Enolase 1 and calreticulin regulate the differentiation and function of mouse mast cells

Alpha Enolase 1 Ubiquitination and Degradation Mediated by Ehrlichia chaffeensis TRP120 Disrupts Glycolytic Flux and Promotes Infection

Ehrlichia chaffeensis modulates numerous host cell processes, including gene transcription to promote infection of the mononuclear phagocyte. Modulation of these host cell processes is directed through E. chaffeensis effectors, including TRP120. We previously reported that TRP120 moonlights as a HECT E3 Ub ligase that ubiquitinates host cell transcription and fate regulators (PCGF5 and FBW7) to promote infection. In this study, we identified a novel TRP120 substrate and examined the relationship between TRP120 and α-enolase (ENO1), a metalloenzyme that catalyzes glycolytic pathway substrate dehydration. Immunofluorescence microscopy and coimmunoprecipitation demonstrated interaction between ENO1 and TRP120, and ubiquitination of ENO-1 by TRP120 was detected in vivo and in vitro. Further, ENO-1 degradation was observed during infection and was inhibited by the proteasomal inhibitor bortezomib. A direct role of TRP120 Ub ligase activity in ENO-1 degradation was demonstrated and confirmed by ectopic expression of TRP120 HECT Ub ligase catalytic site mutant. siRNA knockdown of ENO-1 coincided with increased E. chaffeensis infection and ENO-1 knockdown disrupted glycolytic flux by decreasing the levels of pyruvate and lactate that may contribute to changes in host cell metabolism that promote infection. In addition, we elucidated a functional role of TRP120 auto-ubiquitination as an activating event that facilitates the recruitment of the UbcH5 E2 ubiquitin-conjugating enzyme. This investigation further expands the repertoire of TRP120 substrates and extends the potential role of TRP120 Ub ligase in infection to include metabolic reprogramming.

The Art of Mast Cell Adhesion

Cell adhesion is one of the basic phenomena occurring in a living organism, affecting many other processes such as proliferation, differentiation, migration, or cell viability. Mast cells (MCs) are important elements involved in defending the host against various pathogens and regulating inflammatory processes. Due to numerous mediators, they are contributing to the modulation of many basic cellular processes in a variety of cells, including the expression and functioning of different adhesive molecules. They also express themselves many adhesive proteins, including ICAM-1, ICAM-3, VCAM-1, integrins, L-selectin, E-cadherin, and N-cadherin. These molecules enable MCs to interact with other cells and components of the extracellular matrix (ECM), creating structures such as adherens junctions and focal adhesion sites, and triggering a signaling cascade. A thorough understanding of these cellular mechanisms can create a better understanding of MC biology and reveal new goals for MC targeted therapy. This review will focus on the current knowledge of adhesion mechanisms with the involvement of MCs. It also provides insight into the influence of MCs or MC-derived mediators on the adhesion molecule expression in different cells.

Characterization of protein, long noncoding RNA and microRNA signatures in extracellular vesicles derived from resting and degranulated mast cells

Mast cells (MCs) are known to participate in a variety of patho-physiological processes depending largely on the intragranular mediators and the production of cytokines and chemokines during degranulation. Recently, extracellular vesicles (EVs) have been implicated important functions for MCs, but the components of MC-derived EVs have not yet been well-characterized. In this study, we aimed to identify signatures of proteins, long non-coding RNAs (lncRNAs), and microRNAs (miRNAs) in EVs derived from resting (Rest-EV) and degranulated (Sti-EV) MCs by differential ultracentrifugation. Using tandem mass tag (TMT)-based quantitative proteomics technology and RNA sequencing, we identified a total of 1988 proteins, 397 lncRNAs, and 272 miRNAs in Rest-EV and Sti-EV. The proteins include common EVs markers (cytoskeletal proteins), MCs markers (FcεRI and tryptase), and some preformed MCs mediators (lysosomal enzymes) as well. The global expression profiles of lncRNAs and miRNAs identified, for the first time, from Rest-EV and Sti-EV, strongly suggest a potential regulatory function of MC-derived EVs. We have also performed Western blotting and qRT-PCR analysis to further verify some of the proteins, lncRNAs, and miRNAs identified from Rest-EV and Sti-EV. Our findings will help to elucidate the functions of MC-derived EVs, and provide a reference dataset for future translational studies involving MC-derived EVs.

Modifications of the soluble proteome of a mediterranean strain of the invasive neurotoxic dinoflagellate Alexandrium catenella under metal stress conditions

The soluble proteome of the mediterranean strain ACT03 of the invasive neurotoxic dinoflagellate Alexandrium catenella exposed to lead or zinc at 6, 12 or 18μM (total concentrations), or under control conditions, was characterized by two-dimensional gel electrophoresis (2-DE). Zinc reduced (P<0.05) the total number of protein spots (-41%, -52% and -60%, at 6, 12 or 18μM, respectively). Besides, most of the proteins constituting the soluble proteome were down-regulated in response to lead or zinc stresses. These proteins were involved mainly in photosynthesis (20-37% for lead; 36-50% for zinc) (ribulose-1,5-bisphosphate carboxylase/oxygenase: RUBISCO; ferredoxin-NADP⁺ reductase: FNR; peridinin-chlorophyll a-protein: PCP), and in the oxidative stress response (29-34% for lead; 17-36% for zinc) (superoxide dismutase: SOD; proteasome α/β subunits). These negative effects could be partly compensated by the up-regulation of specific proteins such as ATP-synthase β subunit (+16.3 fold after exposure to lead at 12μM). Indeed, an increase in the abundance of ATP-synthase could enrich the ATP pool and provide more energy available for the cells to survive under metal stress, and make the ATP-synthase transport of metal cations out of the cells more efficient. Finally, this study shows that exposure to lead or zinc have a harmful effect on the soluble proteome of A. catenella ACT03, but also suggests the existence of an adaptative proteomic response to metal stresses, which could contribute to maintaining the development of this dinoflagellate in trace metal-contaminated ecosystems.

The immunoregulatory role of alpha enolase in dendritic cell function during Chlamydia infection

Background

We have previously reported that interleukin-10 (IL-10) deficient dendritic cells (DCs) are potent antigen presenting cells that induced elevated protective immunity against Chlamydia. To further investigate the molecular and biochemical mechanism underlying the superior immunostimulatory property of IL-10 deficient DCs we performed proteomic analysis on protein profiles from Chlamydia-pulsed wild-type (WT) and IL-10^−/− DCs to identify differentially expressed proteins with immunomodulatory properties.

Results

The results showed that alpha enolase (ENO1), a metabolic enzyme involved in the last step of glycolysis was significantly upregulated in Chlamydia-pulsed IL-10^−/− DCs compared to WT DCs. We further studied the immunoregulatory role of ENO1 in DC function by generating ENO1 knockdown DCs, using lentiviral siRNA technology. We analyzed the effect of the ENO1 knockdown on DC functions after pulsing with Chlamydia. Pyruvate assay, transmission electron microscopy, flow cytometry, confocal microscopy, cytokine, T-cell activation and adoptive transfer assays were also used to study DC function. The results showed that ENO1 knockdown DCs had impaired maturation and activation, with significant decrease in intracellular pyruvate concentration as compared with the Chlamydia-pulsed WT DCs. Adoptive transfer of Chlamydia-pulsed ENO1 knockdown DCs were poorly immunogenic in vitro and in vivo, especially the ability to induce protective immunity against genital chlamydia infection. The marked remodeling of the mitochondrial morphology of Chlamydia-pulsed ENO1 knockdown DCs compared to the Chlamydia-pulsed WT DCs was associated with the dysregulation of translocase of the outer membrane (TOM) 20 and adenine nucleotide translocator (ANT) 1/2/3/4 that regulate mitochondrial permeability. The results suggest that an enhanced glycolysis is required for efficient antigen processing and presentation by DCs to induce a robust immune response.

Conclusions

The upregulation of ENO1 contributes to the superior immunostimulatory function of IL-10 deficient DCs. Our studies indicated that ENO1 deficiency causes the reduced production of pyruvate, which then contributes to a dysfunction in mitochondrial homeostasis that may affect DC survival, maturation and antigen presenting properties. Modulation of ENO1 thus provides a potentially effective strategy to boost DC function and promote immunity against infectious and non-infectious diseases.

Proteome analysis identifies L1CAM/CD171 and DPP4/CD26 as novel markers of human skin mast cells

BACKGROUND

The function of skin mast cells has been well documented in IgE-mediated allergic reactions, whereas other mast cell functions are poorly defined. This study aimed at identifying novel mast cell proteins by proteome analysis of primary human skin mast cells.

METHODS

The proteome of skin mast cells was compared to other cell types and analyzed using bioinformatics. The expression and function of two proteins hitherto not described in skin mast cells was investigated in isolated mast cells as well as in mast cells in situ.

RESULTS

Within the mast cell proteome, we identified 49 highly expressed proteins previously not described in mast cells; 21 of these proteins were found to be selectively expressed in mast cells. Two proteins, the neural cell adhesion molecule L1 and dipeptidyl peptidase 4, were further studied. L1 was found to be highly expressed in mast cells in normal, psoriasis, and mastocytosis skin. Dipeptidyl peptidase 4 was found to be expressed in mast cells in normal, psoriasis, and mastocytosis skin as well as in bone marrow mast cells in patients with systemic mastocytosis. In normal skin, mast cells were identified as a major source of dipeptidyl peptidase 4 and we also found that skin mast cells and fibroblasts secrete an active form of this enzyme.

CONCLUSIONS

In a systematic proteomics approach we identified two novel mast cell proteins potentially relevant to skin homeostasis: neural cell adhesion molecule L1 and dipeptidyl peptidase 4.

Enolase 1 (ENO1) and protein disulfide-isomerase associated 3 (PDIA3) regulate Wnt/β-catenin-driven trans-differentiation of murine alveolar epithelial cells

The alveolar epithelium represents a major site of tissue destruction during lung injury. It consists of alveolar epithelial type I (ATI) and type II (ATII) cells. ATII cells are capable of self-renewal and exert progenitor function for ATI cells upon alveolar epithelial injury. Cell differentiation pathways enabling this plasticity and allowing for proper repair, however, are poorly understood. Here, we applied proteomics, expression analysis and functional studies in primary murine ATII cells to identify proteins and molecular mechanisms involved in alveolar epithelial plasticity. Mass spectrometry of cultured ATII cells revealed a reduction of carbonyl reductase 2 (CBR2) and an increase in enolase 1 (ENO1) and protein disulfide-isomerase associated 3 (PDIA3) protein expression during ATII-to-ATI cell trans-differentiation. This was accompanied by increased Wnt/β-catenin signaling, as analyzed by qRT-PCR and immunoblotting. Notably, ENO1 and PDIA3, along with T1α (podoplanin; an ATI cell marker), exhibited decreased protein expression upon pharmacological and molecular Wnt/β-catenin inhibition in cultured ATII cells, whereas CBR2 levels were stabilized. Moreover, we analyzed primary ATII cells from mice with bleomycin-induced lung injury, a model exhibiting activated Wnt/β-catenin signaling in vivo. We observed reduced CBR2 significantly correlating with surfactant protein C (SFTPC), whereas ENO1 and PDIA3 along with T1α were increased in injured ATII cells. Finally, siRNA-mediated knockdown of ENO1, as well as PDIA3, in primary ATII cells led to reduced T1α expression, indicating diminished cell trans-differentiation. Our data thus identified proteins involved in ATII-to-ATI cell trans-differentiation and suggest a Wnt/β-catenin-driven functional role of ENO1 and PDIA3 in alveolar epithelial cell plasticity in lung injury and repair.

Summary: The authors identified proteins involved in Wnt/β-catenin-driven alveolar epithelial plasticity in lung injury and repair.

Comparative proteomic and bioinformatic analysis of the effects of a high-grain diet on the hepatic metabolism in lactating dairy goats

To gain insight on the impart of high-grain diets on liver metabolism in ruminants, we employed a comparative proteomic approach to investigate the proteome-wide effects of diet in lactating dairy goats by conducting a proteomic analysis of the liver extracts of 10 lactating goats fed either a control diet or a high-grain diet. More than 500 protein spots were detected per condition by two-dimensional electrophoresis (2-DE). In total, 52 differentially expressed spots (≥2.0-fold changed) were excised and analyzed using MALDI TOF/TOF. Fifty-one protein spots were successfully identified. Of these, 29 proteins were upregulated, while 22 were downregulated in the high-grain fed vs. control animals. Differential expressions of proteins including alpha enolase, elongation factor 2, calreticulin, cytochrome b5, apolipoprotein A-I, catalase, was verified by mRNA analysis and/or Western blotting. Database searches combined with Gene Ontology (GO) analysis and KEGG pathway analysis revealed that the high-grain diet resulted in altered expression of proteins related to amino acids metabolism. These results suggest new candidate proteins that may contribute to a better understanding of the signaling pathways and mechanisms that mediate liver adaptation to high-grain diet.

Comparative proteomic analysis of the hepatic response to heat stress in Muscovy and Pekin ducks: insight into thermal tolerance related to energy metabolism

The Pekin duck, bred from the mallard (Anas platyrhynchos) in china, is one of the most famous meat duck species in the world. However, it is more sensitive to heat stress than Muscovy duck, which is believed to have originated in South America. With temperature raising, mortality, laying performance, and meat quality of the Pekin duck are severely affected. This study aims to uncover the temperature-dependent proteins of two duck species using comparative proteomic approach. Duck was cultured under 39°C ± 0.5°C for 1 h, and then immediately returned to 20°C for a 3 h recovery period, the liver proteins were extracted and electrophoresed in two-dimensional mode. After analysis of gel images, 61 differentially expressed proteins were detected, 54 were clearly identified by MALDI TOF/TOF MS. Of the 54 differentially expressed protein spots identified, 7 were found in both species, whereas 47 were species specific (25 in Muscovy duck and 22 in Pekin duck). As is well known, chaperone proteins, such as heat shock protein (HSP) 70 and HSP10, were abundantly up-regulated in both species in response to heat stress. However, we also found that several proteins, such as α-enolase, and S-adenosylmethionine synthetase, showed different expression patterns in the 2 duck species. The enriched biological processes were grouped into 3 main categories according to gene ontology analysis: cell death and apoptosis (20.93%), amino acid metabolism (13.95%) and oxidation reduction (20.93%). The mRNA levels of several differentially expressed protein were investigated by real-time RT-PCR. To our knowledge, this study is the first to provide insights into the differential expression of proteins following heat stress in ducks and enables better understanding of possible heat stress response mechanisms in animals.

Changes in the proteomic profiles of mouse brain after infection with cyst-forming Toxoplasma gondii

Background

Toxoplasma gondii is an opportunistic pathogenic protozoan parasite, which infects approximately one third of the human population worldwide, causing opportunistic zoonotic toxoplasmosis. The predilection of T. gondii for the central nervous system (CNS) causes behavioral disorders and fatal necrotizing encephalitis and thus constitutes a major threat especially to AIDS patients.

Methods

In the present study, we explored the proteomic profiles of brain tissues of the specific pathogen-free (SPF) Kunming mice at 7 d, 14 d and 21 d after infection with cysts of the Toxoplasma gondii Prugniaud (PRU) strain (Genotype II), by two-dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF tandem mass spectrometry (MS/MS).

Results

A total of 60 differentially expressed protein spots were selected. Fifty-six spots were successfully identified, which corresponded to 45 proteins of the mouse. Functional analysis using a Gene Ontology database showed that these proteins were mainly involved in metabolism, cell structure, signal transduction and immune responses, and will be beneficial for the understanding of molecular mechanisms of T. gondii pathogenesis.

Conclusions

This study identified some mouse brain proteins involved in the response with cyst-forming T. gondii PRU strain. These results provided an insight into the responsive relationship between T. gondii and the host brain tissues, which will shed light on our understanding of the mechanisms of pathogenesis in toxoplasmic encephalitis, and facilitate the discovery of new methods of diagnosis, prevention, control and treatment of toxoplasmic encephalopathy.

Protein expression from zooplankton communities in a metal contaminated NW mediterranean coastal ecosystem

Bidimensional and monodimensional polyacrylamide gel electrophoresis were used to study protein expression from zooplankton collected in thirteen stations of Toulon Bay (NW Mediterranean). In this ecosystem, Little Bay showed higher trace metal concentrations (13.5-23.8 nM for Cu, 0.73-1.24 nM for Pb, 27.8-58.7 nM for Zn) than Large Bay (Cu 2.2-15.6 nM; Pb 0.19-0.78 nM; Zn 9.0-38.8 nM). Trace metals positively correlated (p < 0.05) with expression of four zooplankton proteins (MW in kDa/pI: 25.0/5.6; 48.8/4.1; 38.2/4.4; 38.3/5.8) and with biomass of Oithona nana, predominant copepod in Little Bay. Sequencing by LC-MS/MS putatively provided zooplankton identity of these proteins: they were cytoskeleton actin, except one protein that was the chaperone calreticulin. We suggest that actin and calreticulin could be regarded as zooplankton markers of metal stress and be involved in a possible tolerance of O. nana to contamination, contributing to its development in a marine perturbed ecosystem.

Smoke-induced signal molecules in bone marrow cells from altered low-density lipoprotein receptor-related protein 5 mice

Mechanism underlying smoke-induced loss of bone mass is unknown. In this study, we hypothesized that protein signals induced by smoking in bone marrow may be associated with the loss of bone mass. Using a proteomics approach, we identified 38 proteins differentially expressed in bone marrow cells from low-density lipoprotein receptor-related protein 5 (Lrp5) mice exposed to cigarette smoking. Smoking effects on protein expression in bone marrow among three genotypes (Lrp5(+/+), Lrp5(G171V), and Lrp5(-/-)) varied. On the basis of the ratio of protein expression induced by smoking versus nonsmoking, smoke induced protein expression significantly in wild-type mice compared to the other two genotypes (Lrp5(G171V) and Lrp5(-/-)). These proteins include inhibitors of β-catenin and proteins associated with differentiation of osteoclasts. We observed that S100A8 and S100A9 were overexpressed in human smokers compared to nonsmokers, which confirmed the effect of smoking on the expression of two proteins in Lrp5 mice, suggesting the role of these proteins in bone remodeling. Smoke induced expression of S100A8 and S100A9 in a time-dependent fashion, which was opposite of the changes in the ratio of OPG/RANKL in bone marrow cells, suggesting that the high levels of S100A8 and S100A9 may be associated with smoke-induced bone loss by increasing bone resorption.