Browsing by Author "Soares, Helena"
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- Antagonist G-targeted liposomes for improved delivery of anticancer drugs in small cell lung carcinomaPublication . Carvalheiro, Manuela; Ferreira-Silva, Margarida; Holovanchuk, Denys; Marinho, H. Susana; Moreira, João Nuno; Soares, Helena; Corvo, M. Luisa; Cruz, Maria Eugénia M.Ligand-mediated targeted liposomes have the potential to increase the therapeutic efficacy of anticancer drugs. This work aimed to evaluate the ability of antagonist G, a peptide targeting agent capable of blocking the action of multiple neuropeptides, to selectivity improve targeting and internalization of liposomal formulations (long-circulating liposomes, LCL, and stabilized antisense lipid particles containing ionizable amino lipid, SALP) to H69 and H82 small cell lung carcinoma (SCLC) cell lines. Antagonist G-targeted LCL and SALP were prepared by two different methods (either by direct covalent linkage at activated PEG grafted onto the liposomal surface or by post-insertion of DSPE-PEG-antagonist-G-conjugates into pre-formed liposomes). Association of the liposomal formulations with target SCLC cells was studied by fluorescence microscopy using fluorescence-labeled liposomes and confirmed quantitatively with [3H]-CHE-labelled liposomes. An antisense oligodeoxynucleotide against the overexpressed oncogene c-myc(as(c-myc)) was efficiently loaded into SALP formulations, the encapsulation efficiency decreased due to the inclusion of the targeting ligand. Also, liposome size was affected by as(c-myc) physical-chemical properties. The amount of antagonist G linked to the surface of the liposomal formulations was dependent on the coupling method and lipid composition used. Covalent attachment of antagonist G increased liposomes' cellular association and internalization via receptor-mediated and clathrin-dependent endocytosis, as assessed in SCLC cell lines. Biodistribution studies in healthy mice revealed a preferential lung accumulation of antagonist G-targeted SALP as compared to the non-targeted counterpart. Lung levels of the former were up to 3-fold higher 24 h after administration, highlighting their potential to be used as delivery vectors for SCLC treatment.
- Apicomplexans pulling the strings: manipulation of the host cell cytoskeleton dynamicsPublication . Cardoso, Rita; Soares, Helena; Hemphill, Andrew; Leitão, AlexandreInvasive stages of apicomplexan parasites require a host cell to survive, proliferate and advance to the next life cycle stage. Once invasion is achieved, apicomplexans interact closely with the host cell cytoskeleton, but in many cases the different species have evolved distinct mechanisms and pathways to modulate the structural organization of cytoskeletal filaments. The host cell cytoskeleton is a complex network, largely, but not exclusively, composed of microtubules, actin microfilaments and intermediate filaments, all of which are modulated by associated proteins, and it is involved in diverse functions including maintenance of cell morphology and mechanical support, migration, signal transduction, nutrient uptake, membrane and organelle trafficking and cell division. The ability of apicomplexans to modulate the cytoskeleton to their own advantage is clearly beneficial. We here review different aspects of the interactions of apicomplexans with the three main cytoskeletal filament types, provide information on the currently known parasite effector proteins and respective host cell targets involved, and how these interactions modulate the host cell physiology. Some of these findings could provide novel targets that could be exploited for the development of preventive and/or therapeutic strategies.
- Autoinhibition of TBCB regulates EB1-mediated microtubule dynamicsPublication . Carranza, Gerardo; Castaño, Raquel; Fanarraga, Mónica L.; Villegas, Juan Carlos; Gonçalves, João; Soares, Helena; Avila, Jesus; Marenchino, Marco; Campos-Olivas, Ramón; Montoya, Guillermo; Zabala, Juan CarlosTubulin cofactors (TBCs) participate in the folding, dimerization, and dissociation pathways of the tubulin dimer. Among them, TBCB and TBCE are two CAP-Gly domain-containing proteins that together efficiently interact with and dissociate the tubulin dimer. In the study reported here we showed that TBCB localizes at spindle and midzone microtubules during mitosis. Furthermore, the motif DEI/M-COO− present in TBCB, which is similar to the EEY/F-COO− element characteristic of EB proteins, CLIP-170, and α-tubulin, is required for TBCE–TBCB heterodimer formation and thus for tubulin dimer dissociation. This motif is responsible for TBCB autoinhibition, and our analysis suggests that TBCB is a monomer in solution. Mutants of TBCB lacking this motif are derepressed and induce microtubule depolymerization through an interaction with EB1 associated with microtubule tips. TBCB is also able to bind to the chaperonin complex CCT containing α-tubulin, suggesting that it could escort tubulin to facilitate its folding and dimerization, recycling or degradation.
- Balancing act: tubulin glutamylation and microtubule dynamics in Toxoplasma gondiiPublication . Delgado, Inês; Gonçalves, João; Fernandes, Rita; Zúquete, Sara; Basto, Afonso P.; Leitão, Alexandre; Soares, Helena; Nolasco, SofiaThe success of the intracellular parasite Toxoplasma gondii in invading host cells relies on the apical complex, a specialized microtubule cytoskeleton structure associated with secretory organelles. The T. gondii genome encodes three isoforms of both α- and β-tubulin, which undergo specific post-translational modifications (PTMs), altering the biochemical and biophysical proprieties of microtubules and modulating their interaction with associated proteins. Tubulin PTMs represent a powerful and evolutionarily conserved mechanism for generating tubulin diversity, forming a biochemical 'tubulin code' interpretable by microtubule-interacting factors. T. gondii exhibits various tubulin PTMs, including α-tubulin acetylation, α-tubulin detyrosination, Δ5α-tubulin, Δ2α-tubulin, α- and β-tubulin polyglutamylation, and α- and β-tubulin methylation. Tubulin glutamylation emerges as a key player in microtubule remodeling in Toxoplasma, regulating stability, dynamics, interaction with motor proteins, and severing enzymes. The balance of tubulin glutamylation is maintained through the coordinated action of polyglutamylases and deglutamylating enzymes. This work reviews and discusses current knowledge on T. gondii tubulin glutamylation. Through in silico identification of protein orthologs, we update the recognition of putative proteins related to glutamylation, contributing to a deeper understanding of its role in T. gondii biology.
- Balancing act: tubulin glutamylation and microtubule dynamics in Toxoplasma gondiiPublication . Delgado, Inês L.S.; Gonçalves, João; Fernandes, Rita; Zúquete, Sara; Basto, Afonso P.; Leitão, Alexandre; Soares, Helena; Nolasco, SofiaThe success of Toxoplasma gondii (intracellular parasite) host cell invasion relies on the apical complex, a specialized microtubule cytoskeleton structure associated with secretory organelles. The genome encodes three isoforms of both α- and β-tubulin which are altered by specific post-translational modifications (PTMs), changing the biochemical/biophysical proprieties of microtubules, and modulating their interaction with associated proteins. Tubulin PTMs are a powerful and evolutionarily conserved mechanism to generate tubulin diversity, forming a biochemical ‘tubulin code’ that can be ‘read’ by microtubule-interacting factors. The T. gondii tubulin PTMs are: α-tubulin acetylation, α-tubulin detyrosination, Δ5α-tubulin, Δ2α-tubulin, α- and β-tubulin polyglutamylation, and α- and α-tubulin methylation. Tubulin glutamylation is a key candidate to assist microtubule remodeling in Toxoplasma, being involved in the regulation of microtubule stability, dynamics, interaction with motor proteins, and severing enzymes. The correct balance of tubulin glutamylation is achieved by the coordinated action of polyglutamylases and deglutamylating enzymes. In this work, we will review and discuss the current knowledge on T. gondii tubulin glutamylation. By in silico identification of mammalian protein orthologs, we explored and updated the identification of putative proteins related to glutamylation, contributing to a better understanding of the role of tubulin glutamylation in T. gondii.
- Besnoitia besnoiti and Toxoplasma gondii: two apicomplexan strategies to manipulate the host cell centrosome and Golgi apparatusPublication . Cardoso, Rita; Nolasco, Sofia; Gonçalves, João; Cortes, Helder C.; Leitão, Alexandre; Soares, HelenaBesnoitia besnoiti and Toxoplasma gondii are two closely related parasites that interact with the host cell microtubule cytoskeleton during host cell invasion. Here we studied the relationship between the ability of these parasites to invade and to recruit the host cell centrosome and the Golgi apparatus. We observed that T. gondii recruits the host cell centrosome towards the parasitophorous vacuole (PV), whereas B. besnoiti does not. Notably, both parasites recruit the host Golgi apparatus to the PV but its organization is affected in different ways. We also investigated the impact of depleting and over-expressing the host centrosomal protein TBCCD1, involved in centrosome positioning and Golgi apparatus integrity, on the ability of these parasites to invade and replicate. Toxoplasma gondii replication rate decreases in cells over-expressing TBCCD1 but not in TBCCD1-depleted cells; while for B. besnoiti no differences were found. However, B. besnoiti promotes a reorganization of the Golgi ribbon previously fragmented by TBCCD1 depletion. These results suggest that successful establishment of PVs in the host cell requires modulation of the Golgi apparatus which probably involves modifications in microtubule cytoskeleton organization and dynamics. These differences in how T. gondii and B. besnoiti interact with their host cells may indicate different evolutionary paths.
- CCTαPublication . Soares, Helena; Nolasco, SofiaIn the cell, the correct folding of many proteins depends on the function of preexisting ones known as Molecular Chaperones (for a review see Hartl and Hayer-Hartl 2009). These, were defined as proteins that bind to and stabilize an otherwise unstable conformation of another protein, and by controlling binding and release, facilitate its correct fate in vivo, be it folding, oligomeric assembly, transport to a particular subcellular compartment, or disposal by degradation. Molecular chaperones do not convey steric information specifying correct folding: instead, they prevent incorrect interactions within and between nonnative peptides, thus typically increasing the yield but not the rate of folding reactions. Molecular chaperones are ubiquitous and comprise several protein families that are structurally unrelated (Hartl and Hayer-Hartl 2009). The Hsp70s and the Chaperonin families have been extensively studied.
- CCTα and CCTδ chaperonin subunits are essential and required for cilia assembly and maintenance in TetrahymenaPublication . Seixas, Cecília; Cruto, Teresa; Tavares, Alexandra; Gaertig, Jacek; Soares, HelenaBackground - The eukaryotic cytosolic chaperonin CCT is a hetero-oligomeric complex formed by two rings connected back-to-back, each composed of eight distinct subunits (CCTalpha to CCTzeta). CCT complex mediates the folding, of a wide range of newly synthesised proteins including tubulin (alpha, beta and gamma) and actin, as quantitatively major substrates. Methodology/Principal findings - We disrupted the genes encoding CCTalpha and CCTdelta subunits in the ciliate Tetrahymena. Cells lacking the zygotic expression of either CCTalpha or CCTdelta showed a loss of cell body microtubules, failed to assemble new cilia and died within 2 cell cycles. We also show that loss of CCT subunit activity leads to axoneme shortening and splaying of tips of axonemal microtubules. An epitope-tagged CCTalpha rescued the gene knockout phenotype and localized primarily to the tips of cilia. A mutation in CCTalpha, G346E, at a residue also present in the related protein implicated in the Bardet Biedel Syndrome, BBS6, also caused defects in cilia and impaired CCTalpha localization in cilia. Conclusions/Significance - Our results demonstrate that the CCT subunits are essential and required for ciliary assembly and maintenance of axoneme structure, especially at the tips of cilia.
- Cellular polarity in aging: role of redox regulation and nutritionPublication . Soares, Helena; Marinho, H. Susana; Real, Carla; Antunes, FernandoCellular polarity concerns the spatial asymmetric organization of cellular components and structures. Such organization is important not only for biological behavior at the individual cell level, but also for the 3D organization of tissues and organs in living organisms. Processes like cell migration and motility, asymmetric inheritance, and spatial organization of daughter cells in tissues are all dependent of cell polarity. Many of these processes are compromised during aging and cellular senescence. For example, permeability epithelium barriers are leakier during aging; elderly people have impaired vascular function and increased frequency of cancer, and asymmetrical inheritance is compromised in senescent cells, including stem cells. Here, we review the cellular regulation of polarity, as well as the signaling mechanisms and respective redox regulation of the pathways involved in defining cellular polarity. Emphasis will be put on the role of cytoskeleton and the AMP-activated protein kinase pathway. We also discuss how nutrients can affect polarity-dependent processes, both by direct exposure of the gastrointestinal epithelium to nutrients and by indirect effects elicited by the metabolism of nutrients, such as activation of antioxidant response and phase-II detoxification enzymes through the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In summary, cellular polarity emerges as a key process whose redox deregulation is hypothesized to have a central role in aging and cellular senescence.
- Centrosome positioning and development of ciliopathies: role of the human centrosomal protein TBCCD1Publication . Carmona, Bruno; Camelo, Carolina; Mehraz, Manon; Lemullois, Michel; Ferreira, David C.; Nolasco, Sofia; Lince-Faria, Mariana; Marinho, H. Susana; Bettencourt-Dias, Mónica; Tassin, Anne-Marie; Soares, HelenaAims/Context: Primary cilia are specialized microtubule-based signaling organelles that convey extracellular signaling and cellular polarity into a cellular response. Defects in primary cilia assembly/function cause severe diseases known as ciliopathies, typified by clinical manifestations, like infertility, obesity, brain problems, blindness, and kidney cysts. Primary cilia assembly entails centrosome migration to the plasma membrane where a centriole docks, maturates into a basal body (BB), and assembles the cilia axoneme. The human centrosomal TBCCD1 is a critical factor in centrosome positioning previously identified by us. Our aim is to discover the mechanisms/signals required for the correct positioning of the centrosome during cilia assembly, and how these mechanisms, when compromised, are related to ciliopathies. Methods: The proximity-dependent identification (BioID) assay was used to screen for TBCCD1 interactors. Immunofluorescent and super-resolution microscopy, as well as Western blot, were used to study the levels and cellular localization of the identified TBCCD1 interactors in human RPE1 cells overexpressing or depleted of TBCCD1. To study the impact of TBCCD1 knockdown in motile cilia the ciliate Paramecium, containing ∼3,000 motile cilia, was used. Results: Our BioID screen for TBCCD1 interactors identified several well-known proteins encoded by ciliopathy genes, e.g. the centrosomal protein OFD1 involved in the Orofacial-Digital Syndrome. We show that TBCCD1 knockdown and overexpression in RPE1 cells affects OFD1 distribution. Super-resolution microscopy shows TBCCD1 is localized at the distal region of the centrosome and that its depletion dramatically affects the centrosome subdistal protein CEP170, a component of cilia basal feet. In Paramecium, the TBCCD1 knockdown causes abnormal BB-associated structures organization and anomalous BB positioning/anchoring defects. Conclusions: Our data support a role for TBCCD1 in the maintenance of centrosome structure and in BB anchoring at the cell membrane during ciliogenesis. TBCCD1 is emerging as a novel protein with a role in human ciliopathies.