Navegando por Palavras-chave "actin"

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    Candida albicans: The Ability to Invade Epithelial Cells and Survive under Oxidative Stress Is Unlinked to Hyphal Length
    (Frontiers Media Sa, 2017) Maza, Paloma K. [UNIFESP]; Bonfim-Melo, Alexis [UNIFESP]; Padovan, Ana C. B. [UNIFESP]; Mortara, Renato A. [UNIFESP]; Orikaza, Cristina M. [UNIFESP]; Damas Ramos, Lilian M.; Moura, Tauany R.; Soriani, Frederico M.; Almeida, Ricardo S.; Suzuki, Erika [UNIFESP]; Bahia, Diana [UNIFESP]
    In its hyphal form, Candida albicans invades epithelial and endothelial cells by two distinct mechanisms: active penetration and induced endocytosis. The latter is dependent on a reorganization of the host cytoskeleton (actin/cortactin recruitment), whilst active penetration does not rely on the host's cellular machinery. The first obstacle for the fungus to reach deep tissues is the epithelial barrier and this interaction is crucial for commensal growth, fungal pathogenicity and host defense. This study aimed to characterize in vitro epithelial HeLa cell invasion by four different isolates of C. albicans with distinct clinical backgrounds, including a C. albicans SC5314 reference strain. All isolates invaded HeLa cells, recruited actin and cortactin, and induced the phosphorylation of both Src-family kinases (SFK) and cortactin. Curiously, L3881 isolated from blood culture of a patient exhibited the highest resistance to oxidative stress, although this isolate showed reduced hyphal length and displayed the lowest cell damage and invasion rates. Collectively, these data suggest that the ability of C. albicans to invade HeLa cells, and to reach and adapt to the host's blood, including resistance to oxidative stress, may be independent of hyphal length.
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    The distribution of motor proteins in the muscles and flame cells of the Schistosoma mansoni miracidium and primary sporocyst
    (Cambridge Univ Press, 2006-09-01) Bahia, Daniella Marcia Maranhão [UNIFESP]; Avelar, L. G. A.; Vigorosi, F.; Cioli, D.; Oliveira, G. C.; Mortara, R. A.; Universidade Federal de São Paulo (UNIFESP); Fiocruz MS; Inst Cell Biol
    Schistosoma mansoni eggs, miracidia and primary sporocysts were labelled with phalloidin-rhodamine to visualize filamentous actin structures. Analysis of these forms by confocal fluorescence microscopy revealed the presence of previously well-defined circular and longitudinal muscle layers. Besides these muscular layers that sustain and provide motility to these parasite forms, we found in these 3 consecutive developmental stages of the parasite previously unidentified actin-rich tubular structures. in the 3 forms, 4 actin-rich tubules could be observed by optical sectioning underneath the well-developed muscle layers. the tubules appear in pairs, transversal to the length of the parasite, and located towards the extremities. By using an anti-flame cell specific antibody we confirmed that the tubules co-localize with flame cells and also determined that the tubule core is filled with microtubules. the additional presence of myosin in these tubules strongly suggests that they are contractile structures.
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    Rac1/WAVE2 and Cdc42/N-WASP Participation in Actin-Dependent Host Cell Invasion by Extracellular Amastigotes of Trypanosoma cruzi
    (Frontiers Media Sa, 2018) Bonfim-Melo, Alexis [UNIFESP]; Ferreira, Eden R. [UNIFESP]; Mortara, Renato A. [UNIFESP]
    This study evaluated the participation of host cell Rho-family GTPases and their effector proteins in the actin-dependent invasion by Trypanosoma cruzi extracellular amastigotes (EAs). We observed that all proteins were recruited and colocalized with actin at EA invasion sites in live or fixed cells. EA internalization was inhibited in cells depleted in Rac1, N-WASP, and WAVE2. Time-lapse experiments with Rac1, N-WASP and WAVE2 depleted cells revealed that EA internalization kinetics is delayed even though no differences were observed in the proportion of EA-induced actin recruitment in these groups. Overexpression of constitutively active constructs of Rac1 and RhoA altered the morphology of actin recruitments to EA invasion sites. Additionally, EA internalization was increased in cells overexpressing CA-Rac1 but inhibited in cells overexpressing CA-RhoA. WT-Cdc42 expression increased EA internalization, but curiously, CA-Cdc42 inhibited it. Altogether, these results corroborate the hypothesis of EA internalization in non-phagocytic cells by a phagocytosis-like mechanism and present Rac1 as the key Rho-family GTPase in this process.