These results unveil a novel regulatory pathway that links mitochondrial activity and mitochondrial oxidative stress protective systems. In addition, they suggest that PGC-1alpha could play a crucial protective role in vascular complications of diabetes, where the mitochondrial metabolism of glucose has been shown to result in oxidative stress and vascular endothelial cell dysfunction.

The nucleocapsid (N) protein is the only phosphorylated structural protein of the coronavirus Transmissible gastroenteritis virus (TGEV). The phosphorylation state and intracellular distribution of TGEV N protein in infected cells were characterized by a combination of techniques including: (i) subcellular fractionation and analysis of tryptic peptides by two-dimensional nano-liquid chromatography, coupled to ion-trap mass spectrometry; (ii) tandem mass-spectrometry analysis of N protein resolved by SDS-PAGE; (iii) Western blotting using two specific antisera for phosphoserine-containing motifs; and (iv) confocal microscopy. A total of four N protein-derived phosphopeptides were detected in mitochondria-Golgi-endoplasmic reticulum-Golgi intermediate compartment (ERGIC)-enriched fractions, including N-protein phosphoserines 9, 156, 254 and 256. Confocal microscopy showed that the N protein found in mitochondria-Golgi-ERGIC fractions localized within the Golgi-ERGIC compartments and not with mitochondria. Phosphorylated N protein was also present in purified virions, containing at least phosphoserines 156 and 256. Coronavirus N proteins showed a conserved pattern of secondary structural elements, including six b-strands and four a-helices. Whilst serine 9 was present in a non-conserved domain, serines 156, 254 and 256 were localized close to highly conserved secondary structural elements within the central domain of coronavirus N proteins. Serine 156 was highly conserved, whereas no clear homologous sites were found for serines 254 and 256 for other coronavirus N proteins. INTRODUCTIONTransmissible gastroenteritis virus (TGEV) is a member of the Coronaviridae, a family of enveloped, positive-strand RNA viruses divided into three groups based on antigenic and genetic criteria (Enjuanes et al., 2000a; González et al., 2003). Group 1, to which TGEV belongs, includes members infecting human and NL63], porcine [TGEV and Porcine epidemic diarrhea virus (PEDV)], canine [Canine coronavirus (CCoV)] and feline [Feline coronavirus (FCoV)] species. All coronaviruses contain at least four structural proteins. The spike (S), membrane (M) and envelope (E) proteins are embedded in the virus envelope. The nucleocapsid (N) protein binds to the RNA genome forming the helical nucleocapsid (Sturman et al., 1980), which is arranged in TGEV virions as a spherical core by binding to the M protein (Escors et al., 2001a, b;Narayanan et al., 2000). Coronavirus N proteins are highly basic with a molecular mass ranging from 40 to 63 kDa, depending on the species and strain (Cologna & Hogue, 1998;Cologna et al., 2000;Nelson et al., 2000;Robbins et al., 1986;Stohlman et al., 1988). The N protein binds to the approximately 27-31 kb coronavirus RNA genome forming the helical nucleocapsid (Escors et al., 2001a;Kuo & Masters, 2002;Narayanan et al., 2000;Risco et al., 1998;Salanueva et al., 1999;Sturman et al., 1980) and is also involved in virus replication (Almazán et al., 2004;Bost et al., 2001;Chang & Brian, 1996; Prentice et al., 2004;Yount...

IntroductionThe mammalian adult heart maintains a continuous, low cardiomyocyte turnover rate throughout life. Although many cardiac stem cell populations have been studied, the natural source for homeostatic repair has not yet been defined. The Polycomb protein BMI1 is the most representative marker of mouse adult stem cell systems. We have evaluated the relevance and role of cardiac Bmi1+ cells in cardiac physiological homeostasis.MethodsBmi1CreER/+;Rosa26YFP/+ (Bmi1-YFP) mice were used for lineage tracing strategy. After tamoxifen (TM) induction, yellow fluorescent protein (YFP) is expressed under the control of Rosa26 regulatory sequences in Bmi1+ cells. These cells and their progeny were tracked by FACS, immunofluorescence and RT-qPCR techniques from 5 days to 1 year.ResultsFACS analysis of non-cardiomyocyte compartment from TM-induced Bmi1-YFP mice showed a Bmi1+-expressing cardiac progenitor cell (Bmi1-CPC: B-CPC) population, SCA-1 antigen-positive (95.9 ± 0.4 %) that expresses some stemness-associated genes. B-CPC were also able to differentiate in vitro to the three main cardiac lineages. Pulse-chase analysis showed that B-CPC remained quite stable for extended periods (up to 1 year), which suggests that this Bmi1+ population contains cardiac progenitors with substantial self-maintenance potential. Specific immunostaining of Bmi1-YFP hearts serial sections 5 days post-TM induction indicated broad distribution of B-CPC, which were detected in variably sized clusters, although no YFP+ cardiomyocytes (CM) were detected at this time. Between 2 to 12 months after TM induction, YFP+ CM were clearly identified (3 ± 0.6 % to 6.7 ± 1.3 %) by immunohistochemistry of serial sections and by flow cytometry of total freshly isolated CM. B-CPC also contributed to endothelial and smooth muscle (SM) lineages in vivo.ConclusionsHigh Bmi1 expression identifies a non-cardiomyocyte resident cardiac population (B-CPC) that contributes to the main lineages of the heart in vitro and in vivo.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0196-9) contains supplementary material, which is available to authorized users.

Number of molecules and Brightness (N&B) has been proposed for measuring the molecular brightness and number of fluorophores in time-sequence of images, in live cells. If the fluorescently tagged-proteins are mobile in the illumination volume, the stoichiometry of their oligomers can be derived from the increase of the brightness of the fluorescent dyes due to clustering. We examine aspects concerning extra-fluctuation effects induced by cell shifts and photobleaching, which yield large overestimates of the clusters size and sub-unit counts. We develop an offline corrective approach consisting in frame re-alignment and boxcar filtering for recovering precision of the analysis. Using simulations we derive general criteria for approaching this analysis, and assess the application limits of the corrective procedure. We tested the approach in extreme experimental conditions (few pixels, large extra-variance perturbations), in which we analyzed the minimal increases of brightness as that expected between a monomeric and dimeric GPI-mEGFP constructs. We show how most of the perturbing effects can be abolished, and obtain the correct the brightness of GPI-mEGFP monomers and dimers.

Peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α) is a regulator of mitochondrial oxidative metabolism and reactive oxygen species (ROS) homeostasis that is known to be inactivated in diabetic subjects. This study aimed to investigate the contribution of PGC-1α inactivation to the development of oxygen-induced retinopathy. We analyzed retinal vascular development in PGC-1α(-/-) mice. Retinal vasculature of PGC-1α(-/-) mice showed reduced pericyte coverage, a de-structured vascular plexus, and low perfusion. Exposure of PGC-1α(-/-) mice to hyperoxia during retinal vascular development exacerbated these vascular abnormalities, with extensive retinal hemorrhaging and highly unstructured areas as compared with wild-type mice. Structural analysis demonstrated a reduction in membrane-bound VE-cadherin, which was suggestive of defective intercellular junctions. Interestingly, PGC-1α(-/-) retinas showed a constitutive activation of the VEGF-A signaling pathway. This phenotype could be partially reversed by antioxidant administration, indicating that elevated production of ROS in the absence of PGC-1α could be a relevant factor in the alteration of the VEGF-A signaling pathway. Collectively, our findings suggest that PGC-1α control of ROS homeostasis plays an important role in the regulation of de novo angiogenesis and is required for vascular stability.