Histone chaperone HIRA, Promyelocytic Leukemia (PML) protein and p62/SQSTM1 coordinate to regulate inflammation during cell senescence.

Cellular senescence, a stress-induced stable proliferation arrest associated with an inflammatory Senescence-Associated Secretory Phenotype (SASP), is a cause of aging. In senescent cells, Cytoplasmic Chromatin Fragments (CCFs) activate SASP via the anti-viral cGAS/STING pathway. PML protein organizes PML nuclear bodies (NBs), also involved in senescence and anti-viral immunity. The HIRA histone H3.3 chaperone localizes to PML NBs in senescent cells. Here, we show that HIRA and PML are essential for SASP expression, tightly linked to HIRA's localization to PML NBs. Inactivation of HIRA does not directly block expression of NF-κB target genes. Instead, an H3.3-independent HIRA function activates SASP through a CCF-cGAS-STING-TBK1-NF-κB pathway. HIRA physically interacts with p62/SQSTM1, an autophagy regulator and negative SASP regulator. HIRA and p62 co-localize in PML NBs, linked to their antagonistic regulation of SASP, with PML NBs controlling their spatial configuration. These results outline a role for HIRA and PML in regulation of SASP.

A BioID-Derived Proximity Interactome for SARS-CoV-2 Proteins.

The novel coronavirus SARS-CoV-2 is responsible for the ongoing COVID-19 pandemic and has caused a major health and economic burden worldwide. Understanding how SARS-CoV-2 viral proteins behave in host cells can reveal underlying mechanisms of pathogenesis and assist in development of antiviral therapies. Here, the cellular impact of expressing SARS-CoV-2 viral proteins was studied by global proteomic analysis, and proximity biotinylation (BioID) was used to map the SARS-CoV-2 virus-host interactome in human lung cancer-derived cells. Functional enrichment analyses revealed previously reported and unreported cellular pathways that are associated with SARS-CoV-2 proteins. We have established a website to host the proteomic data to allow for public access and continued analysis of host-viral protein associations and whole-cell proteomes of cells expressing the viral-BioID fusion proteins. Furthermore, we identified 66 high-confidence interactions by comparing this study with previous reports, providing a strong foundation for future follow-up studies. Finally, we cross-referenced candidate interactors with the CLUE drug library to identify potential therapeutics for drug-repurposing efforts. Collectively, these studies provide a valuable resource to uncover novel SARS-CoV-2 biology and inform development of antivirals.

A BioID-derived proximity interactome for SARS-CoV-2 proteins.

The novel coronavirus SARS-CoV-2 is responsible for the ongoing COVID-19 pandemic and has caused a major health and economic burden worldwide. Understanding how SARS-CoV-2 viral proteins behave in host cells can reveal underlying mechanisms of pathogenesis and assist in development of antiviral therapies. Here we use BioID to map the SARS-CoV-2 virus-host interactome using human lung cancer derived A549 cells expressing individual SARS-CoV-2 viral proteins. Functional enrichment analyses revealed previously reported and unreported cellular pathways that are in association with SARS-CoV-2 proteins. We have also established a website to host the proteomic data to allow for public access and continued analysis of host-viral protein associations and whole-cell proteomes of cells expressing the viral-BioID fusion proteins. Collectively, these studies provide a valuable resource to potentially uncover novel SARS-CoV-2 biology and inform development of antivirals.

Reduction of sulfenic acids by ascorbate in proteins, connecting thiol-dependent to alternative redox pathways.

Sulfenic acids are the primary product of thiol oxidation by hydrogen peroxide and other oxidants. Several aspects of sulfenic acid formation through thiol oxidation were established recently. In contrast, the reduction of sulfenic acids is still scarcely investigated. Here, we characterized the kinetics of the reduction of sulfenic acids by ascorbate in several proteins. Initially, we described the crystal structure of our model protein (Tsa2-C170S). There are other Tsa2 structures in distinct redox states in public databases and all of them are decamers, with the peroxidatic cysteine very accessible to reductants, convenient features to investigate kinetics. We determined that the reaction between Tsa2-C170S-Cys-SOH and ascorbate proceeded with a rate constant of 1.40 ± 0.08 × 103 M-1 s-1 through a competition assay developed here, employing 2,6-dichlorophenol-indophenol (DCPIP). A series of peroxiredoxin enzymes (Prx6 sub family) were also analyzed by this competition assay and we observed that the reduction of sulfenic acids by ascorbate was in the 0.4-2.2 × 103 M-1 s-1 range. We also evaluated the same reaction on glyceraldehyde 3-phosphate dehydrogenase and papain, as the reduction of their sulfenic acids by ascorbate were reported previously. Once again, the rate constants are in the 0.4-2.2 × 103 M-1 s-1 range. We also analyzed the reduction of Tsa2-C170S-SOH by ascorbate by a second, independent method, following hydrogen peroxide reduction through a specific electrode (ISO-HPO-2, World Precision Instruments) and employing a bi-substrate, steady state approach. The kcat/KMAsc was 7.4 ± 0.07 × 103 M-1 s-1, which was in the same order of magnitude as the value obtained by the DCPIP competition assay. In conclusion, our data indicates that reduction of sulfenic acid in various proteins proceed at moderate rate and probably this reaction is more relevant in biological systems where ascorbate concentrations are high.

Fibrinogen Gamma Chain Promotes Aggregation of Vesicular Stomatitis Virus in Saliva.

The spread of viruses among cells and hosts often involves multi-virion structures. For instance, virions can form aggregates that allow for the co-delivery of multiple genome copies to the same cell from a single infectious unit. Previously, we showed that vesicular stomatitis virus (VSV), an enveloped, negative-strand RNA virus, undergoes strong aggregation in the presence of saliva from certain individuals. However, the molecular components responsible for such aggregation remain unknown. Here we show that saliva-driven aggregation is protein dependent, and we use comparative proteomics to analyze the protein content of strongly versus poorly aggregating saliva. Quantitative analysis of over 300 proteins led to the identification of 18 upregulated proteins in strongly aggregating saliva. One of these proteins, the fibrinogen gamma chain, was verified experimentally as a factor promoting VSV aggregation in a dose-dependent manner. This study hence identifies a protein responsible for saliva-driven VSV aggregation. Yet, the possible involvement of additional proteins or factors cannot be discarded.

NOD-like receptors: major players (and targets) in the interface between innate immunity and cancer.

Innate immunity comprises several inflammation-related modulatory pathways which receive signals from an array of membrane-bound and cytoplasmic pattern recognition receptors (PRRs). The NLRs (NACHT (NAIP (neuronal apoptosis inhibitor protein), C2TA (MHC class 2 transcription activator), HET-E (incompatibility locus protein from Podospora anserina) and TP1 (telomerase-associated protein) and Leucine-Rich Repeat (LRR) domain containing proteins) relate to a large family of cytosolic innate receptors, involved in detection of intracellular pathogens and endogenous byproducts of tissue injury. These receptors may recognize pathogen-associated molecular patterns (PAMPs) and/or danger-associated molecular patterns (DAMPs), activating host responses against pathogen infection and cellular stress. NLR-driven downstream signals trigger a number of signaling circuitries, which may either initiate the formation of inflammasomes and/or activate nuclear factor κB (NF-κB), stress kinases, interferon response factors (IRFs), inflammatory caspases and autophagy. Disruption of those signals may lead to a number of pro-inflammatory conditions, eventually promoting the onset of human malignancies. In this review, we describe the structures and functions of the most well-defined NLR proteins and highlight their association and biological impact on a diverse number of cancers.

The crossroads of breast cancer progression: insights into the modulation of major signaling pathways.

Cancer is the disease with highest public health impact in developed countries. Particularly, breast cancer has the highest incidence in women worldwide and the fifth highest mortality in the globe, imposing a significant social and economic burden to society. The disease has a complex heterogeneous etiology, being associated with several risk factors that range from lifestyle to age and family history. Breast cancer is usually classified according to the site of tumor occurrence and gene expression profiling. Although mutations in a few key genes, such as BRCA1 and BRCA2, are associated with high breast cancer risk, the large majority of breast cancer cases are related to mutated genes of low penetrance, which are frequently altered in the whole population. Therefore, understanding the molecular basis of breast cancer, including the several deregulated genes and related pathways linked to this pathology, is essential to ensure advances in early tumor detection and prevention. In this review, we outline key cellular pathways whose deregulation has been associated with breast cancer, leading to alterations in cell proliferation, apoptosis, and the delicate hormonal balance of breast tissue cells. Therefore, here we describe some potential breast cancer-related nodes and signaling concepts linked to the disease, which can be positively translated into novel therapeutic approaches and predictive biomarkers.

Dissecting Major Signaling Pathways throughout the Development of Prostate Cancer.

Prostate cancer (PCa) is one of the most common malignancies found in males. The development of PCa involves several mutations in prostate epithelial cells, usually linked to developmental changes, such as enhanced resistance to apoptotic death, constitutive proliferation, and, in some cases, to differentiation into an androgen deprivation-resistant phenotype, leading to the appearance of castration-resistant PCa (CRPCa), which leads to a poor prognosis in patients. In this review, we summarize recent findings concerning the main deregulations into signaling pathways that will lead to the development of PCa and/or CRPCa. Key mutations in some pathway molecules are often linked to a higher prevalence of PCa, by directly affecting the respective cascade and, in some cases, by deregulating a cross-talk node or junction along the pathways. We also discuss the possible environmental and nonenvironmental inducers for these mutations, as well as the potential therapeutic strategies targeting these signaling pathways. A better understanding of how some risk factors induce deregulation of these signaling pathways, as well as how these deregulated pathways affect the development of PCa and CRPCa, will further help in the development of new treatments and prevention strategies for this disease.

Glutathione and iron at the crossroad of redox metabolism in rats infected by Trypanosoma evansi.

The aim of this study was to evaluate the changes in hematological and biochemical parameters of blood during acute Trypanosoma evansi infection in Wistar rats. The end points studied were hematologic parameters, red blood cell fragility, iron content, and glutathione and lipid peroxidation levels. Forty-eight animals were infected with trypomastigotes and distributed into five groups according to the level of parasitemia. Twelve non-inoculated animals were used as control. Parasitemia increased progressively, reaching highest scores at 15 days post-inoculation. At this point, several deleterious effects were observed such as an increase in iron content, in osmotic fragility, and in lipid peroxidation index, while glutathione decreased drastically. These changes were highly correlated to parasitemia (p < 0.0001) and among each other (p ≤ 0.001). Hematological indices (Hb, packed cell volume (PCV), red blood cells (RBC), and mean corpuscular hemoglobin concentration) were also correlated to parasitemia (p ≤ 0.0003) but failed to correlate to the other variables. Along with increase in iron, RBC fragility produced a decrease in RBC, PCV, and Hb, but not in mean corpuscular volume. Decrease in glutathione was negatively correlated to the end products of lipid peroxidation, clearly indicating the establishment of a pro-oxidant condition. The results show that the infection causes hematological impairments, increases iron and osmotic fragility, along with marked oxidative stress in red blood cells of rats inoculated with T. evansi.