Browsing by Author "Ibanez-Vega, Jorge"

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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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    Interferon-gamma ameliorates experimental autoimmune encephalomyelitis by inducing homeostatic adaptation of microglia
    (2023) Tichauer, Juan E.; Arellano, Gabriel; Acuna, Eric; Gonzalez, Luis F.; Kannaiyan, Nirmal R.; Murgas, Paola; Panadero-Medianero, Concepcion; Ibanez-Vega, Jorge; Burgos, Paula I.; Loda, Eileah; Miller, Stephen D.; Rossner, Moritz J.; Gebicke-Haerter, Peter J.; Naves, Rodrigo
    Compelling evidence has shown that interferon (IFN)-gamma has dual effects in multiple sclerosis and in its animal model of experimental autoimmune encephalomyelitis (EAE), with results supporting both a pathogenic and beneficial function. However, the mechanisms whereby IFN-gamma may promote neuroprotection in EAE and its effects on central nervous system (CNS)-resident cells have remained an enigma for more than 30 years. In this study, the impact of IFN-gamma at the peak of EAE, its effects on CNS infiltrating myeloid cells (MC) and microglia (MG), and the underlying cellular and molecular mechanisms were investigated. IFN-gamma administration resulted in disease amelioration and attenuation of neuroinflammation associated with significantly lower frequencies of CNS CD11b(+) myeloid cells and less infiltration of inflammatory cells and demyelination. A significant reduction in activated MG and enhanced resting MG was determined by flow cytometry and immunohistrochemistry. Primary MC/MG cultures obtained from the spinal cord of IFN-gamma-treated EAE mice that were ex vivo re-stimulated with a low dose (1 ng/ml) of IFN-gamma and neuroantigen, promoted a significantly higher induction of CD4(+) regulatory T (Treg) cells associated with increased transforming growth factor (TGF)-beta secretion. Additionally, IFN-gamma-treated primary MC/MG cultures produced significantly lower nitrite in response to LPS challenge than control MC/MG. IFN-gamma-treated EAE mice had a significantly higher frequency of CX3CR1(high) MC/MG and expressed lower levels of program death ligand 1 (PD-L1) than PBS-treated mice. Most CX3CR1(high)PD-L1(low)CD11b(+)Ly6G(-) cells expressed MG markers (Tmem119, Sall2, and P2ry12), indicating that they represented an enriched MG subset (CX3CR1(high)PD-L1(low) MG). Amelioration of clinical symptoms and induction of CX3CR1(high)PD-L1(low) MG by IFN-gamma were dependent on STAT-1. RNA-seq analyses revealed that in vivo treatment with IFN-gamma promoted the induction of homeostatic CX3CR1(high)PD-L1(low) MG, upregulating the expression of genes associated with tolerogenic and anti-inflammatory roles and down-regulating pro-inflammatory genes. These analyses highlight the master role that IFN-gamma plays in regulating microglial activity and provide new insights into the cellular and molecular mechanisms involved in the therapeutic activity of IFN-gamma in EAE.