Cyclophilin C-associated protein: a normal secreted glycoprotein that down-modulates endotoxin and proinflammatory responses in vivo

PPIC-labeled CAFs: Key players in neoadjuvant chemotherapy resistance for gastric cancer

BACKGROUND

Gastric cancer (GC) is the fourth leading cause of cancer deaths, with advanced cases having a median survival of less than one year. Neoadjuvant chemotherapy (NCT) is vital but faces drug resistance issues, partly due to cancer-associated fibroblasts (CAFs). Yet, specific CAF subpopulations contributing to resistance are poorly understood.

METHODS

Differentially expressed genes (DEGs) between chemosensitive and resistant GC patients were identified using GEO2R. Single-cell sequencing (scRNA-seq) identified CAF-related genes. Immunohistochemistry verified key genes in NCT-treated GC samples, analyzing their correlation with tumor regression grade (TRG) and clinicopathological characteristics.

RESULTS

PPIC as a gene highly expressed in CAFs was closely associated with NCT resistance in gastric cancer. Immunohistochemistry results revealed positivity for the expression of cyclophilin C (CypC), encoded by PPIC, in the 5-fluorouracil and cisplatin NCT resistant and -sensitive groups of gastric cancer patients at rates of 69.7 % (76/109) and 43.6 % (24/55), respectively (p < 0.001). The high expression of CypC in CAFs was positively correlated to tumor size (p = 0.025), T stage (p = 0.004), TNM stage (p = 0.004), and vascular invasion (p = 0.027). In cancer cells the expression of CypC was associated with OS (p = 0.026). However, in CAFs, CypC expression was not related to OS (p = 0.671).

CONCLUSIONS

PPIC-labeled CAF subgroups are related to NCT resistance and poor prognosis in GC and they may cause drug resistance through signaling pathways such as glucose metabolism and extracellular matrix remodeling. However, the exact mechanism behind the involvement of PPIC-labeled CAF in drug resistance of GC requires further study.

Inhibition of LPS-Induced Inflammatory Response of Oral Mesenchymal Stem Cells in the Presence of Galectin-3

Galectin-3 (GAL-3) is a beta-galactoside binding lectin produced by mesenchymal stem cells (MSCs) and other cell sources under inflammatory conditions. Several studies have reported that GAL-3 exerts an anti-inflammatory action, regulated by its natural ligand GAL-3 BP. In the present study, we aimed to assess the GAL-3 mediated regulation of the MSC function in an LPS-induced inflammation setting. Human gingival mesenchymal stem cells (hGMSCs) were stimulated in vitro with LPSs; the expression of TLR4, NFκB p65, MyD88 and NALP3 were assessed in the hGMSCs via immunofluorescence imaging using confocal microscopy, Western blot assay, and RT-PCR before and after the addition of GAL-3, both alone and with the addition of its inhibitors. LPSs stimulated the expression of TLR4, NFκB p65, MyD88 and NALP3 in hGMSCs, which was inhibited by GAL-3. The addition of either GAL3-BP or the antibody to GAL-3 were able to revert the GAL-3-mediated effects, restoring the expression of TLR4, NFκB p65, MyD88 and NALP3. GAL-3 induces the downregulation of the LPS-induced inflammatory program in MSCs.

Mouse Models for Application in Colorectal Cancer: Understanding the Pathogenesis and Relevance to the Human Condition

Colorectal cancer (CRC) is a malignant disease that is the second most common cancer worldwide. CRC arises from the complex interactions among a variety of genetic and environmental factors. To understand the mechanism of colon tumorigenesis, preclinical studies have developed various mouse models including carcinogen-induced and transgenic mice to recapitulate CRC in humans. Using these mouse models, scientific breakthroughs have been made on the understanding of the pathogenesis of this complex disease. Moreover, the availability of transgenic knock-in or knock-out mice further increases the potential of CRC mouse models. In this review, the overall features of carcinogen-induced (focusing on azoxymethane and azoxymethane/dextran sulfate sodium) and transgenic (focusing on Apc^Min/+) mouse models, as well as their mechanisms to induce colon tumorigenesis, are explored. We also discuss limitations of these mouse models and their applications in the evaluation and study of drugs and treatment regimens against CRC. Through these mouse models, a better understanding of colon tumorigenesis can be achieved, thereby facilitating the discovery of novel therapeutic strategies against CRC.

Differentiating children with sepsis with and without acute respiratory distress syndrome using proteomics

Both sepsis and acute respiratory distress syndrome (ARDS) rely on imprecise clinical definitions leading to heterogeneity, which has contributed to negative trials. Because circulating protein/DNA complexes have been implicated in sepsis and ARDS, we aimed to develop a proteomic signature of DNA-bound proteins to discriminate between children with sepsis with and without ARDS. We performed a prospective case-control study in 12 children with sepsis with ARDS matched to 12 children with sepsis without ARDS on age, severity of illness score, and source of infection. We performed co-immunoprecipitation and downstream proteomics in plasma collected ≤ 24 h of intensive care unit admission. Expression profiles were generated, and a random forest classifier was used on differentially expressed proteins to develop a signature which discriminated ARDS. The classifier was tested in six independent blinded samples. Neutrophil and nucleosome proteins were over-represented in ARDS, including two S100A proteins, superoxide dismutase (SOD), and three histones. Random forest produced a 10-protein signature that accurately discriminated between children with sepsis with and without ARDS. This classifier perfectly assigned six independent blinded samples as having ARDS or not. We validated higher expression of the most informative discriminating protein, galectin-3-binding protein, in children with ARDS. Our methodology has applicability to isolation of DNA-bound proteins from plasma. Our results support the premise of a molecular definition of ARDS, and give preliminary insight into why some children with sepsis, but not others, develop ARDS.

Serum Mac-2 Binding Protein Levels Associate with Metabolic Parameters and Predict Liver Fibrosis Progression in Subjects with Fatty Liver Disease: A 7-Year Longitudinal Study

Background: Mac-2 binding protein (M2BP) is a highly glycosylated secreted glycoprotein that is involved in immune defense and regulation. Our cross-sectional studies indicated that serum M2BP was a useful liver fibrosis biomarker for nonalcoholic fatty liver disease (NAFLD). In this study, we conducted a 7-year longitudinal study to investigate the significance of serum M2BP levels (baseline and at 7-year follow-up) and their relationships with other metabolic parameters of fatty liver disease. Methods: We enrolled 715 study subjects (521 male and 194 female) during health examinations. Study subjects received blood sampling tests and abdominal ultrasound tests at baseline and follow-up. Results: Univariate analyses demonstrated that serum M2BP levels were significantly correlated with various parameters related to metabolic risk (body mass index (BMI), systolic blood pressure, triglyceride, high density lipoprotein (HDL)-cholesterol) and metabolic syndrome diseases (obesity, hypertension, dyslipidemia, diabetes mellitus, fatty liver (FL)). Multiple logistic regression analyses demonstrated that BMI and FL were independent determinants for serum M2BP levels. Baseline serum M2BP levels were significant independent determinants for changes in platelet count, Fibrosis-4 (FIB4) index, and NAFLD fibrosis score. Higher serum M2BP levels (>1.80 μg/mL) strongly correlated with changes in the FIB4-index. Conclusions: The results of this study suggest that changes in serum M2BP levels reflect changes in specific metabolic disease-related parameters, and baseline serum M2BP levels could predict changes in liver fibrosis.

Functional glycomics: Application to medical science and hepatology

Glycomics refers to the comprehensive analysis of glycans. Recent progress in glycotechnology enables the determination of a variety of biological functions of glycans. Among different glycosylation patterns, certain types of aberrant glycosylation are linked to cancer and/or inflammation, and thus have biological importance. Glycotechnology has been applied to many fields of medical science, including hepatology. In particular, dramatic changes in glycosylation are observed in the progression of liver diseases. As the liver produces so many serum glycoproteins, changes in glycosylation of these proteins might provide useful disease biomarkers. Furthermore, many patients with genetic diseases of glycosylation who have liver dysfunction have been found as a result from whole genome sequencing, and various kinds of glycotherapy have been developed, especially in immunotherapy. In this review, we describe our basic knowledge of glycobiology and discuss the application of these data to medical science, especially hepatology.

Viperin Differentially Induces Interferon-Stimulated Genes in Distinct Cell Types

Viperin is an IFN-stimulated gene (ISG)-encoded protein that was identified in human primary macrophages treated with IFN-γ and in human primary fibroblasts infected with cytomegalovirus (CMV). This protein plays multiple roles in various cell types. It inhibits viral replication, mediates signaling pathways, and regulates cellular metabolism. Recent studies have shown that viperin inhibits IFN expression in macrophages, while it enhances TLR7 and TLR9-mediated IFN production in plasmacytoid dendritic cells, suggesting that viperin can play different roles in activation of the same pathway in different cell types. Viperin also controls induction of ISGs in macrophages. However, the effect of viperin on induction of ISGs in cell types other than macrophages is unknown. Here, we show that viperin differentially induces ISGs in 2 distinct cell types, macrophages and fibroblasts isolated from wild type and viperin knockout mice. Unlike in bone marrow-derived macrophages (BMDMs), viperin downregulates the expression levels of ISGs such as bone marrow stromal cell antigen-2, Isg15, Isg54, myxovirus resistance dynamin like GTPase 2, and guanylate binding protein 2 in murine embryonic fibroblasts (MEFs) treated with type I or II IFN. However, viperin upregulates expression of these ISGs in both BMDMs and MEFs stimulated with polyinosinic-polycytidylic acid or CpG DNA and infected with murine CMV. The efficiency of viral entry is inversely proportional to the expression levels of ISGs in both cell types. The data indicate that viperin differentially regulates induction of ISGs in a cell type-dependent manner, which might provide different innate immune responses in distinct cell types against infections.

Comparative two time-point proteome analysis of the plasma from preterm infants with and without bronchopulmonary dysplasia

BACKGROUND

In this study, we aimed to analyze differences in plasma protein abundances between infants with and without bronchopulmonary dysplasia (BPD), to add new insights into a better understanding of the pathogenesis of this disease.

METHODS

Cord and peripheral blood of neonates (≤ 30 weeks gestational age) was drawn at birth and at the 36th postmenstrual week (36 PMA), respectively. Blood samples were retrospectively subdivided into BPD(+) and BPD(-) groups, according to the development of BPD.

RESULTS

Children with BPD were characterized by decreased afamin, gelsolin and carboxypeptidase N subunit 2 levels in cord blood, and decreased galectin-3 binding protein and hemoglobin subunit gamma-1 levels, as well as an increased serotransferrin abundance in plasma at the 36 PMA.

CONCLUSIONS

BPD development is associated with the plasma proteome changes in preterm infants, adding further evidence for the possible involvement of disturbances in vitamin E availability and impaired immunological processes in the progression of prematurity pulmonary complications. Moreover, it also points to the differences in proteins related to infection resistance and maintaining an adequate level of hematocrit in infants diagnosed with BPD.

Inducible LGALS3BP/90K activates antiviral innate immune responses by targeting TRAF6 and TRAF3 complex

The galectin 3 binding protein (LGALS3BP, also known as 90K) is a ubiquitous multifunctional secreted glycoprotein originally identified in cancer progression. It remains unclear how 90K functions in innate immunity during viral infections. In this study, we found that viral infections resulted in elevated levels of 90K. Further studies demonstrated that 90K expression suppressed virus replication by inducing IFN and pro-inflammatory cytokine production. Upon investigating the mechanisms behind this event, we found that 90K functions as a scaffold/adaptor protein to interact with TRAF6, TRAF3, TAK1 and TBK1. Furthermore, 90K enhanced TRAF6 and TRAF3 ubiquitination and served as a specific ubiquitination substrate of TRAF6, leading to transcription factor NF-κB, IRF3 and IRF7 translocation from the cytoplasm to the nucleus. Conclusions: 90K is a virus-induced protein capable of binding with the TRAF6 and TRAF3 complex, leading to IFN and pro-inflammatory production.

The innate immune system detects the presence of viruses through germline-encoded pattern-recognition receptors (PRRs) and leads to the production of proinflammatory cytokines and interferons (IFNs) as the first line of defense against viral infections. Here, we identified a host protein, LGALS3BP, as a positive regulator of PRR-mediated signal transduction pathways by interacting with TRAF6-TAK1 and TRAF3-TBK1 axes, enhancing their recruitment and promoting the ubiquitination of TRAF6 and TRAF3. LGALS3BP exhibited antiviral activity toward a broad range of viral infections. LGALS3BP^-/- mice are highly susceptible to lethal influenza A virus infection with increasing pulmonary viral load, morbidity and mortality. Thus, our study highlight the importance of LGALS3BP in host antiviral innate immune responses.

Gal-3BP Negatively Regulates NF-κB Signaling by Inhibiting the Activation of TAK1

Galectin-3-binding protein (Gal-3BP) is a member of the family of scavenger receptor cysteine-rich (SRCR) domain-containing proteins, which are associated with the immune system. However, the functional roles and signaling mechanisms of Gal-3BP in host defense and the immune response remain largely unknown. Here, we identified cellular Gal-3BP as a negative regulator of NF-κB activation and proinflammatory cytokine production in lipopolysaccharide (LPS)-stimulated murine embryonic fibroblasts (MEFs). Furthermore, cellular Gal-3BP interacted with transforming growth factor β-activated kinase 1 (TAK1), a crucial mediator of NF-κB activation in response to cellular stress. Gal-3BP inhibited the phosphorylation of TAK1, leading to suppression of its kinase activity and reduced protein stability. In vivo we found that Lgals3BP deficiency in mice enhanced LPS-induced proinflammatory cytokine release and rendered mice more sensitive to LPS-induced endotoxin shock. Overall, these results suggest that Gal-3BP is a novel suppressor of TAK1-dependent NF-κB activation that may have potential in the prevention and treatment of inflammatory diseases.

Galectin-3-binding protein: A multitask glycoprotein with innate immunity functions in viral and bacterial infections

Galectin-3-binding protein (Gal-3BP) is a ubiquitous and multifunctional secreted glycoprotein originally identified and mainly studied in the context of neoplastic transformation and cancer progression. However, Gal-3BP expression is induced in viral infection and by a multitude of molecules that either mimic or are characteristic for an ongoing inflammation and microbial infection, such as IFN-α, IFN-β, IFN-γ, TNF-α, poly(I:C), dsRNA, and dsDNA. Furthermore, Gal-3BP belongs to the scavenger receptor cysteine-rich (SRCR) domain-containing protein family, by virtue of its N-terminal SRCR domain. The SRCR domain is found in soluble or membrane-associated innate immunity-related proteins and is implicated in self-nonself discrimination. This review summarizes the current knowledge of structural features of Gal-3BP and its proposed intracellular and extracellular innate immunity functions with special emphasis on viral and bacterial infections.

Galectin-3 binding protein, coronary artery disease and cardiovascular mortality: Insights from the LURIC study

BACKGROUND AND AIMS

Galectin-3 binding protein (Gal-3BP) has been associated with inflammation and cancer, however, its role in coronary artery disease (CAD) and cardiovascular outcome remains unclear.

METHODS

Gal-3BP plasma levels were measured by ELISA in 2922 individuals from the LURIC study (62.7 ± 10.6 years, 62.7% male). All-cause and cardiovascular mortality was assessed by Kaplan-Meier analysis and Cox proportional hazards regression. Causal involvement of Gal-3BP was tested for by Mendelian randomization. Gal-3BP effects on human monocyte-derived macrophages were assessed in vitro.

RESULTS

During 8.8 ± 3.0 years, 866 individuals died, 654 of cardiovascular causes. There was a significant increase in all-cause and cardiovascular mortality with increasing Gal-3BP quintiles. After thorough adjustment, all-cause mortality remained significantly increased in the fifth Gal-3BP quintile (HR_Q5 1.292 (1.030-1.620), p = 0.027); cardiovascular mortality remained increased in Gal-3BP quintiles two to five (HR_Q51.433 (1.061-1.935, p = 0.019). Gal-3BP levels were not associated with diagnosis and extent of coronary artery disease. In addition, Mendelian randomization did not show a direct causal relationship between Gal-3BP levels and mortality. Gal-3BP levels were, however, independently associated with markers of metabolic and inflammatory distress. In vitro, Gal-3BP induced a pro-inflammatory response in human monocyte-derived macrophages. Adding Gal-3BP levels to the ESC score improved risk assessment in patients with ESC SCORE-based risk >5% (p = 0.010).

CONCLUSIONS

In a large clinical cohort of CAD patients, Gal-3BP levels are independently associated with all-cause and cardiovascular mortality. The underlying mechanisms may likely involve metabolic and inflammatory distress. To further evaluate the potential clinical value of Gal-3BP, prospective studies are needed.

PPIC, EMP3 and CHI3L1 Are Novel Prognostic Markers for High Grade Glioma

Current treatment methods for patients diagnosed with gliomas have shown limited success. This is partly due to the lack of prognostic genes available to accurately predict disease outcomes. The aim of this study was to investigate novel prognostic genes based on the molecular profile of tumor samples and their correlation with clinical parameters. In the current study, microarray data (GSE4412 and GSE7696) downloaded from Gene Expression Omnibus were used to identify differentially expressed prognostic genes (DEPGs) by significant analysis of microarray (SAM) between long-term survivors (>2 years) and short-term survivors (≤2 years). DEPGs generated from these two datasets were intersected to obtain a list of common DEPGs. The expression of a subset of common DEPGs was then independently validated by real-time reverse transcription quantitative PCR (qPCR). Survival value of the common DEPGs was validated using known survival data from the GSE4412 and TCGA dataset. After intersecting DEPGs generated from the above two datasets, three genes were identified which may potentially be used to determine glioma patient prognosis. Independent validation with glioma patients tissue (n = 70) and normal brain tissue (n = 19) found PPIC, EMP3 and CHI3L1 were up-regulated in glioma tissue. Survival value validation showed that the three genes correlated with patient survival by Kaplan-Meir analysis, including grades, age and therapy.

Galectin-3 Binding Protein Secreted by Breast Cancer Cells Inhibits Monocyte-Derived Fibrocyte Differentiation

To metastasize, tumor cells often need to migrate through a layer of collagen-containing scar tissue which encapsulates the tumor. A key component of scar tissue and fibrosing diseases is the monocyte-derived fibrocyte, a collagen-secreting profibrotic cell. To test the hypothesis that invasive tumor cells may block the formation of the fibrous sheath, we determined whether tumor cells secrete factors that inhibit monocyte-derived fibrocyte differentiation. We found that the human metastatic breast cancer cell line MDA-MB-231 secretes activity that inhibits human monocyte-derived fibrocyte differentiation, whereas less aggressive breast cancer cell lines secrete less of this activity. Purification indicated that Galectin-3 binding protein (LGALS3BP) is the active factor. Recombinant LGALS3BP inhibits monocyte-derived fibrocyte differentiation, and immunodepletion of LGALS3BP from MDA-MB 231 conditioned media removes the monocyte-derived fibrocyte differentiation-inhibiting activity. LGALS3BP inhibits the differentiation of monocyte-derived fibrocytes from wild-type mouse spleen cells, but not from SIGN-R1(-/-) mouse spleen cells, suggesting that CD209/SIGN-R1 is required for the LGALS3BP effect. Galectin-3 and galectin-1, binding partners of LGALS3BP, potentiate monocyte-derived fibrocyte differentiation. In breast cancer biopsies, increased levels of tumor cell-associated LGALS3BP were observed in regions of the tumor that were invading the surrounding stroma. These findings suggest LGALS3BP and galectin-3 as new targets to treat metastatic cancer and fibrosing diseases.

Zebrafish Bone and General Physiology Are Differently Affected by Hormones or Changes in Gravity

Teleost fish such as zebrafish (Danio rerio) are increasingly used for physiological, genetic and developmental studies. Our understanding of the physiological consequences of altered gravity in an entire organism is still incomplete. We used altered gravity and drug treatment experiments to evaluate their effects specifically on bone formation and more generally on whole genome gene expression. By combining morphometric tools with an objective scoring system for the state of development for each element in the head skeleton and specific gene expression analysis, we confirmed and characterized in detail the decrease or increase of bone formation caused by a 5 day treatment (from 5dpf to 10 dpf) of, respectively parathyroid hormone (PTH) or vitamin D3 (VitD3). Microarray transcriptome analysis after 24 hours treatment reveals a general effect on physiology upon VitD3 treatment, while PTH causes more specifically developmental effects. Hypergravity (3g from 5dpf to 9 dpf) exposure results in a significantly larger head and a significant increase in bone formation for a subset of the cranial bones. Gene expression analysis after 24 hrs at 3g revealed differential expression of genes involved in the development and function of the skeletal, muscular, nervous, endocrine and cardiovascular systems. Finally, we propose a novel type of experimental approach, the "Reduced Gravity Paradigm", by keeping the developing larvae at 3g hypergravity for the first 5 days before returning them to 1g for one additional day. 5 days exposure to 3g during these early stages also caused increased bone formation, while gene expression analysis revealed a central network of regulatory genes (hes5, sox10, lgals3bp, egr1, edn1, fos, fosb, klf2, gadd45ba and socs3a) whose expression was consistently affected by the transition from hyper- to normal gravity.

Anti-inflammatory deficiencies in neutrophilic asthma: reduced galectin-3 and IL-1RA/IL-1β

BACKGROUND

Galectin-3 (gal-3), a member of the β-galactoside-binding animal lectins, is involved in the recruitment, activation and removal of neutrophils. Neutrophilic asthma is characterized by a persistent elevation of airway neutrophils and impaired efferocytosis. We hypothesized that sputum gal-3 would be reduced in neutrophilic asthma and the expression of gal-3 would be associated with other markers of neutrophilic inflammation.

METHODS

Adults with asthma (n = 80) underwent a sputum induction following clinical assessment and blood collection. Sputum was dispersed for a differential cell count and ELISA assessment of gal-3, gal-3 binding protein (BP), interleukin (IL)-1β, IL-1 receptor antagonist (RA), IL-8 and IL-6. Gal-3 and gal-3BP immunoreactivity were assessed in mixed sputum cells.

RESULTS

Sputum gal-3 (median, (q1,q3)) was significantly reduced in neutrophilic asthma (183 ng/mL (91,287)) compared with eosinophilic (293 ng/mL (188,471), p = 0.021) and paucigranulocytic asthma (399 ng/mL (213,514), p = 0.004). The gal-3/gal-3BP ratio and IL-1RA/IL-1β ratio were significantly reduced, while gal-3BP and IL-1β were significantly elevated in neutrophilic asthma compared with eosinophilic and paucigranulocytic asthma.

CONCLUSION

Patients with neutrophilic asthma have impairment in anti-inflammatory ratio of gal-3/gal-3BP and IL-1RA/IL-1β which provides a further framework for exploration into pathologic mechanisms of asthma phenotypes.

Ziploc-ing the structure: Triple helix formation is coordinated by rough endoplasmic reticulum resident PPIases

BACKGROUND

Protein folding is crucial for proteins' specific functions and is facilitated by various types of enzymes and molecular chaperones. The peptidyl prolyl cis/trans isomerases (PPIase) are one of these families of enzymes. They ubiquitously exist inside the cell and there are eight PPIases in the rough endoplasmic reticulum (rER), a compartment where the folding of most secreted proteins occurs.

SCOPE OF REVIEW

We review the functional and structural aspects of individual rER resident PPIases. Furthermore, we specifically discuss the role of these PPIases during collagen biosynthesis, since collagen is the most abundant protein in humans, is synthesized in the rER, and contains a proportionally high number of proline residues.

MAJOR CONCLUSIONS

The rER resident PPIases recognize different sets of substrates and facilitate their folding. Although they are clearly catalysts for protein folding, they also have more broad and multifaceted functions. We propose that PPIases coordinate collagen biosynthesis in the rER.

GENERAL SIGNIFICANCE

This review expands our understanding of collagen biosynthesis by explaining the influence of novel indirect mechanisms of regulating folding and this is also explored for PPIases. We also suggest future directions of research to obtain a better understanding of collagen biosynthesis and functions of PPIases in the rER. This article is part of a Special Issue entitled Proline-directed Foldases: Cell Signaling Catalysts and Drug Targets.

Lectin galactoside-binding soluble 3 binding protein (LGALS3BP) is a tumor-associated immunomodulatory ligand for CD33-related Siglecs

Lectin galactoside-binding soluble 3 binding protein (LGALS3BP, also called Mac-2 binding protein) is a heavily glycosylated secreted molecule that has been shown previously to be up-regulated in many cancers and has been implicated in tumor metastatic processes, as well as in other cell adhesion and immune functions. The CD33-related subset of sialic acid-binding immunoglobulin-like lectins (Siglecs) consists of immunomodulatory molecules that have recently been associated with the modulation of immune responses to cancer. Because up-regulation of Siglec ligands in cancer tissue has been observed, the characterization of these cancer-associated ligands that bind to inhibitory CD33-related Siglecs could provide novel targets for cancer immunomodulatory therapy. Here we used affinity chromatography of tumor cell extracts to identify LGALS3BP as a novel sialic acid-dependent ligand for human Siglec-9 and for other immunomodulatory Siglecs, such as Siglec-5 and Siglec-10. In contrast, the mouse homolog Siglec-E binds to murine LGALS3BP with lower affinity. LGALS3BP has been observed to be up-regulated in human colorectal and prostate cancer specimens, particularly in the extracellular matrix. Finally, LGALS3BP was able to inhibit neutrophil activation in a sialic acid- and Siglec-dependent manner. These findings suggest a novel immunoinhibitory function for LGALS3BP that might be important for immune evasion of tumor cells during cancer progression.

β-Arrestin 2 negatively regulates Toll-like receptor 4 (TLR4)-triggered inflammatory signaling via targeting p38 MAPK and interleukin 10

The control of IL-10 production in Toll-like receptor (TLR) signals remains to be elucidated. Here, we report that β-arrestin 2 positively regulates TLR-triggered IL-10 production in a p38 mitogen-activated protein kinase (MAPK)-dependent mechanism. In vitro studies with cells including peritoneal macrophages and HEK293/TLR4 cells have demonstrated that β-arrestin 2 forms complexes with p38 and facilitates p38 activation after lipopolysaccharide (LPS) stimulation. Deficiency of β-arrestin 2 and inhibition of p38 MAPK activity both ameliorate TLR4-stimulated IL-10 response. Additionally, in vivo experiments show that mice lacking β-arrestin 2 produce less amount of IL-10, and are more susceptible to LPS-induced septic shock which is further enhanced by blocking IL-10 signal. These results reveal a novel mechanism by which β-arrestin 2 negatively regulates TLR4-mediated inflammatory reactions.

90K, an interferon-stimulated gene product, reduces the infectivity of HIV-1

BACKGROUND

In response to viral infections, interferons induce the transcription of several hundred genes in mammalian cells. Specific antiviral functions, however, have only been attributed to a few of them. 90K/LGALS3BP has been reported to be an interferon-stimulated gene that is upregulated in individuals with cancer or HIV-1 infection.

RESULTS

Here, we show that 90K expression dose-dependently decreased the particle infectivity of HIV-1 progeny. The lower infectivity of released particles correlated with reduced virion incorporation of mature envelope glycoproteins gp120 and gp41. Further, proteolytic processing of the gp160 precursor and surface expression of gp120 in the producer cell were impaired in the presence of 90K expression. In contrast, expression of Gag, Nef and Vpu, and virus release were not grossly affected by 90K expression. 90K-imposed restriction occurred in the absence of direct interaction of 90K with HIV-1 Env or entrapment of Env in the ER. The cell-associated, but not the secreted species of 90K, mediated the antiviral effect. A truncated version of human 90K, solely consisting of the two intermediate domains, displayed a similar antiviral activity as the full-length wildtype 90K, indicating that the N-terminal SRCR-like domain and the C-terminal domain are dispensable for 90K's antiviral activity. The murine homolog of 90K, CypCAP (Cyclophilin C-associated protein), neither modulated particle infectivity of HIV-1 nor lowered the virion incorporation of mature gp120, suggesting a species-specific mode of action. 90K was expressed at basal levels in TZM-bl cells and in primary macrophages, and at low levels in CD4⁺ T-cells and PBMCs. 90K's susceptibility to IFN-mediated stimulation of expression was cell type-specific. siRNA-mediated knockdown of 90K in TZM-bl cells and primary macrophages enhanced the incorporation of Env glycoproteins into progeny virions, boosted the particle infectivity of released HIV-1, and accelerated HIV-1 spread. Conversely, treatment of HIV-1 infected macrophages with IFN-α induced 90K expression and lowered the particle infectivity of HIV-1.

CONCLUSIONS

Thus, 90K constitutes a novel antiviral factor that reduces the particle infectivity of HIV-1, involving interference with the maturation and incorporation of HIV-1 Env molecules into virions.

MiR-29c is downregulated in gastric carcinomas and regulates cell proliferation by targeting RCC2

Background

Previously, using miRNA microarray, we have found that miR-29c is significantly downregulated in advanced gastric carcinoma. In the present study, we investigated whether miR-29c functions as a tumor-suppressor miRNA in gastric carcinoma cells. For this purpose, we verified the downregulation of miR-29c in gastric carcinoma tissues, and assessed the biological effect of miR-29c on gastric carcinoma cells.

Results

In miR-29c-transfected cells, both proliferation and colony formation ability on soft agar were significantly decreased. Although apoptosis was not induced, BrdU incorporation and the proportion of cells positive for phospho-histone H3 (S10) were significantly decreased in miR-29c-transfected cells, indicating that miR-29c may be involved in the regulation of cell proliferation. To explain the mechanism of growth suppression by miR-29c, we explored differentially expressed genes (>2-fold) in miR-29c-transfected cells in comparison with negative control transfected cells using microarray. RCC2, PPIC and CDK6 were commonly downregulated in miR-29c-transfected MKN45, MKN7 and MKN74 cells, and all of the genes harbored miR-29c target sequences in the 3’-UTR of their mRNA. RCC2 and PPIC were actually upregulated in gastric carcinoma tissues, and therefore both were identified as possible targets of miR-29c in gastric carcinoma. To ascertain whether downregulation of RCC2 and/or PPIC is involved in the growth suppression by miR-29c, we transfected siRNAs against RCC2 and PPIC into MKN45 and determined cell viability, the rate of BrdU incorporation, and caspase activity. We found that RCC2-knockdown decreased both cell viability and BrdU incorporation without any increase of caspase activity, while PPIC-knockdown did not, indicating that downregulation of RCC2 may be at least partly responsible for the growth suppression by miR-29c.

Conclusions

Our findings indicate that miR-29c may have tumor-suppressive functions in gastric carcinoma cells, and that its decreased expression may confer a growth advantage on tumor cells via aberrant expression of RCC2.

Co-purification of Mac-2 binding protein with galectin-3 and association with prostasomes in human semen

BACKGROUND

Prostasomes are exosome-like vesicles that are secreted by the prostate and incorporated into semen during ejaculation. Human prostasomes are proposed to function in regulation of sperm function, immunosuppression, and prostate cancer progression. Previously, we identified galectin-3 on the surface of prostasomes. Galectin-3 is a β-galactoside binding protein involved in immunomodulation, cell interactions, and cancer progression, including prostate cancer. Functional characterization of galectin-3 in a given biological environment includes identification of its target glycoprotein ligands.

METHODS

Candidate galectin-3 ligands in prostasomes were identified by tandem mass spectrometry of proteins that co-purified with galectin-3 during lactose affinity chromatography. Immunochemical and biochemical methods were used to investigate the association of Mac-2 binding protein (M2BP) with prostasomes.

RESULTS

Proteins identified by tandem mass spectrometry included M2BP, CD26/dipeptidyl peptidase IV, prolactin-inducible protein (PIP), olfactomedin-4 (OLFM4), and semenogelins I and II (SgI and SgII). M2BP is a known galectin-3 ligand that was not previously described in prostasomes. M2BP protein bands were detected in the testis, epididymis, vas deferens, prostate, seminal vesicle, and sperm extracts. In seminal plasma, M2BP was identified in the soluble fraction and in purified prostasomes. Surface biotinylation and immunofluorescence studies indicated that M2BP is present on the prostasome surface and on sperm, respectively.

CONCLUSIONS

M2BP, CD26, PIP, OLFM4, and SgI and SgII are candidate glycoprotein ligands for galectin-3 in prostasomes. Given their overlap in functional significance with prostasomes and galectin-3, the identification of these glycoproteins as galectin-3 ligands in prostasomes lays the groundwork for future studies of prostasomes in reproduction and prostate cancer.

Cyclophilin C-associated protein/Mac-2 binding protein colocalizes with calnexin and regulates the expression of tissue transglutaminase

Cyclophilin C-associated protein (CyCAP) or Mac-2 binding protein has been identified as a binding protein for cyclophilin C in mice and for Mac-2 (galectin-3) in human, suggesting its multiple binding activity to proteins. In the present study, using specific anti-rat-CyCAP antibody, we found that CyCAP colocalizes with calnexin at the location near the nuclear envelope, however CyCAP does not have colocalization with calreticulin. In senescent fibroblasts and interferon-gamma (IFNgamma) treated fibroblasts, both calnexin and CyCAP form larger polymers and are released from the endoplasmic reticulum (ER) through the cellular membrane to the extracellular area. Immunoprecipitation studies further confirm that the release of calnexin is through binding to CyCAP. Further, we found that tissue transglutaminase (tTG) protein is decreased, however not at the RNA level, in CyCAP null fibroblasts, which suggests that CyCAP is involved in tTG post-translational modification. Our data give novel evidence that CyCAP regulates the post-translational modification of tTG through its colocalization with calnexin in ER.

Multiple cyclophilins involved in different cellular pathways mediate HCV replication

Three cyclophilin inhibitors (DEBIO-025, SCY635, and NIM811) are currently in clinical trials for hepatitis C therapy. The mechanism of action of these, however, is not completely understood. There are at least 16 cyclophilins expressed in human cells which are involved in a diverse set of cellular processes. Large-scale siRNA experiments, chemoproteomic assays with cyclophilin binding compounds, and mRNA profiling of HCV replicon containing cells were used to identify the cyclophilins that are instrumental to HCV replication. The previously reported cyclophilin A was confirmed and additional cyclophilin containing pathways were identified. Together, the experiments provide strong evidence that NIM811 reduces viral replication by inhibition of multiple cyclophilins and pathways with protein trafficking as the most strongly and persistently affected pathway.

The tumor-associated antigen 90K/Mac-2-binding protein secreted by human colon carcinoma cells enhances extracellular levels of promatrilysin and is a novel substrate of matrix metalloproteinases-2, -7 (matrilysin) and -9: Implications of proteolytic cleavage

BACKGROUND

The tumor-associated antigen 90K (TAA90K)/Mac-2-binding protein is expressed at elevated level in cancerous tissues and associated with poor prognosis. Since TAA90K has been implicated in the restructuring of the extracellular matrix, we examined the functional relationship between colon cancer cell-derived TAA90K and the matrix metalloproteinase (MMP) promatrilysin (proMMP-7), and also tested whether TAA90K is a novel substrate for MMPs-2, -7 and -9.

METHODS

The effect of TAA90K on proMMP-7 levels in HT-29 conditioned media was quantified by enzyme-linked immunosorbent assays. Binding of TAA90K to MMPs, extracellular matrix proteins and galectin-3 was measured by solid-phase binding assays. Proteolytic cleavage of TAA90K by MMPs was documented by SDS-PAGE and protein sequencing analysis.

RESULTS

TAA90K enhanced extracellular levels of proMMP-7 in HT-29 cells. In addition, TAA90K was cleaved by MMPs-2, -7 and -9. MMP-7-mediated cleavage of TAA90K did not affect its binding to MMP-7, laminin-1, collagen IV and galectin-3 but reduced its interaction with fibronectin and laminin-10, and lowered the levels of proMMP-7 in the HT-29 medium.

CONCLUSION

TAA90K is a novel substrate for MMPs-2, -7 and -9 and modulates proMMP-7 levels in colon cancer cells.

GENERAL SIGNIFICANCE

Proteolytic cleavage of TAA90K may have functional implications in colon cancer.

Cyclophilin C-associated protein (CyCAP) knock-out mice spontaneously develop colonic mucosal hyperplasia and exaggerated tumorigenesis after treatment with carcinogen azoxymethane

BACKGROUND

The discovery of a "serrated neoplasia pathway" has highlighted the role of hyperplastic lesions of the colon as the significant precursor of colorectal adenocarcinoma. In mice, hyperplasia of the colonic mucosa is a regular phenomenon after a challenge with colonic carcinogens indicating that mucosal hyperproliferation and thickening, even without cytological dysplasia, represents an early pre-malignant change. Cyclophilin C-associated protein (CyCAP) has been described to down-modulate endotoxin signaling in colorectal murine mucosa and is a murine orthologue of the tumor-associated antigen 90 K (TAA90K)/mac-2-binding protein.

METHODS

Female Balb/c wild-type (WT) and CyCAP knock-out (KO) mice (6-8 weeks old) were administered 2 or 6 weekly subcutaneous injections of azoxymethane. The animals were evaluated post-injection at six weeks for aberrant crypt foci (ACF) study and at five months for colon tumor measurement. The thickness of the colon crypts was measured in microns and the number of colonocytes per crypt was also determined in well-oriented crypts. Morphometric analyses of the colon mucosa were also performed in untreated 6-8 weeks old KO and WT animals. Formalin-fixed/paraffin-embedded colon sections were also studied by immunohistochemistry to determine the Ki-67 proliferation fraction of the colon mucosa, beta-catenin cellular localization, cyclin D1, c-myc, and lysozyme in Paneth cells.

RESULTS

Cyclophilin C-associated protein (CyCAP)-/- mice, spontaneously developed colonic mucosal hyperplasia early in life compared to wild-type mice (WT) (p < 0.0001, T-test) and crypts of colonic mucosa of the (CyCAP)-/- mice show higher proliferation rate (p = 0.039, Mann-Whitney Test) and larger number of cyclin D1-positive cells (p < 0.0001, Mann-Whitney Test). Proliferation fraction and cyclin D1 expression showed positive linear association (p = 0.019, Linear-by-Linear Association). The hyperplasia was even more pronounced in CyCAP-/- mice than in WT after challenge with azoxymethane (p = 0.005, T-test). The length of the crypts (r = 0.723, p = 0.018, Spearman Correlation) and the number of colonocytes per crypt (r = 0.863, p = 0.001, Spearman Correlation) in non-tumorous areas were positively associated with azoxymethane-induced number of tumors. CyCAP-/- developed larger numbers of tumors than WT animals (p = 0.003, T-Test) as well as overall larger tumor mass (p = 0.016, T-Test). Membranous beta-catenin was focally overexpressed in KO mice including proliferative zone of the crypts.

CONCLUSION

CyCAP-/- represent the first described model of spontaneous colonic mucosal hyperplasia. We conclude that CyCAP-deficient mice spontaneously and after challenge with carcinogen develop significantly more colorectal mucosal hyperplasia, an early stage in murine colonic carcinogenesis.

Neurological and behavioral abnormalities, ventricular dilatation, altered cellular functions, inflammation, and neuronal injury in brains of mice due to common, persistent, parasitic infection

BACKGROUND

Worldwide, approximately two billion people are chronically infected with Toxoplasma gondii with largely unknown consequences.

METHODS

To better understand long-term effects and pathogenesis of this common, persistent brain infection, mice were infected at a time in human years equivalent to early to mid adulthood and studied 5-12 months later. Appearance, behavior, neurologic function and brain MRIs were studied. Additional analyses of pathogenesis included: correlation of brain weight and neurologic findings; histopathology focusing on brain regions; full genome microarrays; immunohistochemistry characterizing inflammatory cells; determination of presence of tachyzoites and bradyzoites; electron microscopy; and study of markers of inflammation in serum. Histopathology in genetically resistant mice and cytokine and NRAMP knockout mice, effects of inoculation of isolated parasites, and treatment with sulfadiazine or alphaPD1 ligand were studied.

RESULTS

Twelve months after infection, a time equivalent to middle to early elderly ages, mice had behavioral and neurological deficits, and brain MRIs showed mild to moderate ventricular dilatation. Lower brain weight correlated with greater magnitude of neurologic abnormalities and inflammation. Full genome microarrays of brains reflected inflammation causing neuronal damage (Gfap), effects on host cell protein processing (ubiquitin ligase), synapse remodeling (Complement 1q), and also increased expression of PD-1L (a ligand that allows persistent LCMV brain infection) and CD 36 (a fatty acid translocase and oxidized LDL receptor that mediates innate immune response to beta amyloid which is associated with pro-inflammation in Alzheimer's disease). Immunostaining detected no inflammation around intra-neuronal cysts, practically no free tachyzoites, and only rare bradyzoites. Nonetheless, there were perivascular, leptomeningeal inflammatory cells, particularly contiguous to the aqueduct of Sylvius and hippocampus, CD4+ and CD8+ T cells, and activated microglia in perivascular areas and brain parenchyma. Genetically resistant, chronically infected mice had substantially less inflammation.

CONCLUSION

In outbred mice, chronic, adult acquired T. gondii infection causes neurologic and behavioral abnormalities secondary to inflammation and loss of brain parenchyma. Perivascular inflammation is prominent particularly contiguous to the aqueduct of Sylvius and hippocampus. Even resistant mice have perivascular inflammation. This mouse model of chronic T. gondii infection raises questions of whether persistence of this parasite in brain can cause inflammation or neurodegeneration in genetically susceptible hosts.

Tumor stroma marker endosialin (Tem1) is a binding partner of metastasis-related protein Mac-2 BP/90K

Tumor development involves complex bidirectional interactions between tumor cells and host stromal cells. Endosialin (Tem1) has been identified as a highly O-glycosylated transmembrane glycoprotein, which is specifically expressed by tumor vessel-associated pericytes and stromal fibroblasts of a wide range of human tumors. Recent experiments in endosialin-deficient mice have unraveled a critical role of endosialin in site-specific tumor progression and metastasis. To molecularly understand the mechanisms of endosialin function, we aimed to identify extracellular endosialin ligands and identified Mac-2 BP/90K as a specific interaction partner. Detailed biochemical analyses identified a C-terminal fragment of Mac-2 BP/90K, which was shown to contain binding sites for galectin-3, and collagens as the structures responsible for endosialin binding. Subsequent expression analysis of Mac-2 BP/90K in vivo revealed weak or no expression in most normal tissues and strong up-regulation in tumor cells of human neoplastic tissues. Intriguingly, the expression patterns of Mac-2 BP/90K and endosialin were mutually exclusive in all human tissues. Correspondingly, loss-of-function adhesion experiments of Mac-2 BP/90K-expressing tumor cells on endosialin-expressing fibroblasts revealed a repulsive outcome of the Mac-2 BP/90K interaction. Taken together, the experiments identify a novel repulsive interaction between endosialin on stromal fibroblasts and Mac-2 BP/90K on tumor cells.

Upstream stimulatory factor regulates constitutive expression and hormonal suppression of the 90K (Mac-2BP) protein

We previously reported that hormones important for the normal growth and function of FRTL-5 rat thyroid cells, TSH, or its cAMP signal plus insulin or IGF-I, could transcriptionally suppress constitutive and gamma-interferon (IFN)-increased synthesis of the 90K protein (also known as Mac-2BP). Here we cloned the 5'-flanking region of the rat 90K gene and identified a minimal promoter containing an interferon response element and a consensus E-box or upstream stimulator factor (USF) binding site, which are highly conserved in both the human and murine genes. We show that suppression of constitutive and gamma-IFN-increased 90K gene expression by TSH/cAMP plus insulin/IGF-I depends on the ability of the hormones to decrease the binding of USF to the E-box, located upstream of the interferon response element. This site is required for the constitutive expression of the 90K gene. Transfection with USF1 and USF2 cDNAs increases constitutive promoter activity, attenuates the ability of TSH/cAMP plus insulin/IGF-I to decrease constitutive or gamma-IFN-increased 90K gene expression but does not abrogate the ability of gamma-IFN itself to increase 90K gene expression.

The proteomic analysis of mouse choroid plexus secretome reveals a high protein secretion capacity of choroidal epithelial cells

Choroid plexuses (CP) are involved in multiple functions related to their unique architecture and localization at the interface between the blood and cerebrospinal fluid compartments. These include the release by choroidal epithelial cells (CEC) of biologically active molecules, such as polypeptides, which are distributed globally to the brain. Here, we have used a proteomic approach to get an unbiased overview of the proteins that are secreted by primary cultures enriched in epithelial cells from mice CP. We identified a total of 43 proteins secreted through the classical vesicular pathway in CEC -conditioned medium. They include transport proteins, collagen subunits and other cell matrix proteins, proteases, protease inhibitors and neurotrophic factors. Treating CEC cultures with lipopolysaccharide, increased the secretion of four protein species and induced the release of two additional proteins. Our study also reveals a higher protein secretion capacity of CECs compared with other CP cells or cultured astrocytes. In conclusion, this study provides for the first time the characterization of the major proteins that are secreted by CECs. These proteins may play a critical role in neuronal growth, differentiation and function as well as in brain pathologies.

Tumor-associated antigen 90K/Mac-2-binding protein: possible role in colon cancer

The tumor-associated antigen 90K (TAA90K)/Mac-2-binding protein implicated in cancer progression and metastasis is modified by beta1-6 branched N-linked oligosaccharides in colon cancer cells, glycans shown to contribute to cancer metastasis. To elucidate the role of TAA90K in colon cancer, we examined its expression and function in human colon tumors and colon carcinoma cell lines. Immunohistochemical analyses of colon tumors revealed elevated expression of TAA90K in all samples analyzed compared to normal colon. To examine the function of TAA90K in colon cancer, we carried out protein and cell binding assays using TAA90K-His purified from HT-29 cells colon carcinoma cells infected with recombinant vaccinia virus expressing TAA90K containing a C-terminal poly-histidine tag. TAA90K-His bound to fibronectin, collagen IV, laminins-1, -5, and -10 and galectin-3 (Mac-2) but poorly to collagen I and galectin-1. As expected, binding of TAA90K to galectin-3 was dependent on carbohydrate since it was inhibitable by lactose and asiolofetuin, and a TAA90K-His glycoform purified from HT-29 cells treated with the glycosylation inhibitor 1-deoxymannojirimycin bound poorly to galectin-3. Unlike TAA90K isolated from other cell types, TAA90K-His isolated from colon cancer cells failed to mediate adhesion of colon cancer and normal cell lines, possibly due to cell-type specific glycosylation of TAA90K-His and/or its putative cellular receptor. However, at low concentrations, TAA90K-His enhanced galectin-3-mediated HT-29 cell adhesion while at high concentrations, it inhibited cell adhesion. Thus, a possible mechanism by which TAA90K may contribute to colon cancer progression is by modulating tumor cell adhesion to extracellular proteins, including galectin-3.

Macrophage scavenger receptor down-regulates mycobacterial cord factor-induced proinflammatory cytokine production by alveolar and hepatic macrophages

We aimed to reveal the regulatory function of macrophage scavenger receptor-A (MSR-A) in proinflammatory cytokine production by macrophages stimulated with mycobacterial cord factor (CF). By the culture with CF, MSR-A (+/+) alveolar macrophages and Kupffer cells produced TNF-alpha/MIP-1alpha in a time- and dose-dependent manner. However, the amounts of cytokines produced by them were much less compared to those produced by MSR-A (-/-) macrophages. Consistent with this, treatment of MSR-A (+/+) macrophages with anti-MSR-A antibody increased TNF-alpha production. Binding of CF to MSR-A was demonstrated by measuring the binding affinity. These results indicate that CF binds MSR-A, and MSR-A down-regulates TNF-alpha/MIP-1alpha production by activated macrophages, suggesting the role of this receptor in suppression of excessive inflammatory responses during mycobacterial infection.

Cyclophilin C-associated protein is up-regulated during wound healing

Cyclophilin C-associated protein (CyCAP) is identified from macrophages. It locates in intracellular, membrane bound and extracellular, suggesting it has an important role, however both of its regulation and function have not been elucidated. The expression of CyCAP in skin and during wound healing is also unknown. We demonstrate that CyCAP is expressed in both dermal fibroblasts and keratinocytes. In the dermis, the majority of CyCAP protein is located intracellular in a filamentous protein form while a lesser amount is in the extracellular matrix (ECM). CyCAP gene and protein expression is increased 1 day after skin wound healing in both fetal and adult rats and remains elevated level up to 1 week in adult rats. Immunohistochemistry studies demonstrate that the increased CyCAP expression locates mainly to inflammatory cells, including macrophages, monocytes and lymphocytes during wound healing. Interferon-gamma increases CyCAP gene and protein expression in cultured rat fibroblasts. We also found that wound healing is slower and less collagen is expressed in skin of CyCAP null mice. These data are the first observations of CyCAP expression in skin and during wound repair. Our data indicates that CyCAP is regulated by IFNgamma and may function on immune defense in macrophages, lymphocytes, dermal fibroblasts and keratinocytes during wound healing.

Galectin-3 expression is induced in renal β-intercalated cells during metabolic acidosis

The adaptation of the cortical collecting duct (CCD) to metabolic acidosis requires the polymerization and deposition in the extracellular matrix of the novel protein hensin. HCO3−-secreting β-intercalated cells remove apical Cl−:HCO3−exchangers and may reverse functional polarity to secrete protons. Using intercalated cells in culture, we found that galectin-3 facilitated hensin polymerization, thereby causing their differentiation into the H+-secreting cell phenotype. We examined the expression of galectin-3 in the rabbit kidney and its relationship to hensin during metabolic acidosis. In control kidneys, galectin-3 was expressed in the cortical and medullary collecting ducts. In the outer cortex 26 ± 3% of CCD cells expressed galectin-3 compared with 64 ± 3% of the cells of the inner cortex. In the CCD, galectin-3 was rarely expressed in β-intercalated cells, being primarily present in α-intercalated and principal cells. During metabolic acidosis, the intensity of cellular staining for galectin-3 increased and more cells began to express it; the percentage of CCD cells expressing galectin-3 increased from 26 ± 3 to 66 ± 3% in the outer cortex and from 64 ± 3 to 78 ± 4% in the inner cortex. This was particularly evident in β-intercalated cells where expression was found in only 8 ± 2% in control animals but in 75 ± 2% during metabolic acidosis in the outer cortex and similarly for the inner cortex (26 ± 6 to 90 ± 7%). Importantly, both galectin-3 and hensin were found in the extracellular matrix of microdissected CCDs; and during metabolic acidosis, many more cells exhibited this extracellular colocalization. Thus galectin-3 may play several important roles in the CCD, including mediating the adaptation of β-intercalated cells during metabolic acidosis.

Cyclophilin C-associated protein and cyclophilin C mRNA are upregulated in penumbral neurons and microglia after focal cerebral ischemia

Immunophilin ligands, such as cyclosporin A and FK506, have neuroprotective effects in experimental stroke models, although the precise mechanism is unclear. Cyclophilin C-associated protein (CyCAP) is a natural cellular ligand for the immunophilin, cyclophilin C, and has a protective effect against endotoxins by downmodulating the proinflammatory response. Expressions of CyCAP and cyclophilin C mRNA in a rat middle cerebral artery (MCA) occlusion ischemia model were investigated by Northern blotting and in situ hybridization. Both CyCAP and cyclophilin C mRNAs were ubiquitously distributed in the neurons of the normal brain. Expression increased in neurons of the periinfarct zone up to 7 days after MCA occlusion. The neuronal distribution was confirmed by counterimmunostaining of NeuN. Both mRNAs were predominantly expressed in microglia of the ischemic core at 7 days, confirmed by immunostaining with the microglial marker, ED1. The quantification of CyCAP and cyclophilin C mRNAs at 7 days by Northern blot analysis showed the 8.5-fold increase (P<0.005, n=6) and 6.8-fold increase (P<0.005, n=6), respectively, in ischemic core compared with control. The coincidence of CyCAP and cyclophilin C expression in neurons and microglia suggests distinct roles in each cellular population. In particular, the early increase in penumbral neurons might be related to protection in periinfarct neurons.

Cyclophilin C-associated protein is a mediator for fibronectin fragment-induced matrix metalloproteinase-13 expression

The function of cyclophilin C-associated protein (CyC-AP) on expression of extracellular matrix and matrix metalloproteinases (MMPs) was studied in CyC-AP-null mice. Fibronectin showed increased expression of the 53- and 29-kDa fragments in skin and wounds from CyC-AP-null mice. Type I collagen had an initial degraded pattern in the skin of CyC-AP-null mice, which did not occur in wild-type mice. MMP-3, MMP-13, MMP-14, and tumor necrosis factor-alpha (TNFalpha) had a higher expression in CyC-AP-null skin. During wound healing, MMP-13 and TNFalpha were stimulated to an even higher level, suggesting they are regulated by multiple factors. To understand the regulatory mechanisms of the up-regulated MMPs, the direct effects of TNFalpha, IL-1beta, 45-kDa fibronectin fragment (FN-45), and the 70-kDa fibronectin fragments (FN-70) on the expression of MMPs were studied. MMP-13 expression increased significantly in both CyC-AP-null and wild-type dermal fibroblasts after treatment with IL-1beta or with TNFalpha. However, MMP-13 expression did not increase in CyC-AP-null fibroblasts but did increase only in wild-type fibroblasts after FN-45 and FN-70 treatment. MMP-3 activation was induced by FN-45 and did not show a difference between CyC-AP-null and wild-type fibroblasts, suggesting different regulatory pathways for FN-45 on MMP-13 and MMP-3 expression. Our data are the first to demonstrate that deletion of CyC-AP can abolish fibronectin fragment-induced MMP-13 expression through an unknown mechanism. CyC-AP is an important factor for the regulation of MMP-13 expression.

Human T-cell leukemia virus type 1 Tax protein stimulates the interferon-responsive enhancer element via NF-kappaB activity

Gene expression in Rat-1 fibroblast cells transformed by Tax from human T-cell leukemia virus type 1 was studied using the reverse transcriptase polymerase chain reaction differential display technique. The analysis revealed eight genes that were upregulated and one gene that was suppressed in Tax-transformed cells. Interestingly, at least four of the upregulated genes were interferon-stimulated genes. Promoter analysis of the 2',5'-oligoadenylate synthetase gene, which was activated in both Tax-transformed Rat-1 cells and primary adult T-cell leukemia cells, demonstrated that Tax indirectly activates its interferon-responsive enhancer element in a nuclear factor-kappaB pathway-dependent manner, indicating a close association of interferon signaling with the transformation by Tax.

Integrated genomic and proteomic analysis of signaling pathways in dendritic cell differentiation and maturation

Dendritic cells (DCs) are antigen-presenting cells that play a major role in initiating primary immune responses. Their phenotypic and functional characteristics are intimately linked to their stage of maturation. The specific biochemical pathways and genes whose expression mediates differentiation of progenitors to DCs and their maturation are largely undefined. We recently utilized two approaches, DNA microarrays and proteomics, to analyze the expression profile of human CD14(+) blood monocytes and their derived DCs. Approximately 4% of the genes or proteins expressed were found to be regulated during DC differentiation. Most of these genes were not previously associated with DCs and included genes highly relevant to DC functions (genes involved in antigen presentation, cell adhesion and motility, lipid metabolism). Genes involved in specific signaling pathways, including IkappaBalpha, PPAR-gamma and C/EBPalpha as well as two members of the family of transcription factors, interferon regulatory factors (IRFs), were also modified. Modulation of IRF gene expression is of particular interest because of their functional roles in innate and adaptive immune responses. IRF-family members control the expression of proteins that include type-1 interferons, interleukin-12, interleukin-15, MHC molecules and adhesion molecules. They have also been found to play an important role in lymphocyte development. In contrast to DC differentiation, very few genes were modified at the transcript level during DC maturation as determined by microarray experiments. Further analysis suggested that DC maturation is largely controlled by posttranscriptional and posttranslational modifications. The use of proteomics is therefore necessary for a full comprehension of DC maturation process.

Functional studies on recombinant domains of Mac-2-binding protein

Mac-2-binding protein (M2BP) is a secreted glycoprotein suggested to have a role in host defense. It forms linear and ring-shaped oligomers, with each ring segment being composed of two monomers. We have produced recombinant human M2BP fragments comprising domains 1 and 2 (M2BP-1,2) and domains 3 and 4 (M2BP-3,4) in 293 human kidney cells to characterize structural and functional properties of M2BP. Both fragments were obtained in a native and glycosylated form, as analyzed by CD spectroscopy, trypsin susceptibility, and enzymatic deglycosylation. These results strongly suggest that both fragments are autonomous folding units. All three potential N-glycosylation sites in M2BP-1,2 and all four in M2BP-3,4 were found to be occupied. M2BP-1,2 expressed in tunicamycin-treated cells contained no glycosyl residues, indicating that O-glycosylation is not occurring. Ultracentrifugation revealed that M2BP-1,2 is homogeneously dimeric in the nanomolar range reflecting the properties of intact M2BP. Domain 2 (BTB/POZ domain) is thus identified as the dimerization domain of M2BP, because it has been formerly shown that recombinant domain 1 is monomeric. M2BP-3,4 showed a concentration-dependent self-association, and aggregates of different size and shape were shown by electron microscopy. In contrast to this irregular aggregation of M2BP-3,4, it has been formerly shown that a fragment comprising domains 2-4 still has the ability to form ring-like structures, although the rings are protein-filled, and thus domain 2 appears to be indispensable for ring formation. Solid phase assays showed that M2BP-3,4 contains binding sites for galectin-3, nidogen, and collagens V and VI, whereas M2BP-1,2 is inactive in binding. Both fragments showed no cell adhesive activity in contrast to native M2BP, suggesting that a concerted binding action and/or multivalent interactions of rings are necessary for cell attachment.

Variations in serum IL-7 and 90K/Mac-2 binding protein (Mac-2 BP) levels analysed in cohorts of HIV-1 patients and correlated with clinical changes following antiretroviral therapy

Serum levels of interleukin-7 (IL-7), a non-redundant cytokine that plays a crucial role in lymphopoiesis, are known to be elevated in HIV-1-infected subjects. To examine further the association between levels of IL-7, CD4+ cell counts and viraemia, we analysed these parameters in a large cohort of HIV-1 patients along with serum levels of 90K, a marker of disease severity but with no established involvement in lymphopoiesis. While IL-7 levels were only found to correlate with CD4+ cell counts, 90K levels presented strong correlations with both CD4+ cell numbers and with plasma viral loads (VLs). These correlations were maintained in patients naive to treatment with antiretrovirals (n = 38) but were abolished when the analysis was restricted to the group receiving highly active antiretroviral therapy (HAART, n = 82). Moreover, although 90K levels were significantly reduced in patients on HAART, IL-7 levels continued to be elevated despite successful treatment. The influence of HAART on the variations in these serum parameters was further assessed in a longitudinal study on 32 subjects. The HAART-induced decrease in VLs and increase in CD4+ counts were found to correlate with a reduced serum level of 90K and IL-7, respectively. Nevertheless, following a median period of 33 months of immunological and virological successful HAART, serum levels of IL-7 continued to be significantly elevated compared with those detected in healthy controls. These findings suggest that immunotherapy with IL-7, aimed to replenish T-cell stock in HAART-treated subjects, may have a limited impact on the process of immune reconstitution.

Distinct ligand binding properties of Mac-2-binding protein and mouse cyclophilin [correction of mousephilin] C-associated protein

Human Mac-2-binding protein (Mac-2-BP) is a secreted glycoprotein that is widely expressed. It binds to the human macrophage-associated lectin Mac-2 and has been suggested to have a role in host defence. Mouse cyclophilin C-associated protein (mCyCAP) is also a secreted glycoprotein that binds with high affinity to cyclophilin C in the absence of the immunosuppressive drug cyclosporin A. The two proteins share a similar domain structure and considerable sequence identity, including a highly conserved scavenger receptor cysteine-rich domain, and both of them exert their function within the immune system. To elucidate whether these molecules are also functional homologues, we compared their ligand binding properties using cell lines which express Mac-2-BP or mCyCAP as well as transfected cell lines stably expressing mCyCAP or a mutant version lacking the scavenger domain. These experiments show that Mac-2-BP is unable to bind to either human or mouse cyclophilin C and thatmCyCAP cannot bind to Mac-2. The scavenger domain is not required for the interaction between mCyCAP and cyclophilin C. We conclude that these proteins may be part of a larger family of proteins of immunological importance in which closer functional homologues might exists.

Profiling changes in gene expression during differentiation and maturation of monocyte-derived dendritic cells using both oligonucleotide microarrays and proteomics

Dendritic cells (DCs) are antigen-presenting cells that play a major role in initiating primary immune responses. We have utilized two independent approaches, DNA microarrays and proteomics, to analyze the expression profile of human CD14(+) blood monocytes and their derived DCs. Analysis of gene expression changes at the RNA level using oligonucleotide microarrays complementary to 6300 human genes showed that approximately 40% of the genes were expressed in DCs. A total of 255 genes (4%) were found to be regulated during DC differentiation or maturation. Most of these genes were not previously associated with DCs and included genes encoding secreted proteins as well as genes involved in cell adhesion, signaling, and lipid metabolism. Protein analysis of the same cell populations was done using two-dimensional gel electrophoresis. A total of 900 distinct protein spots were included, and 4% of them exhibited quantitative changes during DC differentiation and maturation. Differentially expressed proteins were identified by mass spectrometry and found to represent proteins with Ca(2+) binding, fatty acid binding, or chaperone activities as well as proteins involved in cell motility. In addition, proteomic analysis provided an assessment of post-translational modifications. The chaperone protein, calreticulin, was found to undergo cleavage, yielding a novel form. The combined oligonucleotide microarray and proteomic approaches have uncovered novel genes associated with DC differentiation and maturation and has allowed analysis of post-translational modifications of specific proteins as part of these processes.

The function of scavenger receptors expressed by macrophages and their role in the regulation of inflammation

Macrophages are able to recognise and internalise apoptotic and foreign cells from the tissue microenvironment and, where pertinent, initiate inflammation and macrophage activation. Regulation of this protective response is important so as to prevent inappropriate activation of host cells and excessive tissue damage. Scavenger receptors (SRs) are widely expressed by macrophages and are able to bind a diverse array of endogenous and foreign molecules. Studies have concentrated on the role of the receptors in atherosclerosis as they can endocytose modified lipoproteins, however, this review will detail the accumulating evidence that SRs function in innate immunity and macrophage control during inflammation.

Isolation, in silico characterization and chromosomal localization of a group of cDNAs from ciliated epithelial cells after in vitro ciliogenesis

BACKGROUND

Immotile cilia syndrome (ICS) or primary ciliary dyskinesia (PCD) is an autosomal recessive disorder in humans in which the beating of cilia and sperm flagella is impaired. Ciliated epithelial cell linings are present in many tissues. To understand ciliary assembly and motility, it is important to isolate those genes involved in the process.

RESULTS

Total RNA was isolated from cultured ciliated nasal epithelial cells after in vitro ciliogenesis and expressed sequenced tags (ESTs) were generated. The functions and locations of 63 of these ESTs were derived by BLAST from two public databases. These ESTs are grouped into various classes. One group has high homology not only with the mitochondrial genome but also with one or more chromosomal DNAs, suggesting that very similar genes, or genes with very similar domains, are expressed from both mitochondrial and nuclear DNA. A second class comprises genes with complete homology with part of a known gene, suggesting that they are the same genes. A third group has partial homology with domains of known genes. A fourth group, constituting 33% of the ESTs characterized, has no significant homology with any gene or EST in the database.

CONCLUSIONS

We have shown that sufficient information about the location of ESTs could be derived electronically from the recently completed human genome sequences. This strategy of EST localization should be significantly useful for mapping and identification of new genes in the forthcoming human genome sequences with the vast number of ESTs in the dbEST database.

Dynamic expression of multiple scavenger receptor cysteine-rich genes in coelomocytes of the purple sea urchin

Coelomocytes, the heterogeneous population of sea urchin putative immune cells, were found to express a complex set of transcripts featuring scavenger receptor cysteine-rich (SRCR) repeats. SRCR domains define a metazoan superfamily of proteins, many of which are implicated in development and regulation of the immune system of vertebrates. Coelomocytes transcribe multiple SRCR genes from among a multigene family encoding an estimated number of 1,200 SRCR domains in specific patterns particular to each individual. Transcription levels for given SRCR genes may range from pronounced to undetectable, yet all tested animals harbor the genomic loci encoding these genes. Analysis of several SRCR genes revealed multiple loci corresponding to each type. In the case of one SRCR type, a cluster of at least three genes was detected within a 133-kb bacterial artificial chromosome insert, and conserved as well as unique regions were identified in sequences of three genomic clones derived from a single animal. Array hybridizations with repeated samples of coelomocyte messages revealed substantial alterations in levels of expression of many SRCR genes, with fluctuations of up to 10-fold in 1 week and up to 30-fold over a period of 3 months. This report is the first demonstration of genomic and transcriptional complexity in molecules expressed by invertebrate coelomocytes. The mechanisms controlling SRCR gene expression and the functional significance of this dynamic system await elucidation.

Monoclonal antibodies specific for human tumor-associated antigen 90K/Mac-2 binding protein: tools to examine protein conformation and function

As part of our effort to identify glycoproteins that contribute to colon cancer progression, we have previously described a family of structurally related glycoproteins expressing beta1-6 branched asparagine(Asn)-linked oligosaccharides defined by monoclonal antibody (MAb 1H9), which are differentially expressed, processed, and glycosylated by human colon carcinoma cell lines (Laferté and Loh [1992]; Biochem J; 283:193-201). MAb 1H9 immunoprecipitates three glycoproteins having apparent sizes of 92-100, 66-70, and 25 kDa, the size heterogeneity attributable to cell-type specific glycosylation differences. We report on the basis of partial protein and cDNA sequence information, that the 100-kDa glycoprotein detected by MAb 1H9 is identical to the 90-kDa glycoprotein variably known as tumor-associated antigen 90K (TAA90K), Mac-2 binding protein, and cyclophilin C-associated protein. Using a PCR-based cloning strategy, the complete cDNA encoding TAA90K was cloned into the eukaryotic expression vector pCDNA-3 (pCD-TAA90K(wt)) and the protein expressed in COS-1 cells. A [(35)S]methionine-labeled 60-kDa polypeptide, processed to an endoglycosidase H-sensitive 74-kDa glycoprotein in the presence of dog pancreas microsomes, was detected in a coupled transcription/translation in vitro reaction. The in vitro-translated 60-kDa polypeptide and N-glycanase-treated TAA90K (60-kDa species) immunoprecipitated from HT29 cells were shown to be structurally identical by limited proteolytic peptide mapping. Using a new panel of 11 TAA90K-specific monoclonal antibodies, including five specific for human TAA90K and six cross-reactive with a 90-kDa species expressed by COS-1 cells, we have detected conformational differences between recombinant wild-type TAA90K, in vitro-synthesized TAA90K, and mutant forms of TAA90K containing point mutations at residues 189, 223, and 259. Furthermore, we have shown that these mutant forms of TAA90K, as well as a truncated form of TAA90K containing amino acid residues 1-383, are defective in secretion. These studies demonstrate the potential usefulness of TAA90K-specific monoclonal antibodies for examining the structure and function of TAA90K, and highlight the contribution of specific amino acid residues to its normal processing and secretion.