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This is an open-access article distributed under the terms of the Creative Commons Attribution License.-- et al. ; Sei1 is a positive regulator of proliferation that promotes the assembly of Cdk4-cyclin D complexes and enhances the transcriptional activity of E2f1. The potential oncogenic role of Sei1 is further suggested by its overexpression in various types of human cancers. To study the role of Sei1, we have generated a mouse line deficient for this gene. Sei1-null fibroblasts did not show abnormalities regarding proliferation or susceptibility to neoplastic transformation, nor did we observe defects on Cdk4 complexes or E2f activity. Sei1-null mice were viable, did not present overt pathologies, had a normal lifespan, and had a normal susceptibility to spontaneous and chemically-induced cancer. Pancreatic insulin-producing cells are known to be particularly sensitive to Cdk4-cyclin D and E2f activities, and we have observed that Sei1 is highly expressed in pancreatic islets compared to other tissues. Interestingly, Sei1-null mice present lower number of islets, decreased beta-cell area, impaired insulin secretion, and glucose intolerance. These defects were associated to nuclear accumulation of the cell-cycle inhibitors p21(Cip1) and p27(Kip1) in islet cells. We conclude that Sei1 plays an important role in pancreatic beta-cells, which supports a functional link between Sei1 and the core cell cycle regulators specifically in the context of the pancreas. ; Work in the laboratory of M.S. is funded by the Centro Nacional de Investigaciones Oncológicas (CNIO) and by grants from the Spanish Ministry of Science (SAF and CONSOLIDER), the Regional Government of Madrid (GsSTEM), the European Union (PROTEOMAGE), the European Research Council (ERC), and the ''Marcelino Botin'' Foundation. Work in the laboratory of A.M.V. was funded by the Ministry of Science (BFU2008-02420) and by the Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM). ; Peer reviewed

15 páginas, 7 figuras.-- et al. ; Bacterial LPS (endotoxin) has been implicated in the pathogenesis of acute liver disease through its induction of the proinflammatory cytokine TNF-α. TNF-α is a key determinant of the outcome in a well-established mouse model of acute liver failure during septic shock. One possible mechanism for regulating TNF-α expression is through the control of protein elongation during translation, which would allow rapid cell adaptation to physiological changes. However, the regulation of translational elongation is poorly understood. We found that expression of p38γ/δMAPK proteins is required for the elongation of nascent TNF-α protein in macrophages. The MKK3/6-p38γ/δpathway mediated an inhibitory phosphorylation of eukaryotic elongation factor 2 (eEF2) kinase, which in turn promoted eEF2 activation (dephosphorylation) and subsequent TNF-α elongation. These results identify a new signaling pathway that regulates TNF-α production in LPS-induced liver damage and suggest potential cell-specific therapeutic targets for liver diseases in which TNF-α production is involved. ; G. Sabio is an investigator of the Ramón y Cajal Program and a recipient of a Principe de Girona Impulsa award. R.J. Davis is an investigator of the Howard Hughes Medical Institute. Á. Verdugo is a recipient of a Madrid Regional Government fellowship. E. Manieri is a fellow of the La Caixa Foundation Á. González-Rodríguez was supported by CIBERDEM (ISCIII, Spain). This work was funded by the following grants: ERC 260464, EFSD 2030, MICINN SAF2010-19347, and Comunidad de Madrid S2010/BMD-2326 (to G. Sabio:); MICINN SAF2011-27330 (to P. Martin); and MICINN SAF2012-3328 (to Á. Valverde). The CNIC is supported by the Ministry of Economy and Competitiveness and the Pro-CNIC Foundation. ; Peer Reviewed

[Objectives]: Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in Western countries. Protein tyrosine phosphatase 1B (PTP1B), a negative modulator of insulin and cytokine signaling, is a therapeutic target for type 2 diabetes and obesity. We investigated the impact of PTP1B deficiency during NAFLD, particularly in non-alcoholic steatohepatitis (NASH). [Methods]: NASH features were evaluated in livers from wild-type (PTP1BWT) and PTP1B-deficient (PTP1BKO) mice fed methionine/choline-deficient diet (MCD) for 8 weeks. A recovery model was established by replacing MCD to chow diet (CHD) for 2–7 days. Non-parenchymal liver cells (NPCs) were analyzed by flow cytometry. Oval cells markers were measured in human and mouse livers with NASH, and in oval cells from PTP1BWT and PTP1BKO mice. [Results]: PTP1BWT mice fed MCD for 8 weeks exhibited NASH, NPCs infiltration, and elevated Fgf21, Il6 and Il1b mRNAs. These parameters decreased after switching to CHD. PTP1B deficiency accelerated MCD-induced NASH. Conversely, after switching to CHD, PTP1BKO mice rapidly reverted NASH compared to PTP1BWT mice in parallel to the normalization of serum triglycerides (TG) levels. Among NPCs, a drop in cytotoxic natural killer T (NKT) subpopulation was detected in PTP1BKO livers during recovery, and in these conditions M2 macrophage markers were up-regulated. Oval cells markers (EpCAM and cytokeratin 19) significantly increased during NASH only in PTP1B-deficient livers. HGF-mediated signaling and proliferative capacity were enhanced in PTP1BKO oval cells. In NASH patients, oval cells markers were also elevated. [Conclusions]: PTP1B elicits a dual role in NASH progression and reversion. Additionally, our results support a new role for PTP1B in oval cell proliferation during NAFLD. ; This work was funded by SAF2015-65267-R (MINECO/FEDER), CIBERdem (ISCIII, Spain), INFLAMES (ISCIII PIE14/00045, co-funded by ERDF, "Investing in your future") to A.M.V; IJCI-2014-19381 (MINECO/FEDER) to P.R and A.M.V; CP14/00181 and PI16/00823 (ISCIII/FEDER) and CIBERehd (ISCIII, Spain) to A.G-R; BFU2015-65937-R (MINECO/FEDER), 67-2015 (Department of Health, Navarra Government) and CIBERobn (ISCIII, Spain) to M.J.M; SAF2015-69145-R (MINECO/FEDER) to A.S. A.A. was recipient of a Marie Curie ESR contract from IT-LIVER (Marie Curie Action of the FP7-2012, grant agreement 316549). We also acknowledge the European Union, project H2020-MSCA-ITN TREATMENT Grant Agreement number: 721236. ; Peer Reviewed