The helicase-like transcription factor redirects the autophagic flux and restricts human T cell leukemia virus type 1 infection.

Retroviruses and their host have coevolved in a delicate balance between viral replication and survival of the infected cell. In this equilibrium, restriction factors expressed by infected cells control different steps of retroviral replication such as entry, uncoating, nuclear import, expression, or budding. Here, we describe a mechanism of restriction against human T cell leukemia virus type 1 (HTLV-1) by the helicase-like transcription factor (HLTF). We show that RNA and protein levels of HLTF are reduced in primary T cells of HTLV-1-infected subjects, suggesting a clinical relevance. We further demonstrate that the viral oncogene Tax represses HLTF transcription via the Enhancer of zeste homolog 2 methyltransferase of the Polycomb repressive complex 2. The Tax protein also directly interacts with HLTF and induces its proteasomal degradation. RNA interference and gene transduction in HTLV-1-infected T cells derived from patients indicate that HLTF is a restriction factor. Restoring the normal levels of HLTF expression induces the dispersal of the Golgi apparatus and overproduction of secretory granules. By synergizing with Tax-mediated NF-κB activation, physiologically relevant levels of HLTF intensify the autophagic flux. Increased vesicular trafficking leads to an enlargement of the lysosomes and the production of large vacuoles containing viral particles. HLTF induction in HTLV-1-infected cells significantly increases the percentage of defective virions. In conclusion, HLTF-mediated activation of the autophagic flux blunts the infectious replication cycle of HTLV-1, revealing an original mode of viral restriction.

Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy.

Branched-chain amino acids (BCAA) are essential amino acids playing crucial roles in protein synthesis and brain neurotransmission. Branched-chain ketoacid dehydrogenase (BCKDH), the flux-generating step of BCAA catabolism, is tightly regulated by reversible phosphorylation of its E1α-subunit. BCKDK is the kinase responsible for the phosphorylation-mediated inactivation of BCKDH. In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK. Plasma and cerebrospinal fluid concentrations of BCAA were markedly reduced. Hyperactivity of BCKDH and over-consumption of BCAA were demonstrated by functional tests in cells transfected with the mutant BCKDK. Treatment with pharmacological doses of BCAA allowed the restoring of BCAA concentrations and greatly improved seizure control. Behavioral and developmental skills of the patients improved to a lesser extent. Importantly, a retrospective review of the newborn screening results allowed the identification of a strong decrease in BCAA concentrations on dried blood spots, suggesting that BCKDK is a new treatable metabolic disorder probably amenable to newborn screening programs.

Development of ICT01, a first-in-class, anti-BTN3A antibody for activating Vγ9Vδ2 T cell-mediated antitumor immune response.

Gamma delta T (γδ T) cells are among the most potent cytotoxic lymphocytes. Activating anti­butyrophilin 3A (BTN3A) antibodies prime diverse tumor cell types to be killed by Vγ9Vδ2 T cells, the predominant γδ T cell subset in peripheral circulation, by mechanisms independent of tumor antigen­major histocompatibility complex (MHC) complexes. In this report, we describe the development of a humanized monoclonal antibody, ICT01, with subnanomolar affinity for the three isoforms of BTN3A. We demonstrate that ICT01-activated Vγ9Vδ2 T cells kill multiple tumor cell lines and primary tumor cells, but not normal healthy cells, in an efficient process requiring approximately 20% target occupancy. We show that ICT01 activity is dependent on BTN3A and BTN2A but independent of the phosphoantigen (pAg)­binding B30.2 domain. ICT01 delays the growth of hematologic and solid tumor xenografts and prolongs survival of NOD/SCID/IL2rγnull (NSG) mice adoptively transferred with human Vγ9Vδ2 T cells. In single- and multiple-dose safety studies in cynomolgus macaques that received up to 100 mg/kg once weekly, ICT01 was well tolerated. With respect to pharmacodynamic endpoints, ICT01 selectively activated Vγ9Vδ2 T cells without affecting other BTN3A-expressing lymphocytes such as αß T or B cells. A first-in-human, phase 1/2a, open-label, clinical study of ICT01 was thus initiated in patients with advanced-stage solid tumors (EVICTION: NCT04243499; EudraCT: 2019-003847-31). Preliminary results show that ICT01 was well tolerated and pharmacodynamically active in the first patients. Digital pathology analysis of tumor biopsies of a patient with melanoma suggests that ICT01 may promote immune cell infiltration within the tumor microenvironment.

Dual-specificity phosphatase 3 deletion promotes obesity, non-alcoholic steatohepatitis and hepatocellular carcinoma.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic hepatic pathology in Western countries. It encompasses a spectrum of conditions ranging from simple steatosis to more severe and progressive non-alcoholic steatohepatitis (NASH) that can lead to hepatocellular carcinoma (HCC). Obesity and related metabolic syndrome are important risk factors for the development of NAFLD, NASH and HCC. DUSP3 is a small dual-specificity protein phosphatase with a poorly known physiological function. We investigated its role in metabolic syndrome manifestations and in HCC using a mouse knockout (KO) model. While aging, DUSP3-KO mice became obese, exhibited insulin resistance, NAFLD and associated liver damage. These phenotypes were exacerbated under high fat diet (HFD). In addition, DEN administration combined to HFD led to rapid HCC development in DUSP3-KO compared to wild type (WT) mice. DUSP3-KO mice had more serum triglycerides, cholesterol, AST and ALT compared to control WT mice under both regular chow diet (CD) and HFD. The level of fasting insulin was higher compared to WT mice, though, fasting glucose as well as glucose tolerance were normal. At the molecular level, HFD led to decreased expression of DUSP3 in WT mice. DUSP3 deletion was associated with increased and consistent phosphorylation of the insulin receptor (IR) and with higher activation of the downstream signaling pathway. In conclusion, our results support a new role for DUSP3 in obesity, insulin resistance, NAFLD and liver damage.

Metastatic colorectal cancer cells maintain the TGFß program and use TGFBI to fuel angiogenesis.

Colorectal cancer (CRC) cells are traditionally considered unresponsive to TGFß due to mutations in the receptors and/or downstream signaling molecules. TGFß influences CRC cells only indirectly via stromal cells, such as cancer-associated fibroblasts. However, CRC cell ability to directly respond to TGFß currently remains unexplored. This represents a missed opportunity for diagnostic and therapeutic interventions. Methods: We examined whether cancer cells from primary CRC and liver metastases respond to TGFß by inducing TGFß-induced protein ig-h3 (TGFBI) expression, and the contribution of canonical and non-canonical TGFß signaling pathways to this effect. We then investigated in vitro and in vivo TGFBI impact on metastasis formation and angiogenesis. Using patient serum samples and an orthotopic mouse model of CRC liver metastases we assessed the diagnostic/tumor targeting value of novel antibodies against TGFBI. Results: Metastatic CRC cells, such as circulating tumor cells, directly respond to TGFß. These cells were characterized by the absence of TGFß receptor mutations and the frequent presence of p53 mutations. The pro-tumorigenic program orchestrated by TGFß in CRC cells was mediated through TGFBI, the expression of which was positively regulated by non-canonical TGFß signaling cascades. TGFBI inhibition was sufficient to significantly reduce liver metastasis formation in vivo. Moreover, TGFBI pro-tumorigenic function was linked to its ability to stimulate angiogenesis. TGFBI levels were higher in serum samples from untreated patients with CRC than in patients who were receiving chemotherapy. A radiolabeled anti-TGFBI antibody selectively targeted metastatic lesions in vivo, underscoring its diagnostic and therapeutic potential. Conclusions: TGFß signaling in CRC cells directly contributes to their metastatic potential and stromal cell-independence. Proteins downstream of activated TGFß, such as TGFBI, represent novel diagnostic and therapeutic targets for more specific anti-metastatic therapies.

MKP1 phosphatase is recruited by CXCL12 in glioblastoma cells and plays a role in DNA strand breaks repair.

Glioblastoma (GBM) is the most frequent and aggressive primary tumor in the central nervous system. Previously, the secretion of CXCL12 in the brain subventricular zones has been shown to attract GBM cells and protect against irradiation. However, the exact molecular mechanism behind this radioprotection is still unknown. Here, we demonstrate that CXCL12 modulates the phosphorylation of MAP kinases and their regulator, the nuclear MAP kinase phosphatase 1 (MKP1). We further show that MKP1 is able to decrease GBM cell death and promote DNA repair after irradiation by regulating major apoptotic players, such as Jun-N-terminal kinase, and by stabilizing the DNA repair protein RAD51. Increases in MKP1 levels caused by different corticoid treatments should be reexamined for GBM patients, particularly during their radiotherapy sessions, in order to prevent or to delay the relapses of this tumor.

Myoferlin Contributes to the Metastatic Phenotype of Pancreatic Cancer Cells by Enhancing Their Migratory Capacity through the Control of Oxidative Phosphorylation.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies with an overall survival of 5% and is the second cause of death by cancer, mainly linked to its high metastatic aggressiveness. Accordingly, understanding the mechanisms sustaining the PDAC metastatic phenotype remains a priority. In this study, we generated and used a murine in vivo model to select clones from the human Panc-1 PDAC cell line that exhibit a high propensity to seed and metastasize into the liver. We showed that myoferlin, a protein previously reported to be overexpressed in PDAC, is significantly involved in the migratory abilities of the selected cells. We first report that highly metastatic Panc-1 clones expressed a significantly higher myoferlin level than the corresponding low metastatic ones. Using scratch wound and Boyden's chamber assays, we show that cells expressing a high myoferlin level have higher migratory potential than cells characterized by a low myoferlin abundance. Moreover, we demonstrate that myoferlin silencing leads to a migration decrease associated with a reduction of mitochondrial respiration. Since mitochondrial oxidative phosphorylation has been shown to be implicated in the tumor progression and dissemination, our data identify myoferlin as a valid potential therapeutic target in PDAC.

Melanoma antigen-D2 controls cell cycle progression and modulates the DNA damage response.

Overexpression of the ubiquitous type II melanoma antigen-D2 (MAGED2) in numerous types of cancer suggests that this protein contributes to carcinogenesis, a well-documented characteristic of other MAGE proteins. Modification of MAGED2 intracellular localization during cell cycle phases and following treatment with camptothecin (CPT) and phosphorylation by ATM/ATR following ionizing irradiation led us to investigate the molecular functions of MAGED2 in the cellular response to DNA damage. Cell cycle regulators, cell cycle progression, and bromodeoxyuridine (BrdU) incorporation were compared between MAGED2-sufficient and -depleted U2OS cells following exposure to CPT. At 24 h post-CPT removal, MAGED2-depleted cells had lower levels of p21 and p27, and there was an increase in S phase BrdU-positive cells with a concurrent decrease in cells in G2. These cell cycle modifications were p21-independent, but ATR-, SKP2-, and CDC20-dependent. Importantly, while MAGED2 depletion reduced CHK2 phosphorylation after 8 h of CPT treatment, it enhanced and prolonged CHK1 phosphorylation after a 24 h recovery period, indicating sustained ATR activation. MAGED2 depletion had no impact on cell survival under our experimental conditions. In summary, our data indicate that MAGED2 reduced CPT-related replicative stress, suggesting a role for this protein in genomic stability.

RIP3 antagonizes a TSC2-mediated pro-survival pathway in glioblastoma cell death.

Glioblastomas are the deadliest type of brain cancer and are frequently associated with poor prognosis and a high degree of recurrence despite removal by surgical resection and treatment by chemo- and radio-therapy. Photodynamic therapy (PDT) is a treatment well known to induce mainly necrotic and apoptotic cell death in solid tumors. 5-Aminolevulinic acid (5-ALA)-based PDT was recently shown to sensitize human glioblastoma cells (LN-18) to a RIP3 (Receptor Interacting Protein 3)-dependent cell death which is counter-acted by activation of autophagy. These promising results led us to investigate the pathways involved in cell death and survival mechanisms occurring in glioblastoma following PDT. In the present study, we describe a new TSC2 (Tuberous Sclerosis 2)-dependent survival pathway implicating MK2 (MAPKAPK2) kinase and 14-3-3 proteins which conducts to the activation of a pro-survival autophagy. Moreover, we characterized a new RIP3/TSC2 complex where RIP3 is suggested to promote cell death by targeting TSC2-dependent survival pathway. These results highlight (i) a new role of TSC2 to protect glioblastoma against PDT-induced cell death and (ii) TSC2 and 14-3-3 as new RIP3 partners.

CXCL12 mediates glioblastoma resistance to radiotherapy in the subventricular zone.

BACKGROUND: Patients with glioblastoma (GBM) have an overall median survival of 15 months despite multimodal therapy. These catastrophic survival rates are to be correlated to systematic relapses that might arise from remaining glioblastoma stem cells (GSCs) left behind after surgery. In this line, it has recently been demonstrated that GSCs are able to escape the tumor mass and preferentially colonize the adult subventricular zone (SVZ). At a distance from the initial tumor site, these GSCs might therefore represent a high-quality model of clinical resilience to therapy and cancer relapses as they specifically retain tumor-initiating abilities. METHOD: While relying on recent findings that have validated the existence of GSCs in the human SVZ, we questioned the role of the SVZ niche as a potential GSC reservoir involved in therapeutic failure. RESULTS: Our results demonstrate that (i) GSCs located in the SVZ are specifically resistant to radiation in vivo, (ii) these cells display enhanced mesenchymal roots that are known to be associated with cancer radioresistance, (iii) these mesenchymal traits are specifically upregulated by CXCL12 (stromal cell-derived factor-1) both in vitro and in the SVZ environment, (iv) the amount of SVZ-released CXCL12 mediates GBM resistance to radiation in vitro, and (v) interferes with the CXCL12/CXCR4 signalling system, allowing weakening of the tumor mesenchymal roots and radiosensitizing SVZ-nested GBM cells. CONCLUSION: Together, these data provide evidence on how the adult SVZ environment, through the release of CXCL12, supports GBM therapeutic failure and potential tumor relapse.

Melanoma antigen-D2: A nucleolar protein undergoing delocalization during cell cycle and after cellular stress.

Melanoma antigen D2 (MAGE-D2) is recognized as a cancer diagnostic marker; however, it has poorly characterized functions. Here, we established its intracellular localization and shuttling during cell cycle progression and in response to cellular stress. In normal conditions, MAGE-D2 is present in the cytoplasm, nucleoplasm, and nucleoli. Within the latter, MAGE-D2 is mostly found in the granular and the dense fibrillar components, and it interacts with nucleolin. Transfection of MAGE-D2 deletion mutants demonstrated that Δ203-254 leads to confinement of MAGE-D2 to the cytoplasm, while Δ248-254 prevents its accumulation in nucleoli but still allows its presence in the nucleoplasm. Consequently, this short sequence belongs to a nucleolar localization signal. MAGE-D2 deletion does not alter the nucleolar organization or rRNA levels. However, its intracellular localization varies with the cell cycle in a different kinetic than nucleolin. After genotoxic and nucleolar stresses, MAGE-D2 is excluded from nucleoli and concentrates in the nucleoplasm. We demonstrated that its camptothecin-related delocalization results from two distinct events: a rapid nucleolar release and a slower phospho-ERK-dependent cytoplasm to nucleoplasm translocation, which results from an increased flux from the cytoplasm to nucleoplasm. In conclusion, MAGE-D2 is a dynamic protein whose shuttling properties could suggest a role in cell cycle regulation.

Asporin Is a Fibroblast-Derived TGF-ß1 Inhibitor and a Tumor Suppressor Associated with Good Prognosis in Breast Cancer.

BACKGROUND: Breast cancer is a leading malignancy affecting the female population worldwide. Most morbidity is caused by metastases that remain incurable to date. TGF-ß1 has been identified as a key driving force behind metastatic breast cancer, with promising therapeutic implications. METHODS AND FINDINGS: Employing immunohistochemistry (IHC) analysis, we report, to our knowledge for the first time, that asporin is overexpressed in the stroma of most human breast cancers and is not expressed in normal breast tissue. In vitro, asporin is secreted by breast fibroblasts upon exposure to conditioned medium from some but not all human breast cancer cells. While hormone receptor (HR) positive cells cause strong asporin expression, triple-negative breast cancer (TNBC) cells suppress it. Further, our findings show that soluble IL-1ß, secreted by TNBC cells, is responsible for inhibiting asporin in normal and cancer-associated fibroblasts. Using recombinant protein, as well as a synthetic peptide fragment, we demonstrate the ability of asporin to inhibit TGF-ß1-mediated SMAD2 phosphorylation, epithelial to mesenchymal transition, and stemness in breast cancer cells. In two in vivo murine models of TNBC, we observed that tumors expressing asporin exhibit significantly reduced growth (2-fold; p = 0.01) and metastatic properties (3-fold; p = 0.045). A retrospective IHC study performed on human breast carcinoma (n = 180) demonstrates that asporin expression is lowest in TNBC and HER2+ tumors, while HR+ tumors have significantly higher asporin expression (4-fold; p = 0.001). Assessment of asporin expression and patient outcome (n = 60; 10-y follow-up) shows that low protein levels in the primary breast lesion significantly delineate patients with bad outcome regardless of the tumor HR status (area under the curve = 0.87; 95% CI 0.78-0.96; p = 0.0001). Survival analysis, based on gene expression (n = 375; 25-y follow-up), confirmed that low asporin levels are associated with a reduced likelihood of survival (hazard ratio = 0.58; 95% CI 0.37-0.91; p = 0.017). Although these data highlight the potential of asporin to serve as a prognostic marker, confirmation of the clinical value would require a prospective study on a much larger patient cohort. CONCLUSIONS: Our data show that asporin is a stroma-derived inhibitor of TGF-ß1 and a tumor suppressor in breast cancer. High asporin expression is significantly associated with less aggressive tumors, stratifying patients according to the clinical outcome. Future pre-clinical studies should consider options for increasing asporin expression in TNBC as a promising strategy for targeted therapy.

Adult mouse subventricular zones stimulate glioblastoma stem cells specific invasion through CXCL12/CXCR4 signaling.

BACKGROUND: Patients with glioblastoma multiforme (GBM) have an overall median survival of 15 months. This catastrophic survival rate is the consequence of systematic relapses that could arise from remaining glioblastoma stem cells (GSCs) left behind after surgery. We previously demonstrated that GSCs are able to escape the tumor mass and specifically colonize the adult subventricular zones (SVZs) after transplantation. This specific localization, away from the initial injection site, therefore represents a high-quality model of a clinical obstacle to therapy and relapses because GSCs notably retain the ability to form secondary tumors. METHOD: In this work, we questioned the role of the CXCL12/CXCR4 signaling in the GSC-specific invasion of the SVZs. RESULTS: We demonstrated that both receptor and ligand are respectively expressed by different GBM cell populations and by the SVZ itself. In vitro migration bio-assays highlighted that human U87MG GSCs isolated from the SVZs (U87MG-SVZ) display stronger migratory abilities in response to recombinant CXCL12 and/or SVZ-conditioned medium (SVZ-CM) compared with cancer cells isolated from the tumor mass (U87MG-TM). Moreover, in vitro inhibition of the CXCR4 signaling significantly decreased the U87MG-SVZ cell migration in response to the SVZ-CM. Very interestingly, treating U87MG-xenografted mice with daily doses of AMD3100, a specific CXCR4 antagonist, prevented the specific invasion of the SVZ. Another in vivo experiment, using CXCR4-invalidated GBM cells, displayed similar results. CONCLUSION: Taken together, these data demonstrate the significant role of the CXCL12/CXCR4 signaling in this original model of brain cancer invasion.

Varicella-zoster virus induces the formation of dynamic nuclear capsid aggregates.

The first step of herpesviruses virion assembly occurs in the nucleus. However, the exact site where nucleocapsids are assembled, where the genome and the inner tegument are acquired, remains controversial. We created a recombinant VZV expressing ORF23 (homologous to HSV-1 VP26) fused to the eGFP and dually fluorescent viruses with a tegument protein additionally fused to a red tag (ORF9, ORF21 and ORF22 corresponding to HSV-1 UL49, UL37 and UL36). We identified nuclear dense structures containing the major capsid protein, the scaffold protein and maturing protease, as well as ORF21 and ORF22. Correlative microscopy demonstrated that the structures correspond to capsid aggregates and time-lapse video imaging showed that they appear prior to the accumulation of cytoplasmic capsids, presumably undergoing the secondary egress, and are highly dynamic. Our observations suggest that these structures might represent a nuclear area important for capsid assembly and/or maturation before the budding at the inner nuclear membrane.

Organized proteomic heterogeneity in colorectal cancer liver metastases and implications for therapies.

UNLABELLED: Tumor heterogeneity is a major obstacle for developing effective anticancer treatments. Recent studies have pointed to large stochastic genetic heterogeneity within cancer lesions, where no pattern seems to exist that would enable a more structured targeted therapy approach. Because to date no similar information is available at the protein (phenotype) level, we employed matrix assisted laser desorption ionization (MALDI) image-guided proteomics and explored the heterogeneity of extracellular and membrane subproteome in a unique collection of eight fresh human colorectal carcinoma (CRC) liver metastases. Monitoring the spatial distribution of over 1,000 proteins, we found unexpectedly that all liver metastasis lesions displayed a reproducible, zonally delineated pattern of functional and therapeutic biomarker heterogeneity. The peritumoral region featured elevated lipid metabolism and protein synthesis, the rim of the metastasis displayed increased cellular growth, movement, and drug metabolism, whereas the center of the lesion was characterized by elevated carbohydrate metabolism and DNA-repair activity. From the aspect of therapeutic targeting, zonal expression of known and novel biomarkers was evident, reinforcing the need to select several targets in order to achieve optimal coverage of the lesion. Finally, we highlight two novel antigens, LTBP2 and TGFBI, whose expression is a consistent feature of CRC liver metastasis. We demonstrate their in vivo antibody-based targeting and highlight their potential usefulness for clinical applications. CONCLUSION: The proteome heterogeneity of human CRC liver metastases has a distinct, organized pattern. This particular hallmark can now be used as part of the strategy for developing rational therapies based on multiple sets of targetable antigens.

Association of biomarkers of lipid modification with functional and morphological indices of coronary stenosis severity in stable coronary artery disease.

Biomarkers of blood lipid modification and oxidative stress have been associated with increased cardiovascular morbidity. We sought to determine whether these biomarkers were related to functional indices of stenosis severity among patients with stable coronary artery disease. We studied 197 consecutive patients with stable coronary artery disease due to single vessel disease. Fractional flow reserve (FFR) ≤ 0.80 was assessed as index of a functionally significant lesion. Serum levels of secretory phospholipase A2 (sPLA2) activity, secretory phospholipase A2 type IIA (sPLA2-IIA), myeloperoxydase (MPO), lipoprotein-associated phospholipase A2 (Lp-PLA2), and oxidized low-density lipoprotein (OxLDL) were assessed using commercially available assays. Patients with FFR > 0.8 had higher sPLA2 activity, sPLA2 IIA, and OxLDL levels than patients with FFR ≤ 0.8 (21.25 [16.03-27.28] vs 25.85 [20.58-34.63] U/mL, p < 0.001, 2.0 [1.5-3.4] vs 2.6 [2.0-3.4] ng/mL, p < 0.01; and 53.0 [36.0-71.0] vs 64.5 [50-89.25], p < 0.001 respectively). Patients with FFR > 0.80 had similar Lp-PLA2 and MPO levels versus those with FFR ≤ 0.8. sPLA2 activity, sPLA2 IIA significantly increased area under the curve over baseline characteristics to predict FFR ≤ 0.8 (0.67 to 0.77 (95 % confidence interval [CI]: 0.69-0.85) p < 0.01 and 0.67 to 0.77 (95 % CI: 0.69-0.84) p < 0.01, respectively). Serum sPLA2 activity as well as sPLA2-IIA level is related to functional characteristics of coronary stenoses in patients with stable coronary artery disease.

Spatiotemporal autophagic degradation of oxidatively damaged organelles after photodynamic stress is amplified by mitochondrial reactive oxygen species.

Although reactive oxygen species (ROS) have been reported to evoke different autophagic pathways, how ROS or their secondary products modulate the selective clearance of oxidatively damaged organelles is less explored. To investigate the signaling role of ROS and the impact of their compartmentalization in autophagy pathways, we used murine fibrosarcoma L929 cells overexpressing different antioxidant enzymes targeted to the cytosol or mitochondria and subjected them to photodynamic (PD) stress with the endoplasmic reticulum (ER)-associated photosensitizer hypericin. We show that following apical ROS-mediated damage to the ER, predominantly cells overexpressing mitochondria-associated glutathione peroxidase 4 (GPX4) and manganese superoxide dismutase (SOD2) displayed attenuated kinetics of autophagosome formation and overall cell death, as detected by computerized time-lapse microscopy. Consistent with a primary ER photodamage, kinetics and colocalization studies revealed that photogenerated ROS induced an initial reticulophagy, followed by morphological changes in the mitochondrial network that preceded clearance of mitochondria by mitophagy. Overexpression of cytosolic and mitochondria-associated GPX4 retained the tubular mitochondrial network in response to PD stress and concomitantly blocked the progression toward mitophagy. Preventing the formation of phospholipid hydroperoxides and H(2)O(2) in the cytosol as well as in the mitochondria significantly reduced cardiolipin peroxidation and apoptosis. All together, these results show that in response to apical ER photodamage ROS propagate to mitochondria, which in turn amplify ROS production, thereby contributing to two antagonizing processes, mitophagy and apoptosis.

The inositol phosphatase SHIP-1 inhibits NOD2-induced NF-κB activation by disturbing the interaction of XIAP with RIP2.

SHIP-1 is an inositol phosphatase predominantly expressed in hematopoietic cells. Over the ten past years, SHIP-1 has been described as an important regulator of immune functions. Here, we characterize a new inhibitory function for SHIP-1 in NOD2 signaling. NOD2 is a crucial cytoplasmic bacterial sensor that activates proinflammatory and antimicrobial responses upon bacterial invasion. We observed that SHIP-1 decreases NOD2-induced NF-κB activation in macrophages. This negative regulation relies on its interaction with XIAP. Indeed, we observed that XIAP is an essential mediator of the NOD2 signaling pathway that enables proper NF-κB activation in macrophages. Upon NOD2 activation, SHIP-1 C-terminal proline rich domain (PRD) interacts with XIAP, thereby disturbing the interaction between XIAP and RIP2 in order to decrease NF-κB signaling.

The c-Jun N-terminal kinase (JNK)-binding protein (JNKBP1) acts as a negative regulator of NOD2 protein signaling by inhibiting its oligomerization process.

NOD2 is one of the best characterized members of the cytosolic NOD-like receptor family. NOD2 is able to sense muramyl dipeptide, a specific bacterial cell wall component, and to subsequently induce various signaling pathways leading to NF-κB activation and autophagy, both events contributing to an efficient innate and adaptive immune response. Interestingly, loss-of-function NOD2 variants were associated with a higher susceptibility for Crohn disease, which highlights the physiological importance of proper regulation of NOD2 activity. We performed a biochemical screen to search for new NOD2 regulators. We identified a new NOD2 partner, c-Jun N-terminal kinase-binding protein 1 (JNKBP1), a scaffold protein characterized by an N-terminal WD-40 domain. JNKBP1, through its WD-40 domain, binds to NOD2 following muramyl dipeptide activation. This interaction attenuates NOD2-mediated NF-κB activation and IL-8 secretion as well as NOD2 antibacterial activity. JNKBP1 exerts its repressor effect by disturbing NOD2 oligomerization and RIP2 tyrosine phosphorylation, both steps required for downstream NOD2 signaling. We furthermore showed that JNKBP1 and NOD2 are co-expressed in the human intestinal epithelium and in immune cells recruited in the lamina propria, which suggests that JNKBP1 contributes to maintain NOD2-mediated intestinal immune homeostasis.