CAV1 is a prognostic predictor for patients with idiopathic pulmonary fibrosis and lung cancer

The extremely high mortality of both lung cancer and Idiopathic pulmonary fibrosis (IPF) is a global threat. Early detection and diagnosis can reduce their mortality. Since fibrosis is a necessary process of cancer, identifying the common potential prognostic genes involved in these two diseases will significantly contribute to disease prevention and targeted therapy. Microarray datasets of IPF and lung cancer were extracted from the GEO database. GEO2R was exploited to retrieve the differentially expressed genes (DEGs). The intersecting DEGs were obtained by the Venn tool. DAVID tools were used to perform GO and KEGG pathway enrichment analysis of DEGs. Then, the Kaplan-Meier plotter was employed to determine the prognostic value and verify the expression, pathological stage, and phosphorylation level of the hub gene in the TCGA and GTEx database. Finally, the extent of immune cell infiltration in lung cancer was estimated by the TIMER2 tool. The Venn diagram revealed 1 upregulated gene and 15 downregulated genes from GSE32863, GSE43458, GSE118370, and GSE75037 of lung cancer, as well as GSE2052 and GSE53845 of IPF. CytoHubba identified the top three genes [TEK receptor tyrosine kinase (TEK), caveolin 1 (CAV1), and endomucin (EMCN)] as hub genes following the connectivity degree. Survival analysis claimed the association of only TEK and CAV1 expression to both overall survival (OS) and first progression (FP). Pathological stage analyses revealed the relationship of only CAV1 expression to the pathological stage and the significant correlation of only CAV1 phosphorylation expression level for lung cancer. Furthermore, a statistically positive correlation was observed between the immune infiltration of cancer-associated fibroblasts, endothelial, and neutrophils with the CAV1 expression in lung cancer, whereas the contradictory result was noted for the immune infiltration of T cell follicular helper. Early detection and diagnostic potential of lung cancer are ameliorated by the combined selection of key genes among IPF and lung cancer.

Novel insights into the evolution of the caveolin superfamily and mechanisms of antiapoptotic effects and cell proliferation in lamprey

Caveolin-1 is the main structural and functional component of caveolin, and it is involved in the regulation of cholesterol transport, endocytosis, and signal transduction. Moreover, changes in caveolin-1 play an important role in tumorigenesis and inflammatory processes. Previous studies have demonstrated that human caveolin-1 is mainly located in the cell membrane and exhibits cell type- and stage-dependent functional differences during cancer development and inflammatory responses. However, the role of Lamprey-caveolin-like (L-caveolin-like) in lamprey remained unknown. Here, we demonstrated that L-caveolin-like performs anti-inflammation and oncogenic functions and the function of caveolin-1 diverged during vertebrate evolution. Moreover, the results reveal the mechanism underlying the antiapoptotic effects of L-caveolin-like. An L-caveolin-like gene from Lampetra japonica (L. japonica) was identified and characterized. L-Caveolin-like was primarily distributed in the leukocytes, intestines and supraneural bodies (Sp-bodies) immune organs as indicated by Q-PCR and immunohistochemistry assays. The mRNA and protein expression levels of L-caveolin exhibited consistent increases in expression at 2 and 72 h in adult tissues after exposure to lipopolysaccharide (LPS) and in leukocytes stimulated by Vibrio anguillarum (V. anguillarum), Staphylococcus aureus (S. aureus), and Poly I:C. Furthermore, the overexpression of pEGFP-N1-L-caveolin-like was associated with a distinct localization in mitochondria, with decreased cytochrome C (Cyt C) and mitochondrial Cyt C oxidase subunit I (CO I) expression. In addition, increased cellular ATP levels suggested that this protein prevented mitochondrial damage. The overexpression of pEGFP-N1-L-caveolin-like led to the altered expression of factors related to apoptosis, such as decreased Caspase-9, Caspase-3, p53, and Bax expression and increased Bcl-2 expression. In addition, the overexpression of pEGFP-N1-L-caveolin-like promoted cell proliferation associated with upregulated EGF, bFGF, and PDGFB expression. Together, these findings indicated that the L-caveolin-like protein from L. japonica induced the activation of antiapoptotic effects via the mitochondrial Cyt C-mediated Caspase-3 signaling pathway. Our analysis further suggests that L-caveolin-like is an oncogene protein product and anti-inflammatory molecule from lamprey that evolved early in vertebrate evolution.

CD14 Is a Co-Receptor for TLR4 in the S100A9-Induced Pro-Inflammatory Response in Monocytes

The cytosolic Ca²⁺-binding S100A9 and S100A8 proteins form heterodimers that are primarily expressed in human neutrophils and monocytes. We have recently shown that S100A9 binds to TLR4 in vitro and induces TLR4-dependent NF-κB activation and a pro-inflammatory cytokine response in monocytes. In the present report we have further investigated the S100A9-mediated stimulation of TLR4 in monocytes. Using transmission immunoelectron microscopy, we detected focal binding of S100A9 to monocyte membrane subdomains containing the caveolin-1 protein and TLR4. Furthermore, the S100A9 protein was detected in early endosomes of the stimulated cells, indicating that the protein could be internalized by endocytosis. Although stimulation of monocytes with S100A9 was strictly TLR4-dependent, binding of S100A9 to the plasma membrane and endocytosis of S100A9 was still detectable and coincided with CD14 expression in TLR4-deficient cells. We therefore investigated whether CD14 would be involved in the TLR4-dependent stimulation and could show that the S100A9-induced cytokine response was inhibited both in CD14-deficient cells and in cells exposed to CD14 blocking antibodies. Further, S100A9 was not internalized into CD14-deficient cells suggesting a direct role of CD14 in endocytosis of S100A9. Finally, we could detect satiable binding of S100A9 to CD14 in surface plasmon resonance experiments. Taken together, these results indicate that CD14 is a co-receptor of TLR4 in the S100A9-induced cytokine response.

A Cysteine Zipper Stabilizes a Pre-Fusion F Glycoprotein Vaccine for Respiratory Syncytial Virus

Recombinant subunit vaccines should contain minimal non-pathogen motifs to reduce potential off-target reactivity. We recently developed a vaccine antigen against respiratory syncytial virus (RSV), which comprised the fusion (F) glycoprotein stabilized in its pre-fusion trimeric conformation by "DS-Cav1" mutations and by an appended C-terminal trimerization motif or "foldon" from T4-bacteriophage fibritin. Here we investigate the creation of a cysteine zipper to allow for the removal of the phage foldon, while maintaining the immunogenicity of the parent DS-Cav1+foldon antigen. Constructs without foldon yielded RSV F monomers, and enzymatic removal of the phage foldon from pre-fusion F trimers resulted in their dissociation into monomers. Because the native C terminus of the pre-fusion RSV F ectodomain encompasses a viral trimeric coiled-coil, we explored whether introduction of cysteine residues capable of forming inter-protomer disulfides might allow for stable trimers. Structural modeling indicated the introduced cysteines to form disulfide "rings", with each ring comprising a different set of inward facing residues of the coiled-coil. Three sets of rings could be placed within the native RSV F coiled-coil, and additional rings could be added by duplicating portions of the coiled-coil. High levels of neutralizing activity in mice, equivalent to that of the parent DS-Cav1+foldon antigen, were elicited by a 4-ring stabilized RSV F trimer with no foldon. Structure-based alteration of a viral coiled-coil to create a cysteine zipper thus allows a phage trimerization motif to be removed from a candidate vaccine antigen.

Inhibition of caveolin-1 restores myeloid cell function in human glioblastoma

Background

Gliomas are the most common primary brain tumor in both children and adults. The prognosis for glioblastoma (GBM), the most common type of malignant glioma, has remained dismal, with median survival a little over one year despite maximal therapy with surgery, chemotherapy, and radiation. Although immunotherapy has become increasingly successful against many systemic tumors, clinical efficacy against brain tumors has been limited. One reason for this is an incomplete understanding of the local immunologic tumor microenvironment, particularly the function of large numbers of infiltrating myeloid derived cells. Monocytes/microglia are myeloid derived immunomodulatory cells, and they represent the predominant infiltrating immune cell population in gliomas. Our group has previously demonstrated using complementary invitro and invivo approaches that GBM tumor cells polarize tumor-associated myeloid cells (TAMs) and suppress their immunostimulatory function.

Methods and Results

To better understand the mechanisms responsible for this immunosuppression, we used gene expression profiling of stimulated monocytes in the presence or absence of GBM tumor cells. Our analysis identified caveolin-1 (CAV1), a plasma membrane molecule with pleiotropic functions, as significantly up-regulated in monocytes in the presence of GBMs. We validated these findings exvivo by confirming up-regulation of CAV1 in TAMs isolated from GBMs immediately after surgical resection. Finally, we demonstrate that siRNA inhibition of CAV1 restores myeloid cell function, as measured by TNF-alpha secretion, in the presence of GBMs.

Conclusions

Restoration of TAM function through pharmacologic blockage of CAV1 may facilitate more successful immunotherapeutic strategies directed against a variety of solid human tumors infiltrated by TAMs.

Palmitoylation of MICA, a ligand for NKG2D, mediates its recruitment to membrane microdomains and promotes its shedding

MICA and MICB (MHC-class-I-related chain A/B) are transmembrane proteins expressed in pathological conditions that are ligands for NKG2D, an activating receptor found on cytotoxic lymphocytes. The recognition on target cells of NKG2D ligands leads to the activation of lysis and cytokine secretion by NK cells and T cells. Besides being expressed at the cell surface, MICA/B can be released as soluble proteins. Soluble NKG2D ligands downmodulate expression of the NKG2D receptor on lymphocytes, leading to a diminished cytotoxic response. Prior studies suggested that recruitment of MICA/B molecules to cholesterol-enriched microdomains was an important factor regulating the proteolytic release of these molecules. We now show that recruitment of MICA to these microdomains depends on palmitoylation of two cysteine residues that allow MICA molecules to reside in the membrane in the same domains as caveolin-1. Compared with WT molecules, nonpalmitoylated mutant MICA molecules were shed to the supernatant with low efficiency; however, both WT and mutant MICA were able to trigger NK cell cytotoxicity. These data suggest that the presence of NKG2D ligands at the plasma membrane is sufficient to activate cytotoxicity and reflect the need of different ligands to exploit different cellular pathways to reach the cell surface upon different stress situations.

[Role of caveolin-1 on membrane estrogen receptor mediated proliferation of endothelial progenitor cells]

OBJECTIVE

To investigate the potential role of caveolin-1 (CAV-1) on membrane estrogen receptor (mER) mediated proliferation of endothelial progenitor cells (EPCs).

METHODS

Bone marrow (BM)-derived EPCs were cultured. The proliferation of EPCs induced by estradiol (E₂)-BSA in the absence or presence of ICI 182, 780 (a pure ER inhibitor), MβCD and CAV-1 siRNA was determined by [³H]-thymidine incorporation. The expression of CAV-1 was detected by Western blot.

RESULTS

Proliferation of EPC peaked after 10(-8) mol/L E₂-BSA culture for 24 h (87.5% increase vs. control), and this effect could be inhibited by estrogen receptor blocker ICI 182, 780, indicating that mER-initiated membrane signaling pathways was involved in the proliferation effect of estrogen on EPC. Both cholesterol depletion and CAV-1 siRNA significantly attenuated E₂-BSA induced [³H]-thymidine incorporation. Western blot result confirmed that cholesterol depletion or CAV-1 siRNA significantly decreased CAV-1 protein expression (-18.6% or -41.2% vs. 10(-8) mol/L E₂-BSA alone).

CONCLUSION

Our results suggested that estradiol promoted EPC proliferation through activating CAV-1 pathway.

Double-label immunoelectron microscopy for studying the colocalization of proteins in cultured cells

Multiple label immunoelectron microscopy localizes and detects multiple antigens in cells and tissues. In double labeling, two kinds of primary antibodies from different animal species are used after being mixed in a single solution. To distinguish the different antigens, secondary antibodies should be labeled with colloidal gold particles of different diameter. Generally, the secondary antibody that is used for detecting the antigen with lower distribution density is labeled with smaller-sized gold particles. In this chapter, double-label immunoelectron microscopy of gelatin-embedded cultured cells using the cryosectioning technique is described.

Improved antigen retrieval in freeze-fracture cytochemistry by evaporation of carbon as first replication layer

The recently developed freeze-fracture replica immunolabeling technique uses sodium dodecyl sulfate to clean replicas obtained from chemically unfixed, rapidly frozen cells by evaporation of platinum as first and carbon as second replication layer. The detergent dissolves remains of cellular material with the exception of components which are in direct contact to the replica film. Membrane lipids and membrane protein complexes of the protoplasmic and the exoplasmic membrane halves remain attached to the replica film and are accessible for cytochemical localization. We immunolabeled the membrane proteins caveolin-1 and connexin 43 in mouse cell lines as well as the membrane attached protein tetrachloroethene reductive dehalogenase (PceA) in bacterial cells at freeze-fracture replicas generated by different evaporation parameters. The labeling experiments for caveolin-1 and the PceA showed that freeze-fracture replication of cellular membranes accomplished with thin platinum layers as well as replication with carbon as first evaporation layer lead in these cases to an improved antigen retrieval, whereas the labeling efficiency of connexin 43 was not affected by different evaporation conditions.

Oxygen alters caveolin-1 and nitric oxide synthase-3 functions in ovine fetal and neonatal lung microvascular endothelial cells

We determined the effect of oxygen [∼100 Torr (normoxia) and ∼30–40 Torr (hypoxia)] on functions of endothelial nitric oxide (NO) synthase (NOS-3) and its negative regulator caveolin-1 in ovine fetal and neonatal lung microvascular endothelial cells (MVECs). Fetal NOS-3 activity, measured as NO production with 0.5–0.9 μM 4-amino-5-methylamino-2,7-difluorofluorescein, was decreased in hypoxia by 14.4% ( P < 0.01), inhibitable by the NOS inhibitor N-nitro-l-arginine, and dependent on extracellular arginine. Caveolar function, assessed as FITC-BSA (160 μg/ml) endocytosis, was decreased in hypoxia by 13.5% in fetal and 22.8% in neonatal MVECs ( P < 0.01). NOS-3 and caveolin-1 were physically associated, as demonstrated by coimmunoprecipitation and colocalization, and functionally associated, as shown by cross-activation of endocytosis, by their specific antibodies and activation of NOS by albumin. Caveolin peptide, containing the sequence for the PKC phosphorylation site of caveolin, and caveolin antiserum against the site increased NO production and endocytosis by 12.3% ( P < 0.05) and 16% ( P < 0.05), respectively, in normoxia and increased endocytosis by 25% ( P < 0.001) in hypoxia. PMA decreased NO production in normoxia and hypoxia by 19.32% ( P < 0.001) and 11.8% ( P < 0.001) and decreased endocytosis in normoxia by 20.35% ( P < 0.001). PKC kinase activity was oxygen sensitive, and threonine phosphorylation was enhanced in hypoxia. Pertussis toxin increased caveolar and NOS functions. These data support our hypothesis that increased Po2at birth promotes dissociation of caveolin-1 and NOS-3, with an increase in their activities, and that PKC and an oxygen-sensitive cell surface G protein-coupled receptor regulate caveolin-1 and NOS-3 interactions in fetal and neonatal lung MVECs.

T-cell activation via CD26 and caveolin-1 in rheumatoid synovium

CD26 is a T-cell costimulatory molecule with dipeptidyl peptidase IV (DPPIV) activity in its extracellular region. We previously reported that recombinant soluble CD26 enhances peripheral blood T-cell proliferation induced by the recall antigen tetanus toxoid (TT). Recently, we demonstrated that CD26 binds caveolin-1 on antigen-presenting cell (APC), and that residues 201–211 of CD26 along with the serine catalytic site at residue 630, which constitute a pocket structure of CD26/DPPIV, contribute to binding to caveolin-1 scaffolding domain. In addition, following CD26–caveolin-1 interaction on TT-loaded monocytes, caveolin-1 is phosphorylated, with linkage to NF-κB activation, followed by upregulation of CD86. Finally, reduced caveolin-1 expression on APC inhibits CD26-mediated CD86 upregulation and abrogates CD26 effect on TT-induced T-cell proliferation, and immunohistochemical studies revealed an infiltration of CD26+ T cells in the sublining region of rheumatoid synovium and high expression of caveolin-1 in the increased vasculature and synoviocytes of the rheumatoid synovium. Taken together, these results strongly suggest that CD26–cavolin-1 interaction plays a role in the upregulation of CD86 on TT-loaded APC and subsequent engagement with CD28 on T cells, leading to antigen-specific T-cell activation such as the T-cell-mediated antigen-specific response in rheumatoid arthritis.

Immunohistochemical study of caveolin-1 and -2 in the rat retina

The expression of caveolin-1 and -2 in the retina was examined; Western blot analysis showed that both were present. Immunohistochemistry indicated that caveolin-1 was expressed in the majority of retinal layers, including the ganglion cell layer, inner plexiform layer, outer plexiform layer, and in the vascular endothelial cells of the retina. Caveolin-2 was primarily immunostained in the vessels, but in a few other elements as well. This is the first demonstration of caveolin differential expression in the retina of rats, and suggests that caveolin plays an important role in signal transduction in glial cells and neuronal cells.

Stromal antiapoptotic paracrine loop in perineural invasion of prostatic carcinoma

Caveolin-1 (cav-1) is a major scaffolding component of cell membrane invaginations (caveolae). It is involved in sequestering numerous effectors and signaling molecules and has antiapototic activities in prostate cancer. Perineural invasion (PNI) is associated with decreased apoptosis of cancer cells both in human tissues and the in vitro PNI model. We show here that stromal (perineurium) production of cav-1 is involved in a paracrine antiapoptotic loop in PNI. Transforming growth factor-beta1 is up-regulated in the cancer cells as they approach the nerve and is thought to up-regulate cav-1 in the perineurium of nerves with prostate cancer. Cav-1 is then secreted into the microenvironment and used by prostate cancer cells to inhibit apoptosis. In the in vitro PNI model, this phenomenon is partially reversed by neutralizing cav-1 antibodies or using ganglia from cav-1 knockout mice. Our results show a novel paracrine mechanism used by the prostate cancer in PNI to increase their proliferative activity and decrease apoptosis.