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  1. Article ; Online: An AMP-activated protein kinase complex with two distinctive alpha subunits is involved in nutritional stress responses in Trypanosoma cruzi.

    Tamara Sternlieb / Alejandra C Schoijet / Patricio D Genta / Salomé C Vilchez Larrea / Guillermo D Alonso

    PLoS Neglected Tropical Diseases, Vol 15, Iss 5, p e

    2021  Volume 0009435

    Abstract: Trypanosoma cruzi, the etiological agent of Chagas disease, has a digenetic life cycle. In its passage from the insect vector to the mammalian host, and vice versa, it must be prepared to cope with abrupt changes in environmental conditions, such as ... ...

    Abstract Trypanosoma cruzi, the etiological agent of Chagas disease, has a digenetic life cycle. In its passage from the insect vector to the mammalian host, and vice versa, it must be prepared to cope with abrupt changes in environmental conditions, such as carbon source, pH, temperature and osmolarity, in order to survive. Sensing and signaling pathways that allow the parasite to adapt, have unique characteristics with respect to their hosts and other free-living organisms. Many of the canonical proteins involved in these transduction pathways have not yet been found in the genomes of these parasites because they present divergences either at the functional, structural and/or protein sequence level. All of this makes these pathways promising targets for therapeutic drugs. The AMP-activated protein kinase (AMPK) is a serine/threonine kinase activated by environmental stresses such as osmotic stress, hypoxia, ischaemia and exercise that results in reduction of ATP and increase of AMP levels. Thus, AMPK is regarded as a fuel gauge, functioning both as a nutrient and an energy sensor, to maintain energy homeostasis and, eventually, to protect cells from death by nutrient starvation. In the present study we report the characterization of AMPK complexes for the first time in T. cruzi and propose the function of TcAMPK as a novel regulator of nutritional stress in epimastigote forms. We show that there is phosphotransferase activity specific for SAMS peptide in epimastigotes extracts, which is inhibited by Compound C and is modulated by carbon source availability. In addition, TcAMPKα2 subunit has an unprecedented functional substitution (Ser x Thr) at the activation loop and its overexpression in epimastigotes led to higher autophagic activity during prolonged nutritional stress. Moreover, the over-expression of the catalytic subunits resulted in antagonistic phenotypes associated with proliferation. Together, these results point to a role of TcAMPK in autophagy and nutrient sensing, key processes for the survival of ...
    Keywords Arctic medicine. Tropical medicine ; RC955-962 ; Public aspects of medicine ; RA1-1270
    Subject code 572
    Language English
    Publishing date 2021-05-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article: The Phosphatidylinositol 3‐kinase Class III Complex Containing TcVps15 and TcVps34 Participates in Autophagy in Trypanosoma cruzi

    Schoijet, Alejandra C / Tamara Sternlieb / Guillermo D. Alonso

    journal of eukaryotic microbiology. 2017 May, v. 64, no. 3

    2017  

    Abstract: Autophagy is a degradative process by which eukaryotic cells digest their own components to provide aminoacids that may function as energy source under nutritional stress conditions. There is experimental evidence for autophagy in parasitic protists ... ...

    Abstract Autophagy is a degradative process by which eukaryotic cells digest their own components to provide aminoacids that may function as energy source under nutritional stress conditions. There is experimental evidence for autophagy in parasitic protists belonging to the family Trypanosomatidae. However, few proteins implicated in this process have been characterized so far in these parasites. Moreover, it has been shown that autophagy is involved in Trypanosoma cruzi differentiation and thus might have a role in pathogenicity. Here, we report the cloning and biochemical characterization of TcVps15. In addition, we demonstrate that TcVps15 interact with the PI3K TcVps34 and that both proteins associate with cellular membranes. Under nutritional stress conditions, TcVps15 and TcVps34 modify their subcellular distribution showing a partial co‐localization in autophagosomes with TcAtg8.1 and using an active site TcVps15‐mutated version (TcVps15‐K219D‐HA) we demonstrated that this relocalization depends on the TcVps15 catalytic activity. Overexpression of TcVps15‐HA and TcVps15‐K219D‐HA also leads to increased accumulation of monodansylcadaverine (MDC) in autophagic vacuoles under nutritional stress conditions compared to wild‐type cells. In addition, the MDC‐specific activity shows to be significantly higher in TcVps15‐HA overexpressing cells when compared with TcVps15‐K219D‐HA. Our results reveal for the first time a role of TcVps15 as a key regulator of TcVps34 enzymatic activity and implicate the TcVps15‐Vps34 complex in autophagy in T. cruzi, exposing a new key pathway to explore novel chemotherapeutic targets.
    Keywords Trypanosoma cruzi ; active sites ; amino acids ; autophagy ; catalytic activity ; cell membranes ; drug therapy ; energy ; enzyme activity ; eukaryotic cells ; malnutrition ; parasites ; pathogenicity ; phosphatidylinositol 3-kinase ; proteins ; protists ; vacuoles
    Language English
    Dates of publication 2017-05
    Size p. 308-321.
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 1147218-2
    ISSN 1550-7408 ; 1066-5234
    ISSN (online) 1550-7408
    ISSN 1066-5234
    DOI 10.1111/jeu.12367
    Database NAL-Catalogue (AGRICOLA)

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  3. Article: TbVps15 is required for vesicular transport and cytokinesis in Trypanosoma brucei

    Schoijet, Alejandra C / Kildare Miranda / Tamara Sternlieb / Nadia M. Barrera / Wendell Girard-Dias / Wanderley de Souza / Guillermo D. Alonso

    Molecular and biochemical parasitology. 2017,

    2017  

    Abstract: The class III phosphatidylinositol 3-kinase (PI3K) Vps34 is an important regulator of key cellular functions, including cell growth, survival, intracellular trafficking, autophagy and nutrient sensing. In yeast, Vps34 is associated with the putative ... ...

    Abstract The class III phosphatidylinositol 3-kinase (PI3K) Vps34 is an important regulator of key cellular functions, including cell growth, survival, intracellular trafficking, autophagy and nutrient sensing. In yeast, Vps34 is associated with the putative serine/threonine protein kinase Vps15, however, its role in signaling has not been deeply evaluated. Here, we have identified the Vps15 orthologue in Trypanosoma brucei, named TbVps15. Knockdown of TbVps15 expression by interference RNA resulted in inhibition of cell growth and blockage of cytokinesis. Scanning electron microcopy revealed a variety of morphological abnormalities, with enlarged parasites and dividing cells that often exhibited a detached flagellum. Transmission electron microscopy analysis of TbVps15 RNAi cells showed an increase in intracellular vacuoles of the endomembrane system and some cells displayed an enlargement of the flagellar pocket, a common feature of cells defective in endocytosis. Moreover, uptake of dextran, transferrin and Concanavalin A was impaired. Finally, TbVps15 downregulation affected the PI3K activity, supporting the hypothesis that TbVps15 and TbVps34 form a complex as occurs in other organisms. In summary, we propose that TbVps15 has a role in the maintenance of cytokinesis, endocytosis and intracellular trafficking in T. brucei.
    Keywords RNA interference ; Trypanosoma brucei ; autophagy ; cell growth ; concanavalin A ; cytokinesis ; dextran ; endomembrane system ; flagellum ; parasites ; phosphatidylinositol 3-kinase ; physiological transport ; protein-serine-threonine kinases ; threonine ; transferrin ; transmission electron microscopy ; vacuoles ; yeasts
    Language English
    Size p. .
    Publishing place Elsevier B.V.
    Document type Article
    Note Pre-press version
    ZDB-ID 756166-0
    ISSN 1872-9428 ; 0166-6851
    ISSN (online) 1872-9428
    ISSN 0166-6851
    DOI 10.1016/j.molbiopara.2017.11.004
    Database NAL-Catalogue (AGRICOLA)

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