Browsing by Author "Pinto, Francisco"
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- Opi1p translocation to the nucleus is regulated by hydrogen peroxide in Saccharomyces cerevisiaePublication . Camelo, Carolina; Vilas-Boas, Filipe; Cepeda, Andreia Pereira; Real, Carla; Barros-Martins, Joana; Pinto, Francisco; Soares, Helena; Marinho, H. Susana; Cyrne, LuisaDuring exposure of yeast cells to low levels of hydrogen peroxide (H2 O2 ), the expression of several genes is regulated for cells to adapt to the surrounding oxidative environment. Such adaptation involves modification of plasma membrane lipid composition, reorganization of ergosterol-rich microdomains and altered gene expression of proteins involved in lipid and vesicle traffic, to decrease permeability to exogenous H2 O2. Opi1p is a transcriptional repressor that is inactive when present at the nuclear membrane/endoplasmic reticulum, but represseses transcription of inositol upstream activating sequence (UASINO )-containing genes, many of which are involved in the synthesis of phospholipids and fatty acids, when it is translocated to the nucleus. We investigated whether H2 O2 in concentrations inducing adaptation regulates Opi1p function. We found that, in the presence of H2 O2, GFP-Opi1p fusion protein translocates to the nucleus and, concomitantly, the expression of UASINO -containing genes is affected. We also investigated whether cysteine residues of Opi1p were implicated in the H2 O2 -mediated translocation of this protein to the nucleus and identified cysteine residue 159 as essential for this process. Our work shows that Opi1p is redox-regulated and establishes a new mechanism of gene regulation involving Opi1p, which is important for adaptation to H2 O2 in yeast cells.
- The maintenance of centriole appendages and motile cilia basal body anchoring relies on TBCCD1Publication . Carmona, Bruno; Camelo, Carolina; Mehraz, Manon; Lemullois, Michel; Faria, Mariana Lince; Coyaud, Étienne; Marinho, H. Susana; Gonçalves, João; Nolasco, Sofia; Pinto, Francisco; Raught, Brian; Tassin, Anne-Marie; Koll, France; Soares, HelenaCentrosomes are organelles consisting of two structurally and functionally distinct centrioles, with the mother centriole having complex distal (DA) and subdistal appendages (SDA). Despite their importance, how appendages are assembled and maintained remains unclear. This study investigated human TBCCD1, a centrosomal protein essential for centrosome positioning, to uncover its localization and role at centrioles. We found that TBCCD1 localizes at both proximal and distal regions of the two centrioles, forming a complex structure spanning from SDA to DA and extending inside and outside the centriole lumen. TBCCD1 depletion caused centrosome mispositioning, which was partially rescued by taxol, and the loss of microtubules (MTs) anchored to centrosomes. TBCCD1 depletion also reduced levels of SDA proteins involved in MT anchoring such as Centriolin/CEP110, Ninein, and CEP170. Additionally, TBCCD1 was essential for the correct positioning of motile cilia basal bodies and associated structures in Paramecium. This study reveals that TBCCD1 is an evolutionarily conserved protein essential for centriole and basal body localization and appendage assembly and maintenance. A BioID screening also linked TBCCD1 to ciliopathy-associated protein networks.
- Unraveling the role of TBCCD1 protein on cell size control: the regulation of cytoskeleton dynamics and cell junctionsPublication . Camelo, Carolina; Peneda, Catarina; Coyaud, Étienne; Raught, Brian; Câmara, Ana I.; Carmona, Bruno; Pinto, Francisco; Narinho, H. Susana; Soares, HelenaDuring their lifetime most cells maintain their size. There is increasing evidence showing that this process may be dynamic and that cells can adapt their size in response to external signals and changes in the environment [1], which strongly suggests that cell size is regulated. Both Hippo and IGF/PI3K/AKT/mTORC1 pathways have been described as being involved in cell size/growth control [1]. Interestingly, these pathways are in a cross-talk with others involved and/or dependent on cellular polarity [2]. Our group characterized a centrosomal protein, TBCCD1 (TBCC domain – containing human protein 1) which, when depleted in human retinal epithelial (RPE–1) cells, leads to an abnormal localization of the centrosome at the cell periphery accompanied by the fragmentation of the Golgi apparatus, resulting in the disruption of the intrinsic cell polarity axis “Nucleus-Centrosome-Golgi Apparatus”. Moreover, TBCCD1 – depleted cells are larger, slower and have a lower efficiency in primary cilia assembly than control cells [3]. We identified the TBCCD1 interactome that showed that most of its partners are involved in cell polarity. Furthermore, most of them participate in the formation/maintenance of cell junctions, which are main regulators of cell polarity in epithelia and are upstream of pathways, like Hippo pathway. We also observed that TBCCD1 overexpression affects tubulin acetylation, which supports our results showing that some of the partners are involved in the regulation of the cytoskeleton dynamics, which may affect cell size. Therefore, it is tempting to hypothesize that the mechanisms involved in the establishment of intrinsic cell polarity may also directly/indirectly participate in the regulation of cell size.