Browsing by Author "Vitorino, Rui"
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- Effects of chitooligosaccharides on human red blood cell morphology and membrane protein structurePublication . Fernandes, João C.; Eaton, Peter; Nascimento, Henrique; Belo, Luís; Rocha, Susana; Vitorino, Rui; Amado, Francisco; Gomes, Joana; Santos-Silva, Alice; Pintado, Manuela E.; Malcata, F. XavierRecent studies of chitosan have increased the interest in its conversion to chitooligosaccharides (COSs) because these compounds are water-soluble and have potential use in several biomedical applications. Furthermore, such oligomers may be more advantageous than chitosans because of their much higher absorption profiles at the intestinal level, which permit their facilitated access to systemic circulation and potential distribution throughout the entire human body. In that perspective, it is important to clarify their effect on blood further, namely, on human red blood cells (RBCs). The aim of this work was thus to study the effect of two COS mixtures with different molecular weight (MW) ranges, <3 and <5 kDa, at various concentrations (5.0-0.005 mg/mL) on human RBCs. The interactions of these two mixtures with RBC membrane proteins and with hemoglobin were assessed, and the RBC morphology and surface structure were analyzed by optical microscopy (OM) and atomic force microscopy (AFM). In the presence of either COS mixture, no significant hemolysis was observed; however, at COS concentrations >0.1 mg/mL, changes in membrane binding hemoglobin were observed. Membrane protein changes were also observed with increasing COS concentration, including a reduction in both α- and β-spectrin and in band 3 protein, and the development of three new protein bands: peroxiredoxin 2, calmodulin, and hemoglobin chains. Morphologic evaluation by OM showed that at high concentrations COSs interact with RBCs, leading to RBC adhesion, aggregation, or both. An increase in the roughness of the RBC surface with increasing COS concentration was observed by AFM. Overall, these findings suggest that COS damage to RBCs was dependent on the COS MW and concentration, and significant damage resulted from either a higher MW or a greater concentration (>0.1 mg/mL).
- Influenza A virus propagation requires the activation of the unfolded protein response and the accumulation of insoluble protein aggregatesPublication . Marques, Mariana; Ramos, Bruno; Albuquerque, Hélio; Pereira, Marisa; Ribeiro, Diana Roberta; Nunes, Alexandre; Sarabando, Jéssica; Brás, Daniela; Ferreira, Ana Rita; Vitorino, Rui; Amorim, Maria João; Silva, Artur M. S.; Soares, Ana Raquel; Ribeiro, DanielaInfluenza A virus (IAV) employs multiple strategies to manipulate cellular mechanisms and support proper virion formation and propagation. In this study, we performed a detailed analysis of the interplay between IAV and the host cells’ proteostasis throughout the entire infectious cycle. We reveal that IAV infection activates the inositol requiring enzyme 1 (IRE1) branch of the unfolded protein response, and that this activation is important for an efficient infection. We further observed the accumulation of virus-induced insoluble protein aggregates, containing both viral and host proteins, associated with a dysregulation of the host cell RNA metabolism. Our data indicate that this accumulation is important for IAV propagation and favors the final steps of the infection cycle, more specifically the virion assembly. These findings reveal additional mechanisms by which IAV disrupts host proteostasis and uncovers new cellular targets that can be explored for the development of host-directed antiviral strategies.