Regulated exocytosis in immune function: are SNARE-proteins involved?

Nasal Transcriptome and Epigenome Analysis Identifies the Pathogenic Features of Aspirin-Exacerbated Respiratory Disease

Dysregulation of the arachidonic acid metabolic pathway is the most widely known pathomechanism of aspirin-exacerbated respiratory disease (AERD). This study aimed to perform integrative analysis of transcriptomic and epigenomic profiling with network analysis to determine the novel pathogenic features of AERD. Ten patients with asthma including 5 patients with AERD and another 5 patients with aspirin tolerant asthma (ATA) were enrolled. Nasal scraping was performed and nasal mucosa was used in omics profiling. Peripheral eosinophil counts, sputum eosinophil counts, fractional exhaled nitric oxide levels, and pulmonary function test results were evaluated. Differentially expressed genes (DEGs), differentially methylated probes (DMPs) and differentially correlated genes (DCGs) between patients with AERD and those with ATA were analyzed. Network analysis using ingenuity pathway analysis (IPA) was performed to determine the gene connection network and signaling pathways. In total, 1,736 DEGs, 1,401 DMPs, and 19 pairs for DCGs were identified. Among DCGs, genes related to vesicle transport (e.g., RAB3B and STX2) and sphingolipid dysregulation (e.g., SMPD3) were found to be hypo-methylated and up-regulated in AERD. Using the canonical pathway analysis of IPA with 78 asthma-related DEGs, signaling pathways of T helper cell differentiation/activation and Fcε receptor I were generated. Up-regulation of RORγt and FcER1A were noted in AERD. Gene expression levels of RAB3B, SYNE1, STX2, SMPD3 and RORγt were significantly associated with sputum eosinophil counts. Quantitative real-time polymerase chain reaction was performed and mRNA expression levels of STX2, SMPD3, RORγt, and FcER1A were significantly higher in AERD compared to ATA. Distinct pathogenic features were identified by using integrative multi-omics data analysis in patients with AERD.

Exploring the Transcriptome Dynamics of In Vivo Theileria annulata Infection in Crossbred Cattle

The molecular changes occurring in the host in response to in vivo Theileria annulata parasitic infection are not well understood. Therefore, the present study investigated the differential expression profiles of peripheral blood mononuclear cells (PBMCs) across Theileria annulata-infected and non-infected crossbred cows. The differential expression profiles from PBMCs of infected and non-infected crossbred cows were generated by RNA sequencing. A marked difference in the expression of genes associated with innate immunity (FTH1, ACTB, ISG15) was observed between the two groups. The over-represented pathways in Theileria annulata-infected cows were associated with the immune system and regulation of the mitotic cycle. Enriched genes and pathways in non-infected animals were associated with the maintenance of chromatin integrity and cell structure. The highly connected genes identified in this study form potential candidates for further investigation into host-parasite interactions in cattle. An improved understanding of the transcriptomic dynamics during theileriosis would lead to underpinning molecular level differences related to the health status of cattle.

Calcium signaling and regulation of neutrophil functions: Still a long way to go

Neutrophils are the most abundant leukocytes in blood and disruption in their functions often results in an increased risk of serious infections and inflammatory autoimmune diseases. Following recent discoveries in their influence over disease progression, a resurgence of interest for neutrophil biology has taken place. The multitude of signaling pathways activated by the engagement of numerous types of receptors, with which neutrophils are endowed, reflects the functional complexity of these cells. It is therefore not surprising that there remains a huge lack in the understanding of molecular mechanisms underlining neutrophil functions. Moreover, studies on neutrophils are undoubtedly limited by the difficulty to efficiently edit the cell's genome. Over the past 30 years, compelling evidence has clearly highlighted that Ca²⁺ -signaling is governing the key processes associated with neutrophil functions. The confirmation of the role of an elevation of intracellular Ca²⁺ concentration has come from studies on NADPH oxidase activation and phagocytosis. In this review, we give an overview and update of our current knowledge on the role of Ca²⁺ mobilization in the regulation of pro-inflammatory functions of neutrophils. In particular, we stress the importance of Ca²⁺ in the formation of NETs and cytokine secretion in the light of newest findings. This will allow us to embrace how much further we have to go to understand the complex dynamics of Ca²⁺ -dependent mechanisms in order to gain more insights into the role of neutrophils in the pathogenesis of inflammatory diseases. The potential for therapeutics to regulate the neutrophil functions, such as Ca²⁺ influx inhibitors to prevent autoimmune and chronic inflammatory diseases, has been discussed in the last part of the review.

Increased expression levels of Syntaxin 1A and Synaptobrevin 2/Vesicle-Associated Membrane Protein-2 are associated with the progression of bladder cancer

Gene expression is tightly regulated in time and space through a multitude of factors consisting of signaling molecules. Soluble N-ethylmaleimide-sensitive-factor attachment protein receptors (SNARE) are membrane proteins responsible for the intercellular trafficking of signals through endocytosis and exocytosis of vesicles. Altered expression of SNARE proteins in cellular communication is the major hallmark of cancer phenotypes as indicated in recent studies. SNAREs play an important role in maintaining cell growth and epithelial membrane permeability of the bladder and are not only involved in cancer progression but also metastatic cell invasion through SNARE-mediated trafficking. Synaptobrevin2/Vesicle associated membrane protein-2 (v-SNARE) and Syntaxin (t-SNARE) form a vesicular docking complex during endocytosis. Some earlier studies have shown a critical role of SNARE in colon, lungs, and breast cancer progression and metastasis. In this study, we analyzed the relative expression of the STX1A and VAMP2 (SYB2) for their possible association in the progression and metastasis of bladder cancer. The profiling of the genes showed a significant increase in STX1A and VAMP2 expression (p < 0.001) in high-grade tumor cells compared to normal and low-grade tumors. These findings suggest that elevated expression of STX1A and VAMP2 might have caused the abnormal progression and invasion of cancer cells leading to the transformation of cells into high-grade tumor in bladder cancer.

Epimorphin(-/-) mice are protected, in part, from acute colitis via decreased interleukin 6 signaling

Epimorphin (Epim), a member of the syntaxin family of membrane-bound, intracellular vesicle-docking proteins, is expressed in intestinal myofibroblasts and macrophages. We demonstrated previously that Epimorphin(-/-)(Epim(-/-)) mice are protected, in part, from dextran sodium sulfate (DSS)-induced colitis. Although interleukin (IL)-6/p-Stat3 signaling has been implicated in the pathogenesis of colitis, the myofibroblast contribution to IL-6 signaling in colitis remains unexplored. Our aim was to investigate the IL-6 pathway in Epim(-/-) mice in the DSS colitis model. Whole colonic tissue, epithelium, and stroma of WT and congenic Epim(-/-) mice treated with 5% DSS for 7 days were analyzed for IL-6 and a downstream effector, p-Stat3, by immunostaining and immunoblot. Colonic myofibroblast and peritoneal macrophage IL-6 secretion were evaluated by enzyme-linked immunosorbent assay. IL-6 and p-Stat3 expression were decreased in Epim(-/-) vs WT colon. A relative increase in stromal vs epithelial p-Stat3 expression was observed in WT mice but not in Epim(-/-) mice. Epim deletion abrogates IL-6 secretion from colonic myofibroblasts treated with IL-1β and decreases IL-6 secretion from peritoneal macrophages in a subset of DSS-treated mice. Epim deletion inhibits IL-6 secretion most profoundly from colonic myofibroblasts. Distribution of Stat3 activation is altered in DSS-treated Epim(-/-) mice. Our findings support the notion that myofibroblasts modulate IL-6/p-Stat3 signaling in DSS-treated Epim(-/-) mice.

Synaptobrevin2 is the v-SNARE required for cytotoxic T-lymphocyte lytic granule fusion

Cytotoxic T lymphocytes kill virus-infected and tumorigenic target cells through the release of perforin and granzymes via fusion of lytic granules at the contact site, the immunological synapse. It has been postulated that this fusion process is mediated by non-neuronal members of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex protein family. Here, using a synaptobrevin2-monomeric red fluorescence protein knock-in mouse we demonstrate that, surprisingly, the major neuronal v-SNARE synaptobrevin2 is expressed in cytotoxic T lymphocytes and exclusively localized on granzyme B-containing lytic granules. Cleavage of synaptobrevin2 by tetanus toxin or ablation of the synaptobrevin2 gene leads to a complete block of lytic granule exocytosis while leaving upstream events unaffected, identifying synaptobrevin2 as the v-SNARE responsible for the fusion of lytic granules at the immunological synapse.

Comparative proteomic analysis of peripheral blood mononuclear cells from atopic dermatitis patients and healthy donors

Atopic dermatitis (AD) is a chronic inflammatory skin disease that induces changes in various inflammatory skin cells. The prevalence of AD is as high as 18% in some regions of the world, and is steadily rising. However, the pathophysiology of AD is poorly understood. To identify the proteins involved in AD pathogenesis, a comparative proteomic analysis of protein expression in peripheral blood mononuclear cells isolated from AD patients and healthy donors was conducted. Significant changes were observed in the expressions of fourteen proteins, including the vinculin, PITPNB, and Filamin A proteins. Among the proteins, alpha-SNAP and FLNA decreased significantly, and PITPNB increased significantly in AD patients compared with control subjects; these findings were further confirmed by real-time PCR and Western blot analysis. The comparative proteome data may provide a valuable clue to further understand AD pathogenesis, and several differentially regulated proteins may be used as biomarkers for diagnosis and as target proteins for the development of novel drugs.

Protein kinase Balpha is required for vesicle trafficking and class II presentation of IgA Fc receptor (CD89)-targeted antigen

Ag presentation stimulates Ag-specific adaptive immune responses. FcalphaR (CD89)-mediated capture of IgA-bound exogenous Ag leads to efficient MHC class II Ag presentation by APCs. CD89 signaling is required for trafficking of internalized Ag to specialized multivesicular bodies known as MHC class II compartments (MIIC) and subsequent class II presentation. In the present study, we tested the hypothesis that the vesicle trafficking regulator protein kinase Balpha (PKBalpha) is required for CD89-mediated trafficking to MIIC and Ag presentation. We observed by two independent methods (chemical inhibitors and specific RNA interference) that PKBalpha was required for CD89 trafficking to MIIC and class II Ag presentation. Expression of constitutively active PKBalpha in APCs expressing a mutant CD89 accessory signaling molecule (deficient in CD89/Ag trafficking, processing, and presentation) induced trafficking of CD89 to lamp1-containing late endocytic vesicles, but not class II-containing vesicles (MIIC), or class II Ag presentation. These studies show for the first time that PKBalpha is required for receptor-mediated Ag presentation and suggest the mechanism of action includes regulation of vesicle trafficking.

Cyclic AMP promotes a peripheral distribution of melanosomes and stimulates melanophilin/Slac2-a and actin association

Melanosomes are melanin-containing organelles that belong to a recently individualized group of lysosome-related organelles. Recently, numerous reports have dissected the molecular mechanisms that control melanosome transport, but nothing was known about the possible regulation of melanosome distribution by exogenous physiological stimulus. In the present report, we demonstrate that a physiological melanocyte-differentiating agent such as alpha-melanocyte-stimulating hormone, through the stimulation of the cAMP pathway, induces a rapid centrifugal transport of melanosomes, leading to their accumulation at the dendrite tips of melanocytes. Interestingly, the small GTP binding proteins of the p21Rho family and one of their effectors, p160 Rho-associated kinase, but not PKA, play a key role in redistribution of melanosomes at the extremities of the dendrites. Further, we have investigated, at the molecular level, the effect of cAMP on the different proteins involved in the control of melanosome transport. We demonstrate that cAMP stimulates the expression of Rab27a and rapidly increases the interaction of the melanophilin/Slac2-a with actin. Thus, we propose that the stimulation of the interaction between melanophilin/Slac2-a and actin would allow the rapid accumulation of melanosomes in the actin-rich region of the dendrite extremities.

Overexpression of the disease resistance gene Pto in tomato induces gene expression changes similar to immune responses in human and fruitfly

The Pto gene encodes a serine/threonine protein kinase that confers resistance in tomato (Lycopersicon esculentum) to Pseudomonas syringae pv tomato strains that express the type III effector protein AvrPto. Constitutive overexpression of Pto in tomato, in the absence of AvrPto, activates defense responses and confers resistance to several diverse bacterial and fungal plant pathogens. We have used a series of gene discovery and expression profiling methods to examine the effect of Pto overexpression in tomato leaves. Analysis of the tomato expressed sequence tag database and suppression subtractive hybridization identified 600 genes that were potentially differentially expressed in Pto-overexpressing tomato plants compared with a sibling line lacking Pto. By using cDNA microarrays, we verified changes in expression of many of these genes at various time points after inoculation with P. syringae pv tomato (avrPto) of the resistant Pto-overexpressing line and the susceptible sibling line. The combination of these three approaches led to the identification of 223 POR (Pto overexpression responsive) genes. Strikingly, 40% of the genes induced in the Pto-overexpressing plants previously have been shown to be differentially expressed during the human (Homo sapiens) and/or fruitfly (Drosophila melanogaster) immune responses.

Fusion of human neutrophil phagosomes with lysosomes in vitro: involvement of tyrosine kinases of the Src family and inhibition by mycobacteria

The intracellular killing of microorganisms in phagocytes involves the fusion of lysosomes containing bactericidal factors with phagosomes, and several intracellular pathogens are able to inhibit this fusion event. In this study, we report the reconstitution of phagosome-lysosome fusion in vitro, using an assay based on resonance energy transfer between fluorescent phospholipid analogues that were inserted into whole human NB4-neutrophil membranes from liposomes containing positively charged lipids. Cytosol was required for fusion, and fusion was stimulated 3-fold if this cytosol had been prepared from neutrophils activated by using opsonized zymosan or a combination of the calcium ionophore (A23187) and phorbol myristate acetate (PMA). Fusion was inhibited by the addition of PP1, an inhibitor of Src family protein kinases, or GTPgammaS. We have previously reported that the biogenesis of phagolysosomes in human neutrophils is inhibited by mycobacteria. Here we show that cytosol from cells having internalized live (not heat-killed) Mycobacterium smegmatis or cytosol simply incubated with mycobacteria inhibited fusion, indicating that soluble factors are involved in mycobacterial inhibition of phagosome-lysosome fusion.