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Figure S1 shows the numbers of dendritic cells, macrophages and B cells in the colon, and the numbers of dendritic cells in the mesenteric lymph nodes of control and cKO mice treated with AOM and DSS.

The escape of cancer cells from host immunosurveillance involves a shift in immune responses, including an imbalance in Th1 and Th2 cells. A Th1-dominated immune response predicts positive outcomes in colorectal cancer. The E3 ubiquitin ligase, Asb2α, is expressed in Th2 cells, but its roles in T-cell maturation and cancer are unclear. We provide evidence that the Th2 master regulator, Gata3, induces Asb2. Loss of Asb2 did not affect Th differentiation ex vivo, but reduced IL4 production from Th2 cells. We found that high ASB2 expression was associated with poor outcome in colorectal cancer. Loss of Asb2 from hematopoietic cells promoted a Th1 response and attenuated colitis-associated tumorigenesis in mice. Diminished Th2 function correlated with increased IFNγ production and an enhanced type 1 antitumor immune response in Asb2-deficient mice. Our work suggests that Asb2α promotes a Th2 phenotype in vivo, which in turn is associated with tumor progression in a mouse model of colitis.

Macrophages are essential for HIV-1 pathogenesis and represent major viral reservoirs. Therefore, it is critical to understand macrophage infection, especially in tissue macrophages, which are widely infected in vivo, but poorly permissive to cell-free infection. Although cell-to-cell transmission of HIV-1 is a determinant mode of macrophage infection in vivo, how HIV-1 transfers toward macrophages remains elusive. Here, we demonstrate that fusion of infected CD4+ T lymphocytes with human macrophages leads to their efficient and productive infection. Importantly, several tissue macrophage populations undergo this heterotypic cell fusion, including synovial, placental, lung alveolar, and tonsil macrophages. We also find that this mode of infection is modulated by the macrophage polarization state. This fusion process engages a specific short-lived adhesion structure and is controlled by the CD81 tetraspanin, which activates RhoA/ROCK-dependent actomyosin contractility in macrophages. Our study provides important insights into the mechanisms underlying infection of tissue-resident macrophages, and establishment of persistent cellular reservoirs in patients.

SummaryRegulated cell necrosis supports immune and anti-infectious strategies of the body; however, dysregulation of these processes drives pathological organ damage.Pseudomonas aeruginosaexpresses a phospholipase, ExoU that triggers pathological host cell necrosis through a poorly characterized pathway. Here, we investigated the molecular and cellular mechanisms of ExoU-mediated necrosis. We show that cellular peroxidised phospholipids enhance ExoU phospholipase activity, which drives necrosis of immune and non-immune cells. Conversely, both the endogenous lipid peroxidation regulator GPX4 and the pharmacological inhibition of lipid peroxidation delay ExoU-dependent cell necrosis and improve bacterial eliminationin vitroandin vivo. Our findings also pertain to the ExoU-related phospholipase from the bacterial pathogenBurkholderia thailandensis, suggesting that exploitation of peroxidised phospholipids might be a conserved virulence mechanism among various microbial phospholipases. Overall, our results identify an original lipid peroxidation-based virulence mechanism as a strong contributor of microbial phospholipase-driven pathology.

Regulated cell necrosis supports immune and anti-infectious strategies of the body; however, dysregulation of these processes drives pathological organ damage. Pseudomonas aeruginosa expresses a phospholipase, ExoU that triggers pathological host cell necrosis through a poorly characterized pathway. Here, we investigated the molecular and cellular mechanisms of ExoU-mediated necrosis. We show that cellular peroxidised phospholipids enhance ExoU phospholipase activity, which drives necrosis of immune and non-immune cells. Conversely, both the endogenous lipid peroxidation regulator GPX4 and the pharmacological inhibition of lipid peroxidation delay ExoU-dependent cell necrosis and improve bacterial elimination in vitro and in vivo. Our findings also pertain to the ExoU-related phospholipase from the bacterial pathogen Burkholderia thailandensis, suggesting that exploitation of peroxidised phospholipids might be a conserved virulence mechanism among various microbial phospholipases. Overall, our results identify an original lipid peroxidation-based virulence mechanism as a strong contributor of microbial phospholipase-driven pathology., Author summary Although a proper activation of various regulated cell necrosis confer a significant advantage against various infectious agents, their dysregulation drives host tissue damages that can end up with fatal sepsis. Specifically, 30% of the bacterial strains of Pseudomonas aeruginosa (P. aeruginosa) express the phospholipase A2-like toxin ExoU that is injected into host target cells through the Type-3 Secretion System. This toxin induces, through a yet unknown mechanism, a strong and fast necrotic cell death that supports fatal respiratory infections. Therefore, in this study, we sought to determine the cellular mechanisms by which ExoU triggers host cell necrosis. In this context, we found that ExoU exploits basal cellular phospholipid peroxidation to promote cell necrosis. Mechanistically, host cell lipid peroxidation stimulates ExoU phospholipase activity, which then triggers a pathological cell necrosis both in vitro and in vivo. Altogether, our results unveil that targeting host cell lipid peroxidation constitutes a virulence mechanism developed by microbial phospholipases, a process that contributes to P. aeruginosa-mediated pathology.

Mycobacterium tuberculosis (Mtb) regulates the macrophage metabolic state to thrive in the host, yet the responsible mechanisms remain elusive. Macrophage activation toward the microbicidal (M1) program depends on the HIF-1α-mediated metabolic shift from oxidative phosphorylation (OXPHOS) toward glycolysis. Here, we ask whether a tuberculosis (TB) microenvironment changes the M1 macrophage metabolic state. We expose M1 macrophages to the acellular fraction of tuberculous pleural effusions (TB-PEs) and find lower glycolytic activity, accompanied by elevated levels of OXPHOS and bacillary load, compared to controls. The eicosanoid fraction of TB-PE drives these metabolic alterations. HIF-1α stabilization reverts the effect of TB-PE by restoring M1 metabolism. Furthermore, Mtb-infected mice with stabilized HIF-1α display lower bacillary loads and a pronounced M1-like metabolic profile in alveolar macrophages (AMs). Collectively, we demonstrate that lipids from a TB-associated microenvironment alter the M1 macrophage metabolic reprogramming by hampering HIF-1α functions, thereby impairing control of Mtb infection. Fil: Marin Franco, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina. Centre National de la Recherche Scientifique; Francia Fil: Genoula, Melanie. Centre National de la Recherche Scientifique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina Fil: Corral, Dan. Université de Toulouse; Francia Fil: Duette, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; Argentina Fil: Ferreyra, Malena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina. Centre National de la Recherche Scientifique; Francia Fil: Maio, Mariano Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina Fil: Dolotowicz, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina Fil: Aparicio Trejo, Omar Emiliano. Universidad Nacional Autónoma de México. Instituto de Biología; México Fil: Patiño Martínez, Eduardo. Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional; México Fil: Charton, Alison. Université de Toulouse; Francia Fil: Métais, Arnaud. Université de Toulouse; Francia Fil: Fuentes, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina Fil: Soldan, Vanessa. Université de Toulouse; Francia Fil: Moraña, Eduardo José. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina Fil: Palmero, Domingo Juan. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina Fil: Ostrowski, Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; Argentina Fil: Schierloh, Pablo. Centre National de la Recherche Scientifique; Francia. Instituto de Bioquímica y Biología Molecular; Argentina. Universidad Nacional de Entre Ríos; Argentina Fil: Sánchez Torres, Carmen. Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional; México Fil: Hernández Pando, Rogelio. Instituto Nacional de Ciencias Médicas y Nutrición; México Fil: Pedraza Chaverri, José. Universidad Nacional Autónoma de México. Instituto de Biología; México Fil: Rombouts, Yoann. Université de Toulouse; Francia Fil: Hudrisier, Denis. Université de Toulouse; Francia Fil: Layre, Emilie. Université de Toulouse; Francia Fil: Vérollet, Christel. Centre National de la Recherche Scientifique; Francia. Université de Toulouse; Francia Fil: Maridonneau Parini, Isabelle. Centre National de la Recherche Scientifique; Francia. Université de Toulouse; Francia Fil: Neyrolles, Olivier. Centre National de la Recherche Scientifique; Francia. Université de Toulouse; Francia Fil: Sasiain, María del Carmen. Centre National de la Recherche Scientifique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina Fil: Lugo Villarino, Geanncarlo. Centre National de la Recherche Scientifique; Francia. Université de Toulouse; Francia Fil: Balboa, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina. Centre National de la Recherche Scientifique; Francia

The lungs harbor multiple resident microbial communities, otherwise known as the microbiota. There is an emerging interest in deciphering whether the pulmonary microbiota modulate local immunity, and whether this knowledge could shed light on mechanisms operating in the response to respiratory pathogens. In this study, we investigate the capacity of a pulmonary

The escape of cancer cells from host immunosurveillance involves a shift in immune responses, including an imbalance in Th1 and Th2 cells. A Th1-dominated immune response predicts positive outcomes in colorectal cancer. The E3 ubiquitin ligase, Asb2α, is expressed in Th2 cells, but its roles in T-cell maturation and cancer are unclear. We provide evidence that the Th2 master regulator, Gata3, induces Asb2. Loss of Asb2 did not affect Th differentiation ex vivo, but reduced IL4 production from Th2 cells. We found that high ASB2 expression was associated with poor outcome in colorectal cancer. Loss of Asb2 from hematopoietic cells promoted a Th1 response and attenuated colitis-associated tumorigenesis in mice. Diminished Th2 function correlated with increased IFNγ production and an enhanced type 1 antitumor immune response in Asb2-deficient mice. Our work suggests that Asb2α promotes a Th2 phenotype in vivo, which in turn is associated with tumor progression in a mouse model of colitis.

Rationale: Heart development involves differentiation of cardiac progenitors and assembly of the contractile sarcomere apparatus of cardiomyocytes. However, little is known about the mechanisms that regulate actin cytoskeleton remodeling during cardiac cell differentiation. Objective: The Asb2α (Ankyrin repeat-containing protein with a suppressor of cytokine signaling box 2) CRL5 (cullin 5 RING E3 ubiquitin ligase) triggers polyubiquitylation and subsequent degradation by the proteasome of FLNs (filamins). Here, we investigate the role of Asb2α in heart development and its mechanisms of action. Methods and Results: Using Asb2 knockout embryos, we show that Asb2 is an essential gene, critical to heart morphogenesis and function, although its loss does not interfere with the overall patterning of the embryonic heart tube. We show that the Asb2α E3 ubiquitin ligase controls Flna stability in immature cardiomyocytes. Importantly, Asb2α-mediated degradation of the actin-binding protein Flna marks a previously unrecognized intermediate step in cardiac cell differentiation characterized by cell shape changes and actin cytoskeleton remodeling. We further establish that in the absence of Asb2α, myofibrils are disorganized and that heartbeats are inefficient, leading to embryonic lethality in mice. Conclusions: These findings identify Asb2α as an unsuspected key regulator of cardiac cell differentiation and shed light on the molecular and cellular mechanisms determining the onset of myocardial cell architecture and its link with early cardiac function. Although Flna is known to play roles in cytoskeleton organization and to be required for heart function, this study now reveals that its degradation mediated by Asb2α ensures essential functions in differentiating cardiac progenitors.

International audience; Ubiquitin-mediated protein degradation is the main mechanism for controlled proteolysis, which is crucial for muscle development and maintenance. The ankyrin repeat-containing protein with a suppressor of cytokine signaling box 2 gene (ASB2) encodes the specificity subunit of an E3 ubiquitin ligase complex involved in differentiation of hematopoietic cells. Here, we provide the first evidence that a novel ASB2 isoform, ASB2beta, is important for muscle differentiation. ASB2beta is expressed in muscle cells during embryogenesis and in adult tissues. ASB2beta is part of an active E3 ubiquitin ligase complex and targets the actin-binding protein filamin B (FLNb) for proteasomal degradation. Thus, ASB2beta regulates FLNb functions by controlling its degradation. Knockdown of endogenous ASB2beta by shRNAs during induced differentiation of C2C12 cells delayed FLNb degradation as well as myoblast fusion and expression of muscle contractile proteins. Finally, knockdown of FLNb in ASB2beta knockdown cells restores myogenic differentiation. Altogether, our results suggest that ASB2beta is involved in muscle differentiation through the targeting of FLNb to destruction by the proteasome.

International audience; The actin-binding protein filamins (FLNs) are major organizers of the actin cytoskeleton. They control the elasticity and stiffness of the actin network and provide connections with the extracellular microenvironment by anchoring transmembrane receptors to the actin filaments. Although numerous studies have revealed the importance of FLN levels, relatively little is known about the regulation of its stability in physiological relevant settings. Here, we show that the ASB2α cullin 5-ring E3 ubiquitin ligase is highly expressed in immature dendritic cells (DCs) and is down-regulated after DC maturation. We further demonstrate that FLNs are substrates of ASB2α in immature DCs and therefore are not stably expressed in these cells, whereas they exhibit high levels of expression in mature DCs. Using ASB2 conditional knockout mice, we show that ASB2α is a critical regulator of cell spreading and podosome rosette formation in immature DCs. Furthermore, we show that ASB2(-/-) immature DCs exhibit reduced matrix-degrading function leading to defective migration. Altogether, our results point to ASB2α and FLNs as newcomers in DC biology.