Neurogenesis Drives Stimulus Decorrelation in a Model of the Olfactory Bulb

The reshaping and decorrelation of similar activity patterns by neuronal networks can enhance their discriminability, storage, and retrieval. How can such networks learn to decorrelate new complex patterns, as they arise in the olfactory system? Using a computational network model for the dominant neural populations of the olfactory bulb we show that fundamental aspects of the adult neurogenesis observed in the olfactory bulb -- the persistent addition of new inhibitory granule cells to the network, their activity-dependent survival, and the reciprocal character of their synapses with the principal mitral cells -- are sufficient to restructure the network and to alter its encoding of odor stimuli adaptively so as to reduce the correlations between the bulbar representations of similar stimuli. The decorrelation is quite robust with respect to various types of perturbations of the reciprocity. The model parsimoniously captures the experimentally observed role of neurogenesis in perceptual learning and the enhanced response of young granule cells to novel stimuli. Moreover, it makes specific predictions for the type of odor enrichment that should be effective in enhancing the ability of animals to discriminate similar odor mixtures

Activin B Promotes Epithelial Wound Healing In Vivo through RhoA-JNK Signaling Pathway

Background: Activin B has been reported to promote the proliferation and migration of keratinocytes in vitro via the RhoA-JNK signaling pathway, whereas its in vivo role and mechanism in wound healing process has not yet been elucidated. Principal Findings: In this study, we explored the potential mechanism by which activin B induces epithelial wound healing in mice. Recombinant lentiviral plasmids, with RhoA (N19) and RhoA (L63) were used to infect wounded KM mice. The wound healing process was monitored after different treatments. Activin B-induced cell proliferation on the wounded skin was visualized by electron microscopy and analyzed by 59-bromodeoxyuridine (BrdU) incorporation assay. Protein expression of p-JNK or p-cJun was determined by immunohistochemical staining and immunoblotting analysis. Activin B efficiently stimulated the proliferation of keratinocytes and hair follicle cells at the wound area and promoted wound closure. RhoA positively regulated activin B-induced wound healing by up-regulating the expression of p-JNK and p-cJun. Moreover, suppression of RhoA activation delayed activin B-induced wound healing, while JNK inhibition recapitulated phenotypes of RhoA inhibition on wound healing. Conclusion: These results demonstrate that activin B promotes epithelial wound closure in vivo through the RhoA-Rock

Tuberous Sclerosis Complex-1 Deficiency Attenuates Diet-Induced Hepatic Lipid Accumulation

Non-alcoholic fatty liver disease (NAFLD) is causally linked to type 2 diabetes, insulin resistance and dyslipidemia. In a normal liver, insulin suppresses gluconeogenesis and promotes lipogenesis. In type 2 diabetes, the liver exhibits selective insulin resistance by failing to inhibit hepatic glucose production while maintaining triglyceride synthesis. Evidence suggests that the insulin pathway bifurcates downstream of Akt to regulate these two processes. Specifically, mTORC1 has been implicated in lipogenesis, but its role on hepatic steatosis has not been examined. Here, we generated mice with hepatocyte-specific deletion of Tsc1 to study the effects of constitutive mTORC1 activation in the liver. These mice developed normally but displayed mild hepatomegaly and insulin resistance without obesity. Unexpectedly, the Tsc1-null livers showed minimal signs of steatosis even under high-fat diet condition. This ‘resistant’ phenotype was reversed by rapamycin and could be overcome by the expression of Myr-Akt. Moreover, rapamycin failed to reduce hepatic triglyceride levels in models of steatosis secondary to Pten ablation in hepatocytes or high-fat diet in wild-type mice. These observations suggest that mTORC1 is neither necessary nor sufficient for steatosis. Instead, Akt and mTORC1 have opposing effects on hepatic lipid accumulation such that mTORC1 protects against diet-induced steatosis. Specifically, mTORC1 activity induces a metabolic shift towards fat utilization and glucose production in the liver. These findings provide novel insights into the role of mTORC1 in hepatic lipid metabolism

Nuclear expression of Rac1 in cervical premalignant lesions and cervical cancer cells

<p>Abstract</p> <p>Background</p> <p>Abnormal expression of Rho-GTPases has been reported in several human cancers. However, the expression of these proteins in cervical cancer has been poorly investigated. In this study we analyzed the expression of the GTPases Rac1, RhoA, Cdc42, and the Rho-GEFs, Tiam1 and beta-Pix, in cervical pre-malignant lesions and cervical cancer cell lines.</p> <p>Methods</p> <p>Protein expression was analyzed by immunochemistry on 102 cervical paraffin-embedded biopsies: 20 without Squamous Intraepithelial Lesions (SIL), 51 Low- grade SIL, and 31 High-grade SIL; and in cervical cancer cell lines C33A and SiHa, and non-tumorigenic HaCat cells. Nuclear localization of Rac1 in HaCat, C33A and SiHa cells was assessed by cellular fractionation and Western blotting, in the presence or not of a chemical Rac1 inhibitor (NSC23766).</p> <p>Results</p> <p>Immunoreacivity for Rac1, RhoA, Tiam1 and beta-Pix was stronger in L-SIL and H-SIL, compared to samples without SIL, and it was significantly associated with the histological diagnosis. Nuclear expression of Rac1 was observed in 52.9% L-SIL and 48.4% H-SIL, but not in samples without SIL. Rac1 was found in the nucleus of C33A and SiHa cells but not in HaCat cells. Chemical inhibition of Rac1 resulted in reduced cell proliferation in HaCat, C33A and SiHa cells.</p> <p>Conclusion</p> <p>Rac1 is expressed in the nucleus of epithelial cells in SILs and cervical cancer cell lines, and chemical inhibition of Rac1 reduces cellular proliferation. Further studies are needed to better understand the role of Rho-GTPases in cervical cancer progression.</p

Murine CD4+ T Cell Responses Are Inhibited by Cytotoxic T Cell-Mediated Killing of Dendritic Cells and Are Restored by Antigen Transfer

Cytotoxic T lymphocytes (CTL) provide protection against pathogens and tumors. In addition, experiments in mouse models have shown that CTL can also kill antigen-presenting dendritic cells (DC), reducing their ability to activate primary and secondary CD8+ T cell responses. In contrast, the effects of CTL-mediated killing on CD4+ T cell responses have not been fully investigated. Here we use adoptive transfer of TCR transgenic T cells and DC immunization to show that specific CTL significantly inhibited CD4+ T cell proliferation induced by DC loaded with peptide or low concentrations of protein antigen. In contrast, CTL had little effect on CD4+ T cell proliferation induced by DC loaded with high protein concentrations or expressing antigen endogenously, even if these DC were efficiently killed and failed to accumulate in the lymph node (LN). Residual CD4+ T cell proliferation was due to the transfer of antigen from carrier DC to host APC, and predominantly involved skin DC populations. Importantly, the proliferating CD4+ T cells also developed into IFN-γ producing memory cells, a property normally requiring direct presentation by activated DC. Thus, CTL-mediated DC killing can inhibit CD4+ T cell proliferation, with the extent of inhibition being determined by the form and amount of antigen used to load DC. In the presence of high antigen concentrations, antigen transfer to host DC enables the generation of CD4+ T cell responses regardless of DC killing, and suggests mechanisms whereby CD4+ T cell responses can be amplified

Specific gene expression profiles and chromosomal abnormalities are associated with infant disseminated neuroblastoma

Background: Neuroblastoma (NB) tumours have the highest incidence of spontaneous remission, especially among the stage 4s NB subgroup affecting infants. Clinical distinction of stage 4s from lethal stage 4 can be difficult, but critical for therapeutic decisions. The aim of this study was to investigate chromosomal alterations and differential gene expression amongst infant disseminated NB subgroups. Methods: Thirty-five NB tumours from patients diagnosed at < 18 months (25 stage 4 and 10 stage 4s), were evaluated by allelic and gene expression analyses. Results: All stage 4s patients underwent spontaneous remission, only 48% stage 4 patients survived despite combined modality therapy. Stage 4 tumours were 90% near-diploid/tetraploid, 44% MYCN amplified, 77% had 1p LOH (50% 1p36), 23% 11q and/or 14q LOH (27%) and 47% had 17q gain. Stage 4s were 90% near-triploid, none MYCN amplified and LOH was restricted to 11q. Initial comparison analyses between stage 4s and 4 < 12 months tumours revealed distinct gene expression profiles. A significant portion of genes mapped to chromosome 1 (P < 0.0001), 90% with higher expression in stage 4s, and chromosome 11 (P = 0.0054), 91% with higher expression in stage 4. Less definite expression profiles were observed between stage 4s and 4 < 18m, yet, association with chromosomes 1 (P < 0.0001) and 11 (P = 0.005) was maintained. Distinct gene expression profiles but no significant association with specific chromosomal region localization was observed between stage 4s and stage 4 < 18 months without MYCN amplification. Conclusion: Specific chromosomal aberrations are associated with distinct gene expression profiles which characterize spontaneously regressing or aggressive infant NB, providing the biological basis for the distinct clinical behaviour

Adiponectin Haploinsufficiency Promotes Mammary Tumor Development in MMTV-PyVT Mice by Modulation of Phosphatase and Tensin Homolog Activities

Background: Adiponectin is an adipokine possessing beneficial effects on obesity-related medical complications. A negative association of adiponectin levels with breast cancer development has been demonstrated. However, the precise role of adiponectin deficiency in mammary carcinogenesis remains elusive. Methodology/Principal Findings: In the present study, MMTV-polyomavirus middle T antigen (MMTV-PyVT) transgenic mice with reduced adiponectin expressions were established and the stromal effects of adiponectin haploinsufficiency on mammary tumor development evaluated. In mice from both FVB/N and C57BL/6J backgrounds, insufficient adiponectin production promoted mammary tumor onset and development. A distinctive basal-like subtype of tumors, with a more aggressive phenotype, was derived from adiponectin haplodeficient MMTV-PyVT mice. Comparing with those from control MMTV-PyVT mice, the isolated mammary tumor cells showed enhanced tumor progression in re-implanted nude mice, accelerated proliferation in primary cultures, and hyperactivated phosphatidylinositol-3-kinase (PI3K)/Akt/beta-catenin signaling, which at least partly attributed to the decreased phosphatase and tensin homolog (PTEN) activities. Further analysis revealed that PTEN was inactivated by a redox-regulated mechanism. Increased association of PTEN-thioredoxin complexes was detected in tumors derived from mice with reduced adiponectin levels. The activities of thioredoxin (Trx1) and thioredoxin reductase (TrxR1) were significantly elevated, whereas treatment with either curcumin, an irreversible inhibitor of TrxR1, or adiponectin largely attenuated their activities and resulted in the re-activation of PTEN in these tumor cells. Moreover, adiponectin could inhibit TrxR1 promoter-mediated transcription and restore the mRNA expressions of TrxR1. Conclusion: Adiponectin haploinsufficiency facilitated mammary tumorigenesis by down-regulation of PTEN activity and activation of PI3K/ Akt signalling pathway through a mechanism involving Trx1/TrxR1 redox regulations. © 2009 Lam et al.published_or_final_versio

Differential regulation of mitochondrial pyruvate carrier genes modulates respiratory capacity and stress tolerance in yeast

Mpc proteins are highly conserved from yeast to humans and are necessary for the uptake of pyruvate at the inner mitochondrial membrane, which is used for leucine and valine biosynthesis and as a fuel for respiration. Our analysis of the yeast MPC gene family suggests that amino acid biosynthesis, respiration rate and oxidative stress tolerance are regulated by changes in the Mpc protein composition of the mitochondria. Mpc2 and Mpc3 are highly similar but functionally different: Mpc2 is most abundant under fermentative non stress conditions and important for amino acid biosynthesis, while Mpc3 is the most abundant family member upon salt stress or when high respiration rates are required. Accordingly, expression of the MPC3 gene is highly activated upon NaCl stress or during the transition from fermentation to respiration, both types of regulation depend on the Hog1 MAP kinase. Overexpression experiments show that gain of Mpc2 function leads to a severe respiration defect and ROS accumulation, while Mpc3 stimulates respiration and enhances tolerance to oxidative stress. Our results identify the regulated mitochondrial pyruvate uptake as an important determinant of respiration rate and stress resistance.This work was supported by Ministerio de Economia y Competitividad grant BFU2011-23326 to M.P.; A.T.-G. was supported by a JAE predoctoral grant from Consejo Superior de Investigaciones Cientificas. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Timón Gómez, A.; Proft ., MH.; Pascual-Ahuir Giner, MD. (2013). Differential regulation of mitochondrial pyruvate carrier genes modulates respiratory capacity and stress tolerance in yeast. PLoS ONE. 8(11):1-9. doi:10.1371/journal.pone.0079405S19811Murphy, M. P. (2008). How mitochondria produce reactive oxygen species. Biochemical Journal, 417(1), 1-13. doi:10.1042/bj20081386Pan, Y. (2011). Mitochondria, reactive oxygen species, and chronological aging: A message from yeast. Experimental Gerontology, 46(11), 847-852. doi:10.1016/j.exger.2011.08.007Perrone, G. G., Tan, S.-X., & Dawes, I. W. (2008). Reactive oxygen species and yeast apoptosis. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 1783(7), 1354-1368. doi:10.1016/j.bbamcr.2008.01.023Galdieri, L., Mehrotra, S., Yu, S., & Vancura, A. (2010). Transcriptional Regulation in Yeast during Diauxic Shift and Stationary Phase. OMICS: A Journal of Integrative Biology, 14(6), 629-638. doi:10.1089/omi.2010.0069Broach, J. R. (2012). Nutritional Control of Growth and Development in Yeast. Genetics, 192(1), 73-105. doi:10.1534/genetics.111.135731Hedbacker, K. (2008). SNF1/AMPK pathways in yeast. Frontiers in Bioscience, 13(13), 2408. doi:10.2741/2854Martínez-Pastor, M., Proft, M., & Pascual-Ahuir, A. (2010). Adaptive Changes of the Yeast Mitochondrial Proteome in Response to Salt Stress. OMICS: A Journal of Integrative Biology, 14(5), 541-552. doi:10.1089/omi.2010.0020Pastor, M. M., Proft, M., & Pascual-Ahuir, A. (2009). Mitochondrial Function Is an Inducible Determinant of Osmotic Stress Adaptation in Yeast. Journal of Biological Chemistry, 284(44), 30307-30317. doi:10.1074/jbc.m109.050682Saito, H., & Posas, F. (2012). Response to Hyperosmotic Stress. Genetics, 192(2), 289-318. doi:10.1534/genetics.112.140863Ruiz-Roig, C., Noriega, N., Duch, A., Posas, F., & de Nadal, E. (2012). The Hog1 SAPK controls the Rtg1/Rtg3 transcriptional complex activity by multiple regulatory mechanisms. Molecular Biology of the Cell, 23(21), 4286-4296. doi:10.1091/mbc.e12-04-0289Bricker, D. K., Taylor, E. B., Schell, J. C., Orsak, T., Boutron, A., Chen, Y.-C., … Rutter, J. (2012). A Mitochondrial Pyruvate Carrier Required for Pyruvate Uptake in Yeast, Drosophila, and Humans. Science, 337(6090), 96-100. doi:10.1126/science.1218099Herzig, S., Raemy, E., Montessuit, S., Veuthey, J.-L., Zamboni, N., Westermann, B., … Martinou, J.-C. (2012). Identification and Functional Expression of the Mitochondrial Pyruvate Carrier. Science, 337(6090), 93-96. doi:10.1126/science.1218530Winzeler, E. A. (1999). Functional Characterization of the S.&nbsp;cerevisiae Genome by Gene Deletion and Parallel Analysis. Science, 285(5429), 901-906. doi:10.1126/science.285.5429.901Ghaemmaghami, S., Huh, W.-K., Bower, K., Howson, R. W., Belle, A., Dephoure, N., … Weissman, J. S. (2003). Global analysis of protein expression in yeast. Nature, 425(6959), 737-741. doi:10.1038/nature02046Alberti, S., Gitler, A. D., & Lindquist, S. (2007). A suite of Gateway®cloning vectors for high-throughput genetic analysis inSaccharomyces cerevisiae. Yeast, 24(10), 913-919. doi:10.1002/yea.1502Westermann, B., & Neupert, W. (2000). Mitochondria-targeted green fluorescent proteins: convenient tools for the study of organelle biogenesis inSaccharomyces cerevisiae. Yeast, 16(15), 1421-1427. doi:10.1002/1097-0061(200011)16:153.0.co;2-uHong, H.-Y., Yoo, G.-S., & Choi, J.-K. (2000). Direct Blue 71 staining of proteins bound to blotting membranes. Electrophoresis, 21(5), 841-845. doi:10.1002/(sici)1522-2683(20000301)21:53.0.co;2-4Nakai, T., Yasuhara, T., Fujiki, Y., & Ohashi, A. (1995). Multiple genes, including a member of the AAA family, are essential for degradation of unassembled subunit 2 of cytochrome c oxidase in yeast mitochondria. Molecular and Cellular Biology, 15(8), 4441-4452. doi:10.1128/mcb.15.8.4441Boubekeur, S., Bunoust, O., Camougrand, N., Castroviejo, M., Rigoulet, M., & Guérin, B. (1999). A Mitochondrial Pyruvate Dehydrogenase Bypass in the YeastSaccharomyces cerevisiae. Journal of Biological Chemistry, 274(30), 21044-21048. doi:10.1074/jbc.274.30.21044Palmieri, L., Lasorsa, F. M., Iacobazzi, V., Runswick, M. J., Palmieri, F., & Walker, J. E. (1999). Identification of the mitochondrial carnitine carrier in Saccharomyces cerevisiae. FEBS Letters, 462(3), 472-476. doi:10.1016/s0014-5793(99)01555-0Martínez-Montañés, F., Pascual-Ahuir, A., & Proft, M. (2010). Toward a Genomic View of the Gene Expression Program Regulated by Osmostress in Yeast. OMICS: A Journal of Integrative Biology, 14(6), 619-627. doi:10.1089/omi.2010.0046Proft, M., Gibbons, F. D., Copeland, M., Roth, F. P., & Struhl, K. (2005). Genomewide Identification of Sko1 Target Promoters Reveals a Regulatory Network That Operates in Response to Osmotic Stress inSaccharomyces cerevisiae. Eukaryotic Cell, 4(8), 1343-1352. doi:10.1128/ec.4.8.1343-1352.2005Divakaruni, A. S., & Murphy, A. N. (2012). A Mitochondrial Mystery, Solved. Science, 337(6090), 41-43. doi:10.1126/science.1225601Smith, R. A. J., Hartley, R. C., Cochemé, H. M., & Murphy, M. P. (2012). Mitochondrial pharmacology. Trends in Pharmacological Sciences, 33(6), 341-352. doi:10.1016/j.tips.2012.03.010Poteet, E., Choudhury, G. R., Winters, A., Li, W., Ryou, M.-G., Liu, R., … Yang, S.-H. (2013). Reversing the Warburg Effect as a Treatment for Glioblastoma. Journal of Biological Chemistry, 288(13), 9153-9164. doi:10.1074/jbc.m112.440354Soga, T. (2013). Cancer metabolism: Key players in metabolic reprogramming. Cancer Science, 104(3), 275-281. doi:10.1111/cas.1208