Browsing by Author "Diaz, Jheimmy"

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    A new role for HERPUD1 and ERAD activation in osteoblast differentiation and mineralization
    (2018) Americo-Da-Silva, Luan; Diaz, Jheimmy; Bustamante, Mario; Mancilla, Georthan; Oyarzun, Ingrid; Verdejo Pinochet, Hugo; Quiroga Lagos, Clara Rosa
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    Ctdnep1 and Eps8L2 regulate dorsal actin cables for nuclear positioning during cell migration
    (2021) Calero-Cuenca, Francisco J.; Osorio, Daniel S.; Carvalho-Marques, Sofia; Sridhara, Sreerama Chaitanya; Oliveira, Luis M.; Jiao, Yue; Diaz, Jheimmy; Janota, Catia S.; Cadot, Bruno; Gomes, Edgar R.
    Cells actively position their nuclei within the cytoplasm for multiple cellular and physiological functions.(1-3) Consequently, nuclear mispositioning is usually associated with cell dysfunction and disease, from muscular disorders to cancermetastasis.(4-7) Different cell types position their nuclei away from the leading edge during cell migration.(8-11) In migrating fibroblasts, nuclear positioning is driven by an actin retrograde flow originated at the leading edge that drives dorsal actin cables away from the leading edge. The dorsal actin cables connect to the nuclear envelope by the linker of nucleoskeleton and cytoskeleton (LINC) complex on transmembrane actin-associated nuclear (TAN) lines.(12-14) Dorsal actin cables are required for the formation of TAN lines. How dorsal actin cables are organized to promote TAN lines formation is unknown. Here, we report a role for Ctdnep1/Dullard, a nuclear envelope phosphatase,(15-22) and the actin regulator Eps8L2(23-25) on nuclear positioning and cell migration. We demonstrate that Ctdnep1 and Eps8L2 directly interact, and this interaction is important for nuclear positioning and cell migration. We also show that Ctdnep1 and Eps8L2 are involved in the formation and thickness of dorsal actin cables required for TAN lines engagement during nuclear movement. We propose that Ctdnep1-Eps8L2 interaction regulates dorsal actin cables for nuclear movement during cell migration.
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    Ecm29-Dependent Proteasome Localization Regulates Cytoskeleton Remodeling at the Immune Synapse
    (2021) Ibanez-Vega, Jorge; Del Valle, Felipe; Saez, Juan Jose; Guzman, Fanny; Diaz, Jheimmy; Soza, Andrea; Yuseff, Maria Isabel
    The formation of an immune synapse (IS) enables B cells to capture membrane-tethered antigens, where cortical actin cytoskeleton remodeling regulates cell spreading and depletion of F-actin at the centrosome promotes the recruitment of lysosomes to facilitate antigen extraction. How B cells regulate both pools of actin, remains poorly understood. We report here that decreased F-actin at the centrosome and IS relies on the distribution of the proteasome, regulated by Ecm29. Silencing Ecm29 decreases the proteasome pool associated to the centrosome of B cells and shifts its accumulation to the cell cortex and IS. Accordingly, Ecm29-silenced B cells display increased F-actin at the centrosome, impaired centrosome and lysosome repositioning to the IS and defective antigen extraction and presentation. Ecm29-silenced B cells, which accumulate higher levels of proteasome at the cell cortex, display decreased actin retrograde flow in lamellipodia and enhanced spreading responses. Our findings support a model where B the asymmetric distribution of the proteasome, mediated by Ecm29, coordinates actin dynamics at the centrosome and the IS, promoting lysosome recruitment and cell spreading.
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    Functional analysis of the endoxylanase B (xynB) promoter from Penicillium purpurogenum
    (2008) Diaz, Jheimmy; Chavez, Renato; Larrondo, Luis F.; Eyzaguirre, Jaime; Bull, Paulina
    In Penicillium purpurogenum, the gene encoding endoxylanase B (xynB) is highly expressed by xylan and repressed by glucose at the transcriptional level. The promoter of this gene has a modular structure, with eight putative XlnR binding sites in tandem (XlnR module), and upstream from them, four putative CreA binding sites (CreA module). Promoter fragments containing different modules were inserted into a plasmid, pAN49-1, which contains a basal fungal promoter linked to a reporter gene (lacZ) and its expression was studied in vivo in Aspergillus nidulans. The XlnR module is able to trigger high beta-galactosidase activity in the presence of xylan, but the lack of most XlnR sites notoriously reduces this enzymatic activity. No enzyme induction is observed if the orientation of the promoter fragment is inverted. The presence of the CreA module is necessary for glucose repression when beta-galactosidase activity is previously induced by xylan. However, when transformant strains containing the XlnR module but lacking all CreA sites were grown in glucose without pre-induction in xylan, a low beta-galactosidase activity was observed compared with the same transformants grown in xylan. These results agree with a double-lock regulatory mechanism for both direct and indirect repression of xylanolytic genes by glucose.
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    Role of HERPUD1 and ERAD activation during differentiation and mineralization of osteoblast in vitro
    (WILEY, 2017) Americo Da Silva, Luan; Diaz, Jheimmy; Bustamante, Mario; Mancilla, Georthan; Oyarzun, Ingrid; Memmel, Mia; Verdejo, Hugo; Quiroga, Clara
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    Vamp-7–dependent secretion at the immune synapse regulates antigen extraction and presentation in B-lymphocytes
    (2017) Obinoa, Dorian; Diaz, Jheimmy; Sáez, Juan José; Ibañez Vega, Jorge; Sáez, Pablo J.; Alamo, Martina; Lankar, Danielle; Yuseff Sepúlveda, María Isabel