Suchergebnisse

The neuronal long isoform of Fas Apoptotic Inhibitory Molecule (FAIM-L) protects from death receptor (DR)-induced apoptosis, yet its mechanism of protection remains unknown. Here, we show that FAIM-L protects rat neuronal Type II cells from Fas-induced apoptosis. XIAP has previously emerged as a molecular discriminator that is upregulated in Type II and downregulated in Type I apoptotic signaling. We demonstrate that FAIM-L requires sustained endogenous levels of XIAP to protect Type II cells as well as murine cortical neurons from Fas-induced apoptosis. FAIM-L interacts with the BIR2 domain of XIAP through an IAP-binding motif, the mutation of which impairs the antiapoptotic function of FAIM-L. Finally, we report that FAIM-L inhibits XIAP auto-ubiquitinylation and maintains its stability, thus conferring protection from apoptosis. Our results bring new understanding of the regulation of endogenous XIAP by a DR antagonist, pointing out at FAIM-L as a promising therapeutic tool for protection from apoptosis in pathological situations where XIAP levels are decreased. ; This work was funded by the Spanish Government Ministerio de Sanidad y Consumo (Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, CB06/05/1104 to J.X.C.), Ministerio de Economía y Competitividad (SAF2010–19953 to J.X.C.; SAF2012–31485 to V.J.Y.), Instituto de Salud Carlos III (CP11/00052 to M.F.S.), and the Generalitat de Catalunya (Suport als Grups de Recerca Consolidats 2009SGR346). F.M.-F. and L.P.-F. are supported by postgraduate fellowships from the Spanish Government Ministerio de Educación y Ciencia. J.U. is supported by a postgraduate fellowship from the Generalitat de Catalunya. R.S.M. and V.J.Y. were under the Juan de la Cierva and the Ramon y Cajal programs, respectively, from the Ministerio de Educación y Ciencia (Spain), cofinanced by the European Social Fund. M.F.S. is under the Miguel Servet program from the Instituto de Salud Carlos III and cofinanced by the European Regional Development Fund.

Death receptors (DRs) and their ligands are expressed in developing nervous system. However, neurons are generally resistant to death induction through DRs and rather their activation promotes neuronal outgrowth and branching. These results suppose the existence of DRs antagonists expressed in the nervous system. Fas apoptosis inhibitory molecule (FAIMS ) was first identified as a Fas antagonist in B-cells. Soon after, a longer alternative spliced isoform with unknown function was identified and named FAIML. FAIMS is widely expressed, including the nervous system, and we have shown previously that it promotes neuronal differentiation but it is not an anti-apoptotic molecule in this system. Here, we demonstrate that FAIML is expressed specifically in neurons, and its expression is regulated during the development. Expression could be induced by NGF through the extracellular regulated kinase pathway in PC12(pheochromocytoma cell line) cells. Contrary to FAIMS , FAIML does not increase the neurite outgrowth induced by neurotrophins and does not interfere with nuclear factor ĸB pathway activation as FAIMS does. Cells overexpressing FAIML are resistant to apoptotic cell death induced by DRs such as Fas or tumor necrosis factor R1. Reduction of endogenous expression by small interfering RNA shows that endogenousFAIML protects primary neurons from DR-induced cell death. The detailed analysis of this antagonism shows thatFAIML can bind to Fas receptor and prevent the activation of the initiator caspase-8 induced by Fas. In conclusion, our results indicate that FAIML could be responsible for maintaining initiator caspases inactive after receptor engagement protecting neurons from the cytotoxic action of death ligands. ; This work was supported by Spanish Government "Ministerio de Sanidad y Consumo" (contract number PI020051, PI04/2364, Redes Temáticas de Investigación Cooperativa, and CiberNed), Fundació La Caixa (Ayudas a la Investigación en Enfermedades Neurodegenerativas 02/055-00), Ministerio de Educacio´n y Ciencia (SAF-2005- 0176), and Generalitat de Catalunya (Suport als Grups de Recerca Consolidats and Distinció a Joves Investigadors). M.F.S., C.S., and M.J.P.-G. were supported by a postgraduate fellowship from the Spanish Government, Ministerio de Educación y Ciencia and Fondo de Investigación Sanitaria, respectively. R.G. holds a postgraduate fellowship from the Department d'Universitat, Recerca i Societat de la Informació (Generalitat de Catalunya) and Fons Social Europeu. N.B. is the recipient of a postgraduate fellowship from the Gobierno Vasco. V.J.Y. was under a Beatriu de Pino´s contract from Generalitat de Catalunya.