2017/03/31 12:00

ATRIO 800

SEMINAR

Cytosine-5 RNA Methylation in stem cells, stress and cancer

Sandra Blanco, PhD

Cytosine‐5 methylation (m5C) is one of the best characterised epigenetic modification found in DNA, however the cellular and molecular functions of the same modified nucleobase in RNA remain unclear. I have recently showed the physiological role of m5C in RNA and how alterations of this post-transcriptional modification contribute to human diseases. Mutations in the cytosine-5 RNA methyltransferase NSUN2 cause microcephaly and other neurodevelopment abnormalities in mice and human. Deletion of Nsun2 in mouse also causes tissue stem cell differentiation deficiencies. And in cancer, inhibition of NSUN2 increases tumour-initiating cells self-renewal potential and leads to cancer progression in mice. By analyzing global cytosine-5 RNA methylomes I have found that NSUN2 is a RNA methyltransferase of transfer RNA (tRNA). By comparing tRNA expression data in patient fibroblasts and Nsun2-deficient mice, I found that loss of cytosine-5 methylation increases the endonucleolytic cleavage of tRNAs leading to an accumulation of 5' tRNA-derived small RNA fragments. The functional role of these tRNA-derived small RNAs is to prompt a stress-induced translational programme at the expenses of tissue differentiation. Thus, inhibition or loss of post-transcriptional cytosine-5 methylation locks stem cells and tumour-initiation cells in a distinct undifferentiated state by regulating the translational machinery. Paradoxically, this stress-induced translation inhibition renders tissue stem cells and tumour-initiation cells hypersensitive to cytotoxic stress, as tumour regeneration after treatment with cytotoxic agents is blocked.

2017/05/23 12:00

ATRIO 800

SEMINAR

Mitochondria-Lysosomal Crosstalk in the Immune System

Maria Mittelbrunn, PhD

For many years, mitochondria were viewed as semiautonomous organelles, required only for cellular energetics. This view has been displaced by the concept that mitochondria are fully integrated into the life of the cell and that mitochondrial function and stress response rapidly affect other organelles, and even other tissues.Lack of mitochondrial transcription factor A (Tfam) in T lymphocytes induces a severe decrease in mtDNA content, and a failure to express the key components of the electron transport chain, promoting severe OXPHOS dysfunction. Despite these mitochondrial abnormalities, Tfam-deficient T cells are viable, proliferate and rely on a metabolic program characterized by anaerobic glycolysis. By using this model, we have demonstrated a critical role for mitochondria in the regulation of lysosomal function (Baixauli et al Cell Metabolism 2015) . OXPHOS-deficient cells present abnormal lysosomal function, p62 and sphingomyelin accumulation, and disrupt endolysosomal trafficking pathways and autophagy, thus linking for the first time a primary mitochondrial dysfunction to lysosomal storage disorders (LSDs). Finally, we demonstrate that increasing NAD+ levels mitigate lysosome stress and reduce inflammatory responses in OXPHOS- deficient cells. Our results uncover a mechanism by which mitochondria regulate lysosome function and exacerbated inflammatory responses and identify new strategies to control undesired inflammatory responses. Reference: Baixauli et al. Cell Metab. 2015 Sep 1;22(3):485-98. “Mitochondrial Respiration Controls Lysosomal Function during Inflammatory T Cell Responses”. doi: 10.1016/j.cmet.2015.07.020

2017/06/02 12:00

ATRIO 800

SEMINAR

Studies on the Molecular Recognition of aminoglycoside antibiotics by nucleic acids and proteins

Juan Luis Asensio, PhD

Carbohydrates are involved in a large variety of molecular recognition processes of biological relevance, involving both proteins and nucleic acid receptors. Understanding how these later bio-molecules interact with glycosides represents a fundamental issue in chemical biology with far reaching implications in fundamental biology, biotechnology or drug design. Aminoglycoside antibiotics constitute a paradigmatic example of biologically active glycosides. These compounds, widely used in clinics, bind to a large variety of RNA/DNA fragments, and, consequently, could be considered promising leads for the development of improved nucleic acid ligands. The description, in recent years, of several clinically relevant aminoglycoside/receptor complexes has greatly stimulated the structural-based design of new improved derivatives. Unfortunately, design efforts have frequently met a limited success, reflecting our incomplete understanding of the driving forces that promote complex formation. As a part of an ongoing project oriented to the study of carbohydrate molecular recognition in biological environments we have analyzed several key aspects of the aminoglycoside binding to RNA and proteins, employing a pluridisciplinar approach that includes NMR, molecular modeling, organic synthesis, and different biophysical techniques. The obtained results, together with alternative approaches for the design of improved aminoglycoside ligands, will be discussed. 1.-Jiménez-Moreno, E.; Montalvillo-Jiménez, L.; Santana, A.G.; Gómez, A.M.; Jiménez-Osés, G.; Corzana, F.; Bastida, A.; Jiménez-Barbero, J.; Cañada, F.J.; Gómez-Pinto, I.; González, C.; Asensio, J.L.* J. Am. Chem. Soc. 2016, 138, 20, 6463 2.-Jiménez-Moreno, E.; Jiménez-Osés, G.; Gómez, A.M. Santana, A.G.; Corzana, F.; Bastida, A.; Jiménez-Barbero, J.; Asensio, J.L.* Chemical Science 2015, 6, 6076. 3.-Jiménez-Moreno, E.; Gómez, A.M.; Bastida, A.; Corzana, F.; Jiménez-Oses, G.; Jiménez-Barbero, J.; Asensio, J.L. * Angew. Chem. Int. Edit. 2015, 54, 4344. 4.-Jiménez-Moreno, E.; Gómez-Pinto; I.; Corzana, F.; Santana, A.G.; Revuelta, J.; Bastida, A.; Jiménez-Barbero, J.; González, C.; Asensio, J.L.* Angew. Chem. Int. Edit. 2013, 52, 3148. 5.-Santana, A.G.; Jiménez-Moreno;, E.; Gómez, A.M.; Corzana, F.; González, C.; Jiménez-Oses, G.; Jiménez-Barbero, J.; Asensio, J.L.* J. Am. Chem. Soc. 2013, 135, 3347. 6.-Vacas, T.; Corzana, F.;Jimenez-Oses, G.; González, C.; Gomez, A.M.; Bastida, A.; Revuelta, J.; Asensio, J.L.* J. Am. Chem. Soc. 2010 132, 12074.

2017/06/16 12:00

ATRIO 800

SEMINAR

TBA

Joaquín Castilla, PhD

Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative disorders affecting both humans and animals. TSEs can be of genetic, sporadic or infectious origin. The infectious agent associated with TSEs, termed prion, appears to consist of a single protein, an abnormal conformer (PrPSc) of a natural host protein (PrPC), which propagates by converting host PrPC into a replica of itself. One of the characteristics of prions is their ability to infect some species and not others. This phenomenon is known as transmission barrier. Interestingly, prions occur in the form of different strains that show distinct biological and physicochemical properties, even though they are encoded by PrP with the same amino acid sequence, albeit in presumably different conformations. In general, the transmission barrier is expressed by an incomplete attack rate and long incubation times (time from the animal inoculation until the onset of the clinical signs) which become shorter after serial inoculation passages. Compelling evidence indicates that the transmission barriers are closely related to differences in PrP amino acid sequences between the donor and recipients of infection, as well as the prion strain conformation. Unfortunately, the molecular basis of the transmission barrier phenomenon and its relationship to prion strain conformations is currently unknown and we cannot predict the degree of a species barrier simply by comparing the prion proteins from two species. We have conducted a series of experiments using the Protein Misfolding Cyclic Amplification (PMCA) technique that mimics in vitro some of the fundamental steps involved in prion replication in vivo, albeit with accelerated kinetics. The in vitro generated prions possess key prion features, i.e., they are infectious in vivo and maintain their strain specificity. We have used PMCA to efficiently replicate a variety of prion strains from, among others, mice, hamsters, bank voles, deer, cattle, sheep, and humans. The correlation between in vivo data and our in vitro results suggest that PMCA is a valuable tool for assessing the strength of the transmission barriers between diverse species and for different prion strains; we are using the method to determine which amino acids in the PrPC sequence contribute to the strength of the transmission barrier. These studies are proving very useful in evaluating the potential risks to humans and animals, of not only established prion strains, but also new (atypical) strains. For example, while classical sheep scrapie is unable to cross the human transmission barrier in vitro, bovine spongiform encephalopathy (BSE) propagated in sheep does so efficiently. In addition, we have also generated prions that are infectious to species hitherto considered to be resistant to prion disease.

2017/06/23 12:00

ATRIO 800

SEMINAR

Phospholipase D (PLD) Cell Signaling in Cancer, Inflammation and Heart Ischemia

Prof. Julian G. Cambronero

Phosphatidic acid (PA) is a “master regulator” in the cell, as it sits at the center of all phospholipid metabolism necessary for cellular membranes architecture, as well as being a key signaling molecule with mitogenic properties and a leukocyte chemoattractant (motogen). PA’s concentration in the cell is finely regulated because its involvement in cell functions is very broad. One of the enzymes that regulate the concentration of PA is phospholipase D (PLD) that breaks down phosphatidylcholine from cell membranes and intracellular membranes, into PA and choline. In mammalian cells, the isoforms PLD1 and PLD2 participate in key cell signaling events, including intracellular protein trafficking, cytoskeletal dynamics, cell migration and cell proliferation. We will concentrate on the biology of the mammalian isoform PLD2, describing protein-protein interactions with a wide network of molecules: WASp, Grb2, Ribosomal S6 Kinase, Rac2 and the tyrosine kinases Fes, JAK and EGFR. PLD2 bears also a Guanine Exchange Factor (GEF) activity that is crucial for its role in actin polymerization and cell migration. The regulation of PLD2 by a set of micro-RNAs, as well as the transcription factors Slug/Snail in relation to breast cancer cell invasion and lung metastasis progression will be also discussed. Additionally, the role of PLD1 and PLD2 (and possibly PLD6) isoforms in heart ischemia/reperfusion injury and the aggravating role of leukocytes infiltrating into the injured heart will be presented. PLD is becoming recognized as a major player in the molecular biology of cell migration, as it has roles in two different but important human conditions: cancer metastasis and cardiovascular disease.

2017/07/07 12:00

ATRIO 800

SEMINAR

TBA

Edurne Berra, PhD

Oxygen homeostasis is vital for most organisms and hypoxia, even transient, can provoke irreversible damage. To deal with hypoxia the so-called hypoxia-signalling pathway has evolved. This pathway is essential during embryonic development and in adulthood but it is also associated with a wide range of pathological states, including, but not limited, to ischemic and neurodegenerative diseases, inflammatory and metabolic disorders, and cancer. The research in our group is aimed at deciphering the molecular basis of the hypoxia cascade and its crosstalk with other signalling pathways. We are investigating the role of post-translational modifications (PTMs) by using state-of-the-art in cellulo and in vivo approaches. We have reported the physiological relevance of PHD3-SUMO conjugates as HIF transcriptional repressors. We try to understand the role of DUBs acting as new regulators of the hypoxia cascade that we have identified through a RNAi based genetic screen. In addition, we are interested in understanding the relationship between these signalling networks and pathologies in which hypoxia is involved. Our work has shown the efficient revascularisation triggered by the silencing of PHDs, opening new possibilities for therapy in ischemia. We have also provided new insights into the design of smart systems for cancer therapeutics. We believe that a detailed understanding of the signalling pathway triggered by hypoxia is a major step towards establishing its implications in health and disease and could open future therapeutic applications.