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4.

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5.

Balouz, V., Bracco, L., Ricci, A. D., Romer, G., Aguero, F. and Buscaglia, C. A.

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13.

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14.

Gonzalez, S. N., Mills, J. J., Maugeri, D., Olaya, C., Laguera, B. L., Enders, J. R., Sherman, J., Rodriguez, A., Pierce, J. G., Cazzulo, J. J. and D'Antonio, E. L.

15.

Jager, A. V., Arias, P., Tribulatti, M. V., Brocco, M. A., Pepe, M. V. and Kierbel, A.

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18.

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22.

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30.

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31.

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Short linear motif candidates in the cell entry system used by SARS-CoV-2 and their potential therapeutic implications.

Meszaros, B., Samano-Sanchez, H., Alvarado-Valverde, J., Calyseva, J., Martinez-Perez, E., Alves, R., Shields, D. C., Kumar, M., Rippmann, F., Chemes, L. B. and Gibson, T. J.

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1. Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany. balint.meszaros@embl.de manjeet.kumar@embl.de lchemes@iib.unsam.edu.ar toby.gibson@embl.de.
2. Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
3. Collaboration for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences.
4. Laboratorio de bioinformatica estructural, Fundacion Instituto Leloir, C1405BWE Buenos Aires, Argentina.
5. School of Medicine, University College Dublin, Dublin 4, Ireland.
6. Computational Chemistry & Biology, Merck KGaA, Frankfurter Str. 250, 64293 Darmstadt, Germany.
7. Instituto de Investigaciones Biotecnologicas "Dr. Rodolfo A. Ugalde", IIB-UNSAM, IIBIO-CONICET, Universidad Nacional de San Martin, CP1650 San Martin, Buenos Aires, Argentina.
   balint.meszaros@embl.de manjeet.kumar@embl.de lchemes@iib.unsam.edu.ar toby.gibson@embl.de.
   

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SARS-CoV-2: From entry to autophagy?

SARS-CoV-2, the virus that causes COVID-19, enters cells through endocytosis upon binding to the cell surface receptor ACE2 and potentially others, including integrins. Using bioinformatics, Mészáros et al. predicted the presence of short amino acid sequences, called short linear motifs (SLiMs), in the cytoplasmic tails of ACE2 and various integrins that may engage the endocytic and autophagic machinery. Using affinity binding assays, Kliche et al. not only confirmed that many of these predicted SLiMs interacted with target peptides in various components of the endocytosis and autophagy machinery but also found that these interactions were regulated by the phosphorylation of SLiM-adjacent amino acids. Together, these findings have identified a potential link between autophagy and integrin signaling and could lead to new ways to prevent viral infection.

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The first reported receptor for SARS-CoV-2 on host cells was the angiotensin-converting enzyme 2 (ACE2). However, the viral spike protein also has an RGD motif, suggesting that cell surface integrins may be co-receptors. We examined the sequences of ACE2 and integrins with the Eukaryotic Linear Motif (ELM) resource and identified candidate short linear motifs (SLiMs) in their short, unstructured, cytosolic tails with potential roles in endocytosis, membrane dynamics, autophagy, cytoskeleton, and cell signaling. These SLiM candidates are highly conserved in vertebrates and may interact with the μ2 subunit of the endocytosis-associated AP2 adaptor complex, as well as with various protein domains (namely, I-BAR, LC3, PDZ, PTB, and SH2) found in human signaling and regulatory proteins. Several motifs overlap in the tail sequences, suggesting that they may act as molecular switches, such as in response to tyrosine phosphorylation status. Candidate LC3-interacting region (LIR) motifs are present in the tails of integrin β3 and ACE2, suggesting that these proteins could directly recruit autophagy components. Our findings identify several molecular links and testable hypotheses that could uncover mechanisms of SARS-CoV-2 attachment, entry, and replication against which it may be possible to develop host-directed therapies that dampen viral infection and disease progression. Several of these SLiMs have now been validated to mediate the predicted peptide interactions.

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Science Signaling. 14(665): (2021)

A genomic island in Brucella involved in the adhesion to host cells: Identification of a new adhesin and a translocation factor.

Lopez, P., Guaimas, F., Czibener, C. and Ugalde, J. E.

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1. Instituto de Investigaciones Biotecnologicas 'Dr. Rodolfo A. Ugalde', IIB-UNSAM, IIBIO-CONICET, Universidad Nacional de San Martin, Buenos Aires, Argentina.

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Adhesion to host cells is the first step in the virulence cycle of any pathogen. In Gram-negative bacteria, adhesion is mediated, among other virulence factors such as the lipopolysaccharides, by specific outer-membrane proteins generally termed adhesins that belong to a wide variety of families and have different evolutionary origins. In Brucella, a widespread zoonotic pathogen of animal and human health concern, adhesion is central as it may determine the intracellular fate of the bacterium, an essential stage in its pathogenesis. In the present paper, we further characterised a genomic locus that we have previously reported encodes an adhesin (BigA) with a bacterial immunoglobulin-like domain (BIg-like). We found that this region encodes a second adhesin, which we have named BigB; and PalA, a periplasmic protein necessary for the proper display in the outer membrane of BigA and BigB. Deletion of bigB or palA diminishes the adhesion of the bacterium and overexpression of BigB dramatically increases it. Incubation of cells with the recombinant BIg-like domain of BigB induced important cytoskeletal rearrangements and affected the focal adhesion sites indicating that the adhesin targets cell-cell or cell-matrix proteins. We additionally show that PalA has a periplasmic localisation and is completely necessary for the proper display of BigA and BigB, probably avoiding their aggregation and facilitating their transport to the outer membrane. Our results indicate that this genomic island is entirely devoted to the adhesion of Brucella to host cells..

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Cell Microbiol 22(11): e13245 (2020)

Transmigration of Trypanosoma cruzi Trypomastigotes through 3D Spheroids Mimicking Host Tissues.

Rodriguez, M. E., Rizzi, M., Caeiro, L., Masip, Y., Sanchez, D. O. and Tekiel, V.

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1. Instituto de Investigaciones Biotecnologicas "Dr R. Ugalde", IIBIO, Universidad Nacional de San Martin (UNSAM) - CONICET, Pcia de Buenos Aires, Argentina. Instituto de Investigaciones Biotecnologicas "Dr R. Ugalde", IIBIO, Universidad Nacional de San Martin (UNSAM) - CONICET, Pcia de Buenos Aires, Argentina.
   Corresponding author: E-mail: valet@iib.unsam.edu.ar.

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While cellular invasion by T. cruzi trypomastigotes and intracellular amastigote replication are well-characterized events that have been described by using 2D monolayer cultures, other relevant parasite-host interactions, like the dynamics of tissue invasiveness, cannot be captured using monolayer cultures. Spheroids constitute a valuable three-dimensional (3D) culture system because they mimic the microarchitecture of tissues and provide an environment similar to the encountered in natural infections, which includes the presence of extracellular matrix as well as 3D cell-cell interactions. In this work, we describe a protocol for studying transmigration of T. cruzi trypomastigotes into 3D spheroids. In the experimental setup, cells and parasites are labelled with two fluorescent dyes, allowing their visualization by confocal microscopy. We also describe the general procedure and setting of the confocal microscope and downstream applications for acquisition and reconstruction of 3D images. This model was employed to analyze the transmigration of trypomastigotes from the highly virulent and pantropic RA T. cruzi strain. Of course, other aspects encountered by T. cruzi in the mammalian host environment can be studied with this methodology.

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Methods in Molecular Biology 1955: 165-177 (2019)

Chagas Disease Diagnostic Applications: Present Knowledge and Future Steps.

Balouz, V., Agüero, F. and Buscaglia, C.A.

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1. Instituto de Investigaciones Biotecnologicas e Instituto Tecnologico de Chascomus (IIB-INTECH), Universidad Nacional de San Martín (UNSAM) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
   Corresponding author: E-mail: cbuscaglia89@gmail.com

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This chapter was originally published in the book Advances in Parasitology, Volume 97. The copy attached is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research, and educational use. This includes without limitation use in instruction at your institution, distribution to specific colleagues, and providing a copy to your institution's administrator.

From Balouz, V., Agüero, F., Buscaglia, C.A., 2017.

Chagas Disease Diagnostic Applications: Present Knowledge and Future Steps. In: Rollinson, D., Stothard, J.R. (Eds.), Advances in Parasitology, pp. 1–45.

ISBN: 9780128115589

Copyright © 2017 Elsevier Ltd. All rights reserved Academic Press

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Advances in Parasitology, Volume 97 , Chapter 1 pages 1-45 (2017)

The Trypanosoma cruzi surface, a nanoscale patchwork quilt.

Mucci, J., Lantos, A.B., Buscaglia, C.A., Leguizamón, M.S. and Campetella, O.

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1. Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico de Chascomús (IIB-INTECH), Universidad Nacional de San Martín (UNSAM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), B1650HMP San Martín, Buenos Aires, Argentina.
2. Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico de Chascomús (IIB-INTECH), Universidad Nacional de San Martín (UNSAM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), B1650HMP San Martín, Buenos Aires, Argentina. Electronic address: oscar@unsam.edu.ar.

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Abstract

The Trypanosoma cruzi trypomastigote membrane provides a major protective role against mammalian host-derived defense mechanisms while allowing the parasite to interact with different cell types and trigger pathogenesis. This surface has been historically appreciated as a rather unstructured 'coat', mainly consisting of a continuous layer of glycolipids and heavily O-glycosylated mucins, occasionally intercalated with different developmentally regulated molecules displaying adhesive and/or enzymatic properties. Recent findings, however, indicate that the trypomastigote membrane is made up of multiple, densely packed and discrete 10-150nm lipid-driven domains bearing different protein composition; hence resembling a highly organized 'patchwork quilt' design. Here, we discuss different aspects underlying the biogenesis, assembly, and dynamics of this cutting-edge fashion outfit, as well as its functional implications.

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Volume 33 , Issue 2 , 102 - 112 (2017)

Albumin–Folate Conjugates for Drug-targeting in Photodynamic Therapy.

Butzbach K, Rasse-Suriani FA, Gonzalez MM, Cabrerizo FM, Epe B.

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1. Institute of Pharmacy and Biochemistry, University of Mainz, Mainz, Germany.
2. Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico de Chascomús (IIB-INTECH), Universidad Nacional de San Martín (UNSAM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Chascomús, Argentina.

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Abstract

Photodynamic therapy (PDT) is based on the cytotoxicity of photosensitizers in the presence of light. Increased selectivity and effectivity of the treatment is expected if a specific uptake of the photosensitizers into the target cells, often tumor cells, can be achieved. An attractive transporter for that purpose is the folic acid receptor α (FRα), which is overexpressed on the surface of many tumor cells and mediates an endocytotic uptake. Here, we describe the synthesis and photobiological characterization of polar β-carboline derivatives as photosensitizers covalently linked to folate-tagged albumin as the carrier system. The particles were taken up by KB (human carcinoma) cells within <90 min and then co-localized with a lysosomal marker. FRα antibodies prevented the uptake and also the corresponding conjugate without folate was not taken up. Accordingly, a folate-albumin-β-carbolinium conjugate proved to be phototoxic, while the corresponding albumin–β-carbolinium conjugates without FA were nontoxic, both with and without irradiation. An excess of free folate as competitor for the FRα-mediated uptake completely inhibited the photocytotoxicity. Interestingly, the albumin conjugates are devoid of photodynamic activity under cell-free conditions, as shown for DNA as a target. Thus, phototoxicity requires cellular uptake and lysosomal degradation of the conjugates. In conclusion, albumin–folate conjugates appear to be promising vehicles for a tumor cell targeted PDT

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Photochem Photobiol. Volume 92, Issue 4, pp 611-619 (2016)

Towards high-throughput immunomics for infectious diseases: use of next-generation peptide microarrays for rapid discovery and mapping of antigenic determinants.

Carmona SJ, Nielsen M, Schäfer-Nielsen C, Altcheh J, Mucci JS, Balouz V, Tekiel V, Frasch AC, Campetella O, Buscaglia CA, Agüero F.

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1. From the ‡Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico de Chascomús, Universidad de San Martín - CONICET, Sede San Martín, B 1650 HMP, San Martín, Buenos Aires, Argentina
2. From the ‡Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico de Chascomús, Universidad de San Martín - CONICET, Sede San Martín, B 1650 HMP, San Martín, Buenos Aires, Argentina; §Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, 2800 Lyngby, Denmark
3. Schafer-N ApS, 2100 Copenhagen, Denmark
4. Servicio de Parasitología y Chagas, Hospital de Niños Ricardo Gutiérrez, Ciudad de Buenos Aires, Argentina.
5. From the ‡Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico de Chascomús, Universidad de San Martín - CONICET, Sede San Martín, B 1650 HMP, San Martín, Buenos Aires, Argentina; fernan@unsam.edu.ar.

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Abstract

Complete characterization of antibody specificities associated to natural infections is expected to provide a rich source of serologic biomarkers with potential applications in molecular diagnosis, follow-up of chemotherapeutic treatments, and prioritization of targets for vaccine development. Here, we developed a highly-multiplexed platform based on next-generation high-density peptide microarrays to map these specificities in Chagas Disease, an exemplar of a human infectious disease caused by the protozoan Trypanosoma cruzi. We designed a high-density peptide microarray containing more than 175,000 overlapping 15mer peptides derived from T. cruzi proteins. Peptides were synthesized in situ on microarray slides, spanning the complete length of 457 parasite proteins with fully overlapped 15mers (1 residue shift). Screening of these slides with antibodies purified from infected patients and healthy donors demonstrated both a high technical reproducibility as well as epitope mapping consistency when compared with earlier low-throughput technologies. Using a conservative signal threshold to classify positive (reactive) peptides we identified 2,031 disease-specific peptides and 97 novel parasite antigens, effectively doubling the number of known antigens and providing a 10-fold increase in the number of fine mapped antigenic determinants for this disease. Finally, further analysis of the chip data showed that optimizing the amount of sequence overlap of displayed peptides can increase the protein space covered in a single chip by at least ∼threefold without sacrificing sensitivity. In conclusion, we show the power of high-density peptide chips for the discovery of pathogen-specific linear B-cell epitopes from clinical samples, thus setting the stage for high-throughput biomarker discovery screenings and proteome-wide studies of immune responses against pathogens.

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Mol Cell Proteomics. Volume 14, Issue 1, pp 1871-1884 (2015)

Shallow lakes from the Central Plains of Argentina: an overview and worldwide comparative analysis of their basic limnological features.

Nadia Diovisalvi, Vanesa Y. Bohn, María Cintia Piccolo, Gerardo M. E. Perillo, Claudio Baigún, Horacio E. Zagarese

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1. Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (CONICET-UNSAM), Chascomús, Buenos Aires, Argentina
2. Departamento de Geografía y Turismo, Universidad Nacional del Sur (UNS), Bahía Blanca, Buenos Aires, Argentina
3. Departamento de Geología, Universidad Nacional del Sur (UNS), Bahía Blanca, Buenos Aires, Argentina
4. Instituto Argentino de Oceanografía (IADO–CONICET), Bahía Blanca, Buenos Aires, Argentina

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Abstract

The Central Plains of Argentina is a heterogeneous environment, but the lakes there share some fundamental features: they are all shallow and polymictic as being well exposed to wind. First, we provide a synthesis of the climate, geology, and hydrological network. We also discussed shallow lakes origin and their limnological and biological salient features. Second, we focus on Pampean shallow lakes from a global perspective, comparing the limnological variables: total phosphorus concentration (TP), total nitrogen concentration (TN), chlorophyll a (Chl a) concentrations, and Secchi disk reading (SD) from a compiled database. No significant differences in the Chl a vs. TP relationship were found between Pampean and other shallow lakes. Otherwise, the chlorophyll yield per unit of phosphorus of Pampean lakes is similar to the world shallow lakes average. Moreover, the relationship SD vs. Chl a differed significantly between Pampean and the remaining world lakes, about 50–60%. When confronted against other lakes worldwide, Pampean shallow lakes depart from most of them as having higher TP, TN, and Chl a concentrations and much lower SD transparency, and therefore they stand as extremes of the trophic-state continuum. Despite their highly turbid state, these lakes provide valuable ecosystem services that are highly appreciated and mobilize important economic resources.

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Hydrobiologia. June 2015, Volume 752, Issue 1, pp 5-20

Plant interactions with other organisms: molecules, ecology and evolution.

Amy T. Austin and Carlos L. Ballaré

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1. IFEVA, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad de Buenos Aires, C1417DSE, Buenos Aires, Argentina.

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Abstract

The plant sciences, during much of the 20th century, evolved as a group of disciplines that sought to explain plant responses to factors of the abiotic environment, such as water, mineral nutrients and light. In the last two decades, there have been major advances in our understanding of how plants interact with a growing list of other components of their biotic environment, including other plants, animal consumers and detritivores, pollinators, and beneficial and pathogenic microorganisms. This progress has rendered a much richer picture of plant function in real life than the one produced by traditional models of physiological responses to simple variations in abiotic factors. Simultaneously, this progress has revealed major gaps in our understanding of the evolution of plant adaptation, the molecular mechanisms that mediate phenotypic plasticity in complex biotic scenarios, and the ecosystem consequences of these interactions.

The overarching goal of the 32nd New Phytologist Symposium (NPS), 'Plant interactions with other organisms: molecules, ecology and evolution', was to bring together researchers working on various aspects of plant interactions with the biotic world. Despite the fact that exciting advances have been made in individual subfields, which captured the attention of specialists in each particular discipline, there has been little communication across disciplinary and scale boundaries for synthesizing our conceptual understanding of how plants interact with components of the biotic environment. This Special Issue features articles from the invited speakers of the 32nd NPS, and represents a collection that describes progress in a broad cross-section of disciplines. All articles are written keeping in mind the multidisciplinary nature of the audience. This combination of research papers, review papers and commentaries aims to provide a multifaceted view of the field of plant biotic interactions, which we hope will be appealing not only to the specialist but also to anyone interested in plant biology and ecology.

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New Phytologist. Volume 204, Issue 2, pages 257–260, October 2014

Linking phytochrome to plant immunity: low red : far-red ratios increase Arabidopsis susceptibility to Botrytis cinerea by reducing the biosynthesis of indolic glucosinolates and camalexin.

Cargnel MD, Demkura PV, Ballaré CL.

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1. IFEVA, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad de Buenos Aires, C1417DSE, Buenos Aires, Argentina.

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Abstract

Shade-intolerant plants respond to low red : far-red (R : FR) ratios, which signal the proximity of potential competitors, by down-regulating immune responses. Here we investigated the mechanisms underlying this immune suppression in Arabidopsis. We used genetic, transcriptomic and metabolomic approaches to examine the functional connections between R : FR ratio and Arabidopsis resistance to the fungus Botrytis cinerea. Low R : FR ratios reduced the concentration of indol-3-ylmethyl glucosinolate (I3M) (an indolic glucosinolate, iGS) and camalexin in plants inoculated with B. cinerea, and attenuated the I3M response triggered by jasmonate elicitation. These effects on metabolite abundance correlated with reduced expression of iGS and camalexin biosynthetic genes. Furthermore, the effect of low R : FR increasing Arabidopsis susceptibility to B. cinerea was not present in mutants deficient in the biosynthesis of camalexin (pad3) or metabolism of iGS (pen2). Finally, in a mutant deficient in the JASMONATE ZIM DOMAIN-10 (JAZ10) protein, which does not respond to low R : FR with increased susceptibility to B. cinerea, supplemental FR failed to down-regulate iGS production. These results indicate that suppression of Arabidopsis immunity against B. cinerea by low R : FR ratios is mediated by reduced levels of Trp-derived defenses, and provide further evidence for a functional role of JAZ10 in the link between phytochrome and jasmonate signaling.

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New Phytologist. Volume 204, Issue 2, pages 42-54, October 2014.

Identification of a type IV secretion substrate of Brucella abortus that participates in the early stages of intracellular survival.

Döhmer PH, Valguarnera E, Czibener C, Ugalde JE.

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1. Instituto de Investigaciones Biotecnológicas 'Dr. Rodolfo A. Ugalde', Instituto Tecnológico de Chascomús, IIB-INTECH, CONICET, Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina.

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Abstract

Brucella abortus, the aetiological agent of bovine brucellosis, is an intracellular pathogen whose virulence is completely dependent on a type IV secretion system. This secretion system translocates effector proteins into the host cell to modulate the intracellular fate of the bacterium in order to establish a secure niche were it actively replicates. Although much has been done in understanding how this secretion system participates in the virulence process, few effector proteins have been identified to date. We describe here the identification of a type IV secretion substrate (SepA) that is only present in Brucella spp. and has no detectable homology to known proteins. This protein is secreted in a virB-dependent manner in a two-step process involving a periplasmic intermediate and secretion is necessary for its function. The deletion mutant showed a defect in the early stages of intracellular replication in professional and non-professional phagocytes although it invades the cells more efficiently than the wild-type parental strain. Our results indicate that, even though the mutant was more invasive, it had a defect in excluding the lysosomal marker Lamp-1 and was inactivated more efficiently during the early phases of the intracellular life cycle.

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Cellular Microbiology Volume 6, Issue 3, pp 396-410 (2014)

No time for candy: passionfruit (Passiflora edulis) plants down-regulate damage-induced extra floral nectar production in response to light signals of competition

Miriam M. Izaguirre, Carlos A. Mazza, María S. Astigueta, Ana M. Ciarla, Carlos L. Ballaré

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1. Facultad de Agronomía, Universidad de Buenos Aires, Ave. San Martín 4453, C1417DSE, Buenos Aires, Argentina.
2. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA), Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Ave. San Martín 4453, C1417DSE, Buenos Aires, Argentina.
3. Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina.

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Abstract

Plant fitness is often defined by the combined effects of herbivory and competition, and plants must strike a delicate balance between their ability to capture limiting resources and defend against herbivore attack. Many plants use indirect defenses, such as volatile compounds and extrafloral nectaries (EFN), to attract canopy arthropods that are natural enemies of herbivorous organisms. While recent evidence suggests that upon perception of low red to far-red (R:FR) ratios, which signal the proximity of competitors, plants down-regulate resource allocation to direct chemical defenses, it is unknown if a similar phytochrome-mediated response occurs for indirect defenses. We evaluated the interactive effects of R:FR ratio and simulated herbivory on nectar production by EFNs of passionfruit (Passiflora edulis f. flavicarpa). The activity of petiolar EFNs dramatically increased in response to simulated herbivory and hormonal treatment with methyl jasmonate (MeJA). Low R:FR ratios, which induced a classic "shade-avoidance" repertoire of increased stem elongation in P. edulis, strongly suppressed the EFN response triggered by simulated herbivory or MeJA application. Strikingly, the EFN response to wounding and light quality was localized to the branches that received the treatments. In vines like P. edulis, a local response would allow the plants to precisely adjust their light harvesting and defense phenotypes to the local conditions encountered by individual branches when foraging for resources in patchy canopies. Consistent with the emerging paradigm that phytochrome regulation of jasmonate signaling is a central modulator of adaptive phenotypic plasticity, our results demonstrate that light quality is a strong regulator of indirect defenses.

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Oecologia - September 2013, Volume 173, Issue 1, pp 213-221

DNA methyltransferase3A as a molecular switch mediating the neural tube-to-neural crest fate transition.

Hu, N.; Strobl-Mazzulla, P.H.; Sauka-Spengler, T.; Bronner, M.

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Division of Biology, California Institute of Technology, Pasadena, California 91125, USA;

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Abstract

Here, we explore whether silencing via promoter DNA methylation plays a role in neural versus neural crest cell lineage decisions. We show that DNA methyltransferase3A (DNMT3A) promotes neural crest specification by directly mediating repression of neural genes like Sox2 and Sox3. DNMT3A is expressed in the neural plate border, and its knockdown causes ectopic Sox2 and Sox3 expression at the expense of neural crest markers. In vivo chromatin immunoprecipitation of neural folds demonstrates that DNMT3A specifically associates with CpG islands in the Sox2 and Sox3 promoter regions, resulting in their repression by methylation. Thus, DNMT3A functions as a molecular switch, repressing neural to favor neural crest cell fate.

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Genes & Development 26(21):2380-2385 (2012).

Fast motility of the malaria transmission stage is essential for intra-dermal migration and triggered by the small heat-shock protein sHSP20.

Montagna G, Buscaglia CA, Münter S, Brinkmann V, Frischknecht F, Matuschewski K.

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Instituto de Investigaciones Biotecnológicas (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Argentina.

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Abstract

Plasmodium sporozoites, single cell eukaryotic pathogens, use their own actin/myosin-based motor machinery for life cycle progression, which includes forward locomotion, penetration of cellular barriers, and invasion of target cells. To display fast gliding motility, the parasite uses a high turnover of actin polymerization and adhesion sites. Paradoxically, only a few classic actin regulatory proteins appear to be encoded in the Plasmodium genome. Small heat shock proteins have been associated with cytoskeleton modulation in various biological processes. In this study, we identify HSP20 as a novel player in Plasmodium motility and provide molecular genetics evidence for a critical role of a small heat shock protein in cell traction and motility. We demonstrate that HSP20 ablation profoundly affects sporozoite-substrate adhesion, which translates into aberrant speed and directionality in vitro. Loss of HSP20 function impairs migration in the host, an important sporozoite trait required to find a blood vessel and reach the liver after being deposited in the skin by the mosquito. Our study also shows that fast locomotion of sporozoites is crucial during natural malaria transmission

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J Biol Chem. 287, 2410-2422 (2012).

Toxoplasma gondii: without stress there is no life.

Figueras MJ, Angel SO, Cóceres VM and Alomar ML.

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Instituto de Investigaciones Biotecnológicas (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Argentina.

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Abstract

Toxoplasma gondii is an important pathogen of human and domestic animals. It has a complex life cycle which includes the transition from one host to another, being only exposed to the environment during one stage, as highly resistant oocysts. Interestingly, in the intermediate host (non-feline mammalians and birds) the parasite presents an asexual cycle with two stages that can interconvert without its passage in the definite host (felines). The asexual cycle is very important in the establishment of the infection and on its pathogenesis and it could be driven by different kind of stressors. Therefore, the response to environmental and host stresses is essential to their viability and successful progression through their life cycle. The heat shock proteins are key molecules not only in the resistance to different stressors, but they are also involved in the optimal differentiation as well as in other biological processes in T. gondii. This chapter summarizes the findings on different aspects of T. gondii stress responses and the implication of these processes in the biology and pathogenesis of this parasite.

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Stress Response in Microbiology Ed. Jose M. Requena. Caister Academic Press, Chapter 13, 303-319, 2012.

Neuronal glycoprotein M6a induces filopodia formation via association with cholesterol-rich lipid rafts.

Scorticati C, Formoso K, Frasch AC.

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Instituto de Investigaciones Biotecnológicas (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Argentina.

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Abstract

A neuronal integral membrane glycoprotein M6a has been suggested to be involved in a number of biological processes, including neuronal remodeling and differentiation, trafficking of mu-opioid receptors, and Ca(2+) transportation. Moreover, pathological situations such as chronic stress in animals and depression in humans have been associated with alterations in M6a sequence and expression. The mechanism of action of M6a is essentially unknown. In this work, we analyze the relevance of M6a distribution in plasma membrane, namely its lipid microdomain targeting, for its biological function in filopodia formation. We demonstrate that M6a is localized in membrane microdomains compatible with lipid rafts in cultured rat hippocampal neurons. Removal of cholesterol from neuronal membranes with methyl-ß-cyclodextrin decreases M6a-induced filopodia formation, an effect that is reversed by the addition of cholesterol. Inhibition of Src kinases and MAPK prevents filopodia formation in M6a-over-expressing neurons. Src-deficient SYF cells over-expressing M6a fail to promote filopodia formation. Taken together, our findings reveal that the association of M6a with lipid rafts is important for its role in filopodia formation and Src and MAPK kinases participate in M6a signal propagation.

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J Neurochem. 2011 Mar 23. doi: 10.1111/j.1471-4159.2011.07252.x. [Epub ahead of print]

Dendritic arbors of developing retinal ganglion cells are stabilized by beta 1-integrins.

Marrs GS, Honda T, Fuller L, Thangavel R, Balsamo J, Lilien J, Dailey ME and Arregui C.

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Department of Biological Sciences, The University of Iowa, Iowa City, IA 52242, USA.
Program in Neuroscience, The University of Iowa, Iowa City, IA 52242, USA.
Instituto de Investigaciones Biotecnologicas, IIB-INTECH, Universidad de San Martin, 1650, San Martin, Buenos Aires, Argentina

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Abstract

The architecture of dendritic arbors is a defining characteristic of neurons and is established through a sequential but overlapping series of events involving process outgrowth and branching, stabilization of the global pattern, and synapse formation. To investigate the roles of cadherins and beta1-integrins in maintaining the global architecture of the arbor, we used membrane permeable peptides and transfection with dominant-negative constructs to disrupt adhesion molecule function in intact chick neural retina at a stage when the architecture of the ganglion cell (RGC) arbor is established but synapse formation is just beginning. Inactivation of beta1-integrins induces rapid dendrite retraction, with loss of dynamic terminal filopodia followed by resorption of major branches. Disruption of N-cadherin-beta-catenin interactions has no effect; however, dendrites do retract following perturbation of the juxtamembrane region of N-cadherin, which disrupts N-cadherin-mediated adhesion and initiates a beta1-integrin inactivating signal. Thus, developing RGC dendritic arbors are stabilized by beta1-integrin-dependent processes.

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Molecular and Cellular NeuroscienceVolume 32, Issue 3 , July 2006, Pages 230-241

The genome sequence of Trypanosoma cruzi, etiologic agent of Chagas disease.

El-Sayed NM, Myler PJ, Bartholomeu DC, Nilsson D, Aggarwal G, Tran AN, Ghedin E, Worthey EA, Delcher AL, Blandin G, Westenberger SJ, Caler E, Cerqueira GC, Branche C, Haas B, Anupama A, Arner E, Aslund L, Attipoe P, Bontempi E, Bringaud F, Burton P, Cadag E, Campbell DA, Carrington M, Crabtree J, Darban H, da Silveira JF, de Jong P, Edwards K, Englund PT, Fazelina G, Feldblyum T, Ferella M, Frasch AC, Gull K, Horn D, Hou L, Huang Y, Kindlund E, Klingbeil M, Kluge S, Koo H, Lacerda D, Levin MJ, Lorenzi H, Louie T, Machado CR, McCulloch R, McKenna A, Mizuno Y, Mottram JC, Nelson S, Ochaya S, Osoegawa K, Pai G, Parsons M, Pentony M, Pettersson U, Pop M, Ramirez JL, Rinta J, Robertson L, Salzberg SL, Sanchez DO, Seyler A, Sharma R, Shetty J, Simpson AJ, Sisk E, Tammi MT, Tarleton R, Teixeira S, Van Aken S, Vogt C, Ward PN, Wickstead B, Wortman J, White O, Fraser CM, Stuart KD, Andersson B.

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Department of Parasite Genomics, Institute for Genomic Research, Rockville, MD 20850, USA. nelsayed@tigr.org

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Abstract

Whole-genome sequencing of the protozoan pathogen Trypanosoma cruzi revealed that the diploid genome contains a predicted 22,570 proteins encoded by genes, of which 12,570 represent allelic pairs. Over 50% of the genome consists of repeated sequences, such as retrotransposons and genes for large families of surface molecules, which include trans-sialidases, mucins, gp63s, and a large novel family (>1300 copies) of mucin-associated surface protein (MASP) genes. Analyses of the T. cruzi, T. brucei, and Leishmania major (Tritryp) genomes imply differences from other eukaryotes in DNA repair and initiation of replication and reflect their unusual mitochondrial DNA. Although the Tritryp lack several classes of signaling molecules, their kinomes contain a large and diverse set of protein kinases and phosphatases; their size and diversity imply previously unknown interactions and regulatory processes, which may be targets for intervention.

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Science 2005 Jul 15;309(5733):409-15.

The genome of the kinetoplastid parasite, Leishmania major.

Ivens AC, Peacock CS, Worthey EA, Murphy L, Aggarwal G, Berriman M, Sisk E, Rajandream MA, Adlem E, Aert R, Anupama A, Apostolou Z, Attipoe P, Bason N, Bauser C, Beck A, Beverley SM, Bianchettin G, Borzym K, Bothe G, Bruschi CV, Collins M, Cadag E, Ciarloni L, Clayton C, Coulson RM, Cronin A, Cruz AK, Davies RM, De Gaudenzi J, Dobson DE, Duesterhoeft A, Fazelina G, Fosker N, Frasch AC, Fraser A, Fuchs M, Gabel C, Goble A, Goffeau A, Harris D, Hertz-Fowler C, Hilbert H, Horn D, Huang Y, Klages S, Knights A, Kube M, Larke N, Litvin L, Lord A, Louie T, Marra M, Masuy D, Matthews K, Michaeli S, Mottram JC, Müller-Auer S, Munden H, Nelson S, Norbertczak H, Oliver K, O'neil S, Pentony M, Pohl TM, Price C, Purnelle B, Quail MA, Rabbinowitsch E, Reinhardt R, Rieger M, Rinta J, Robben J, Robertson L, Ruiz JC, Rutter S, Saunders D, Schäfer M, Schein J, Schwartz DC, Seeger K, Seyler A, Sharp S, Shin H, Sivam D, Squares R, Squares S, Tosato V, Vogt C, Volckaert G, Wambutt R, Warren T, Wedler H, Woodward J, Zhou S, Zimmermann W, Smith DF, Blackwell JM, Stuart KD, Barrell B, Myler PJ.

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Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire CB10 1SA, UK. alicat@sanger.ac.uk

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Abstract

Leishmania species cause a spectrum of human diseases in tropical and subtropical regions of the world. We have sequenced the 36 chromosomes of the 32.8-megabase haploid genome of Leishmania major (Friedlin strain) and predict 911 RNA genes, 39 pseudogenes, and 8272 protein-coding genes, of which 36% can be ascribed a putative function. These include genes involved in host-pathogen interactions, such as proteolytic enzymes, and extensive machinery for synthesis of complex surface glycoconjugates. The organization of protein-coding genes into long, strand-specific, polycistronic clusters and lack of general transcription factors in the L. major, Trypanosoma brucei, and Trypanosoma cruzi (Tritryp) genomes suggest that the mechanisms regulating RNA polymerase II-directed transcription are distinct from those operating in other eukaryotes, although the trypanosomatids appear capable of chromatin remodeling. Abundant RNA-binding proteins are encoded in the Tritryp genomes, consistent with active posttranscriptional regulation of gene expression

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Science 2005 Jul 15;309(5733):436-42.