translocated with the Golgi to the IS and partially colocalized with F-actin around the c-SMAC. This resulted in reduced actin polymerization and centripetal retrograde flow of beta-actin and PKC-theta from the lamellipodium-like distal (d)-SMAC, promoting PKC-theta. activation. Furthermore, eNOS-derived NO S-nitrosylated beta-actin on Cys374 and impaired actin binding to profilin-1 (PFN1), as confirmed with the transnitrosylating agent S-nitroso-L-cysteine (Cys-NO). The importance of NO and the formation of PFN1-actin complexes on the regulation of PKC-theta. was corroborated by overexpression of PFN1- and actin-binding defective mutants of beta-actin (C374S) and PFN1 (H119E), respectively, which reduced the coalescence of PKC-theta. at the c-SMAC. These findings unveil a novel NO-dependent mechanism by which the actin cytoskeleton controls the organization and activation of signaling microclusters at the IS. ; Institute de Salud Carlos III (ISCIII, Spanish Government) (grant number PI10/02136) to J.M.S. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ERC (grant number ERC-2011-AdG294340-GENTRIS) to F.S.M. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. MINECO/FEDER (grant number SAF2015-69396-R) to J.M.S. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. MINECO (grant number B102015-67580-P) to J.V. The funder had no role in study design, data collection and analysis, decision to publish, or ...