All-trans-retinoic acids (ATRA) is one of the biologically active metabolites of vitamin A which plays an important role in cell differentiation and proliferation (MB. Reeves et al. 2007, Science). The molecular basis of its action has not been fully elucidated. It was previously shown (F. Papa et al. 2007, Int.J.Immun.Pharm.) that ATRA treatment of normal human keratinocytes resulted in growth suppression, increase of complex I content and reduction of the NADH-UQ oxidoreductase enzymatic activity. These effects were associated with enhanced level of GRIM-19. We found that induction of cAMP-PKA signalling, by dibutyryl cyclic AMP or okadaic acid, restores the complex I activity inhibited by ATRA, indicating an interplay between ATRA and PKA signal transduction on regulation of cellular bioenergetics. Mitochondrial proteome has to be considered as a non-static entity, that shows characteristic changes according to the functional state of the cell. To monitor the effect of ATRA on mitochondria keratinocytes protein profile a widesearch proteomic approach was used. In ATRA treated cells, a large number of mitochondrial proteins, were found to be up or down expressed with respect to control cells. In particular ATRA cell-treatment appeared to affect proteins which are synthesized in very low amount, as the case of regulatory proteins. Two proteins spots, down regulated in mitochondria of ATRA treated keratinocytes, were identified by mass spectrometry analysis as ATP synthase beta subunit, component of complex V, and protein disulfide-isomerase A6. These results indicate an effect of ATRA on the expression of mitochondrial OXPHOS complexes.

Introduction: Sorafenib is currently the only approved therapy in hepatocellular carcinoma (HCC). Alternative first- and second-line treatments are a significant unmet medical need, and several biologic agents have been tested in recent years, with poor results. Therefore, angiogenic pathways and the cytokine cascade remain possible targets in HCC. Recent studies suggest a role of epigenetic processes, associated with the initiation and development of HCC. In this field, DNA methylation, micro-RNAs (miRNAs) and tumor microenvironment cells became a possible new target for HCC treatment. Areas covered: This review explains the possible role of DNA methylation and histone deacetylase inhibitors as predictive biomarkers and target therapy, the extensive world of the promising miRNA blockade strategy, and the recent strong evidence of correlation between HCC tumors and peritumoral stroma cells. The literature and preclinic/clinic data were obtained through an electronic search. Expert opinion: Future research should aim to understand how best to identify patient groups that would benefit most from the prescribed therapy. To overcome the therapeutic stranding of HCC, a possible way out from the current therapeutic tunnel might be to evaluate the major epigenetic and genetic processes involved in HCC carcinogenesis, not underestimating the tumor microenvironment and its actors (angiogenesis, immune system, platelets). We are only at the start of a long journey towards the elucidation of HCC molecular pathways as therapeutic targets. Yet, currently this path appears to be the only one to cast some light at the end of the tunnel. © 2015 Taylor & Francis.

The NDUFS4 subunit of complex I of the mammalian respiratory chain has a fully conserved carboxy-terminus with a canonical RVSTK phosphorylation site. Immunochemical analysis with specific antibodies shows that the serine in this site of the protein is natively present in complex I in both the phosphorylated and non-phosphorylated state. Two-dimensional IEF/SDS-PAGE electrophoresis, (32)P labelling and immunodetection show that "in vitro" PKA phosphorylates the serine in the C-terminus of the NDUFS4 subunit in isolated bovine complex I. (32)P labelling and TLC phosphoaminoacid mapping show that PKA phosphorylates serine and threonine residues in the purified heterologous human NDUFS4 protein.

In mammals, complex I (NADH-ubiquinone oxidoreductase) of the mitochondrial respiratory chain has 31 supernumerary subunits in addition to the 14 conserved from prokaryotes to humans. Multiplicity of structural protein components, as well as of biogenesis factors, makes complex I a sensible pace-maker of mitochondrial respiration. The work reviewed here shows that the cAMP/PKA pathway regulates the biogenesis, assembly and catalytic activity of complex I and mitochondrial oxygen superoxide production. The structural, functional and regulatory complexity of complex I, renders it particularly vulnerable to genetic and sporadic pathological factors. Complex I dysfunction has, indeed, been found, to be associated with several human diseases. Knowledge of the pathogenetic mechanisms of these diseases can help to develop new therapeutic strategies. (C) 2011 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.