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  • br Materials and methods br Results br Discussion Although

    2019-07-24


    Materials and methods
    Results
    Discussion Although the exact mechanism responsible for NAFLD development and progression is still poorly understood, oxidative stress could be the “second hit” triggering the transition from steatosis to steatohepatitis, and promoting hepatic damage, Okadaic acid and fibrosis [39,40]. We investigated whether treatment with vitamin E could prevent the development of NASH in a mouse model of reduced PC synthesis. In summary, we observed improved VLDL-TG secretion from the liver, and normalization of cholesterol metabolism, but no reduction in hepatic TG upon vitamin E supplementation in HFD-fed Pemt mice. Nevertheless, vitamin E supplementation efficiently prevented hepatic oxidative stress, inflammation and fibrosis, Moreover, aberrant ceramide metabolism in Pemt mice was restored with vitamin E supplementation. Thus, vitamin E supplementation prevented the progression from simple steatosis to steatohepatitis in mice lacking PEMT.
    Funding sources This research was supported by a grant from the Canadian Institutes of Health Research (MOP 5182 to D.E.V., R.L.J and J.N.V.), grants IT-1106-16 from “Departamento de Educación, Universidades e Investigación del Gobierno Vasco” (GV/EJ, Spain) and SAF2016-79695-R from “Ministerio de Economía y Competitividad” (Madrid, Spain) to A.G.M., and funds from the Smithgall Institute Chair for Molecular Cell Biology at Georgia Tech (S.E.K. and A.H.M.).
    Author contributions
    Disclosures
    Transparency document
    Introduction Metastasis is the primary cause of death in cancer patients. Although some cancer cell properties involved in metastatic progression (such as local invasion, intravasation, and organ colonization) have been identified [[1], [2], [3]], the molecular mechanisms orchestrating both the determination of a particular malignant phenotype [4] and a specific metastatic organotropism [2] are still poorly understood. Signaling complexes are spatially and dynamically coordinated by scaffolding proteins, which allow for rapid phenotypical switches under microenvironment changes [[5], [6], [7]]. Changes in the scaffolding protein concentration, subcellular localization and/or interaction specificities can radically alter cell phenotype. This ability to reprogram cellular behavior forms the basis for cancer progression towards aggressive stages. A number of studies have identified a central role for the scaffolding protein Na+/H+ Exchanger Regulatory Factor (NHERF1) in cancer. NHERF1 is upregulated in diverse cancers where its level of expression correlates with aggressive stage and poor prognosis [[8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]]. NHERF1 contains two tandem PDZ domains and recruits membrane receptors and transporters, cytoplasmic cytoskeleton and signaling proteins into functional complexes that regulate cell processes that are relevant to cancer progression [20], including cell proliferation [12,16,17,[21], [22], [23], [24]], survival [25], apoptosis [26], migration and invasion [8,27]. NHERF1 also controls growth factor receptor trafficking/function [12,23,28,29] and is involved in the inhibition of both growth and invasion induced by the EGFR inhibitors Gefitinib and Erlotinib [12,23]. In breast cancer cells, NHERF1 has been shown to organize molecular pathways, through its PDZ domains, that differentially determine the programs that regulate the expression of in vitro tumor phenotypes [30]. This PDZ domain-dependent reprogramming capacity of NHERF1 was postulated to be regulated in vivo by the differential phosphorylation of different serine residues [30]. Indeed, changes in phosphorylation state by cell- and context- specific kinases and phosphatases is one of the major mechanisms for regulating protein activities and functions, and NHERF1 is phosphorylated both constitutively and by (patho)physiological stimuli. The phosphorylation of serines 279 and 301 have been shown to regulate cell cycle [31,32], cell morphology, actin cytoskeleton organization and cell adherence to the extracellular matrix (ECM) [32] and the stability/half-life of NHERF1 itself [33].