Identification of staphylococcal lipoteichoic acid-binding proteins in human serum by high-resolution LTQ-Orbitrap mass spectrometry

Prohibitin ligands: a growing armamentarium to tackle cancers, osteoporosis, inflammatory, cardiac and neurological diseases

Over the last three decades, the scaffold proteins prohibitins-1 and -2 (PHB1/2) have emerged as key signaling proteins regulating a myriad of signaling pathways in health and diseases. Small molecules targeting PHBs display promising effects against cancers, osteoporosis, inflammatory, cardiac and neurodegenerative diseases. This review provides an updated overview of the various classes of PHB ligands, with an emphasis on their mechanism of action and therapeutic potential. We also describe how these ligands have been used to explore PHB signaling in different physiological and pathological settings.

Staphylococcus epidermidis lipoteichoic acid: exocellular release and ltaS gene expression in clinical and commensal isolates

PURPOSE

Staphylococcus epidermidis ATCC12228 lipoteichoic acid (LTA) inhibits TNFα production from keratinocytes that are activated with poly I:C. However, this effect has not been proven in clinical or commensal isolates.

METHODOLOGY

The <10 kDa fractions of S. epidermidis isolates from ocular infections (n=56), healthy skin (n=35) and healthy conjunctiva (n=32) were obtained. TNFα production was determined by elisa in HaCaT keratinocytes stimulated with poly I:C and with the <10 kDa fractions. LTA in the cytoplasmic membrane and in the <10 kDa fractions of the isolates was determined during bacterial growth by flow cytometry, Western blot and electrospray ionization mass spectrometry. The expression levels of ugtP, ltaA and ltaS were evaluated.

RESULTS

Two populations of isolates were found: a population that inhibited TNFα production (TNFα-inhibitor isolates) and a population that did not inhibit it (TNFα non-inhibitor isolates). The cells from the TNFα-inhibitor isolates had less LTA in the cytoplasmic membrane compared to the cells from the TNFα non-inhibitor isolates (P<0.05). Similarly, LTA was detected in the supernatants of TNFα-inhibitor isolates, and it was absent in TNFα non-inhibitor isolates. High expression levels of the ugtP and ltaA genes in the 1850I (TNFα-inhibitor isolate) and 37HS (TNFα non-inhibitor isolate) isolates were found during bacterial growth. However, the ltaS gene had a low expression level (P<0.05) in the 37HS isolate.

CONCLUSION

The TNFα-inhibitor isolates release LTA due to high expression of the LTA synthesis genes. By contrast, TNFα non-inhibitor isolates do not release LTA due to low expression level of the ltaS gene.

Anti-angiogenic nanotherapy via active targeting systems to tumors and adipose tissue vasculature

Sophisticated drug delivery systems (DDS) are required for delivering drugs, especially macromolecules such as nucleic acids or proteins, to their sites of action. Therefore it is a prerequisite that future DDS are designed to selectively target a tissue. In this review, we focus on systems that actively target the vasculature in tumors or adipose tissues. For targeting tumor vasculatur, a new strategy referred to as dual-targeting is proposed that uses a combination of a receptor specific ligand and a cell penetrating peptide, which can induce the synergistic enhancement of tissue selectivity under in vivo conditions. A novel pH-sensitive cationic lipid was designed to enhance the endosomal release of encapsulated compounds such as siRNA as well as to improve the stability in blood circulation after intravenous administration. A cyclic RGD peptide is used as an active targeting ligand. For targeting adipose vasculature, prohibitin, which is expressed on the surface of adipose endothelial cells, was targeted with KGGRAKD peptides on the surface of PEGylated nanoparticles. Prohibitin targeted nanoparticles (PTNP) encapsulating Cytochrome c (CytC) can selectively target adipose vasculature by optimizing the lengths of the PEG linkers and can deliver CytC to adipose endothelial cells. PTNP can successfully induce anti-obese effects as well as apoptosis by delivering CytC to the cytosol in endothelial cells. Unexpectedly, the EPR (enhanced permeability and retention) effect, which is usually observed in tumor tissue, was also observed in the adipose vasculature, especially in obese mice, where PEGylated nanoparticles can pass through the endothelial barriers in adipose tissue. We believe that these achievements in active targeting will allow a greatly expanded use of DDS for nanomedicines.

Human salivary proteins with affinity to lipoteichoic acid of Enterococcus faecalis

Enterococcus faecalis is associated with refractory apical periodontitis and its lipoteichoic acid (Ef.LTA) is considered as a major virulence factor. Although the binding proteins of Ef.LTA may play an important role for mediating infection and immunity in the oral cavity, little is known about Ef.LTA-binding proteins (Ef.LTA-BPs) in saliva. In this study, we identified salivary Ef.LTA-BPs with biotinylated Ef.LTA (Ef.LTA-biotin) through mass spectrometry. The biotinylation of Ef.LTA was confirmed by binding capacity with streptavidin-FITC on CHO/CD14/TLR2 cells. The biological activity of Ef.LTA-biotin was determined based on the induction of nitric oxide and macrophage inflammatory protein-1α in a macrophage cell-line, RAW 264.7. To identify salivary Ef.LTA-BPs, the Ef.LTA-biotin was mixed with a pool of human saliva obtained from nine healthy subjects followed by precipitation with a streptavidin-coated bead. Ef.LTA-BPs were then separated with 12% SDS-PAGE and subjected to the mass spectrometry. Six human salivary Ef.LTA-BPs including short palate lung and nasal epithelium carcinoma-associated protein 2, zymogen granule protein 16 homolog B, hemoglobin subunit α and β, apolipoprotein A-I, and lipocalin-1 were identified with statistical significance (P<0.05). Ef.LTA-BPs were validated with lipocalin-1 using pull-down assay. Hemoglobin inhibited the biofilm formation of E. faecalis whereas lipocalin-1 did not show such effect. Collectively, the identified Ef.LTA-BPs could provide clues for our understanding of the pathogenesis of E. faecalis and host immunity in oral cavity.

Characterization of Prohibitin 1 as a Host Partner of Vibrio vulnificus RtxA1 Toxin

RtxA1 toxin, which results in cytoskeletal rearrangement, contact cytotoxicity, hemolysis, tissue invasion, and lethality in mice, is the most potent cytotoxic virulence factor of Vibrio vulnificus. Bioinformatics analysis of rtxA1 predicted 4 functional domains that presumably performed discrete functions during host cell killing. V. vulnificus RtxA1 has a unique domain designated as RtxA1-D2, corresponding to amino acids 1951-2574, which is absent in Vibrio cholerae multifunctional-autoprocessing repeats-in-toxin, suggesting that this domain confers specific biological functions to V. vulnificus RtxA1. HeLa cells expressing green fluorescent protein-RtxA1-D2 became round and lost their viability. A yeast 2-hybrid system identified prohibitin (PHB) 1 as the host partner of RtxA1-D2. The specific interaction of RtxA1-D2 with PHB1 was confirmed by performing immunoprecipitation. Interestingly, V. vulnificus RtxA1 up-regulated PHB1 expression on the cytoplasmic membrane of host cells. Extracellular signal-regulated kinase and p38 mitogen-activated protein kinase pathways were confirmed as being important in the up-regulation of PHB1 by using inhibitors. Down-regulation of PHB1 by small interfering RNAs decreased the cytotoxicity of RtxA1-D2 against HeLa cells. The pretreatment of an anti-PHB1 antibody impaired the cytotoxicity of V. vulnificus RtxA1. These results suggest that the involvement PHB1 in the RtxA1 cytotoxicity has significant implications for the pathogenesis of V. vulnificus infections.

HMGB1 Binds to Lipoteichoic Acid and Enhances TNF-α and IL-6 Production through HMGB1-Mediated Transfer of Lipoteichoic Acid to CD14 and TLR2

Lipoteichoic acid (LTA) is a component of the cell wall of Gram-positive bacteria and induces a toll-like receptor 2 (TLR2)-mediated inflammatory response upon initial binding to lipopolysaccharide-binding protein (LBP) and subsequent transfer to CD14. In this study, we identified a novel role for the nuclear protein high-mobility group box 1 (HMGB1) in LTA-mediated inflammation. Results of ELISA, surface plasmon resonance and native PAGE electrophoretic mobility shift analyses indicated that HMGB1 binds to LTA in a concentration-dependent manner and that this binding is inhibited by LBP. Native PAGE, fluorescence-based transfer and confocal imaging analyses indicated that HMGB1 catalytically disaggregates LTA and transfers LTA to CD14. NF-κB p65 nuclear transmigration, degradation of IκBα and reporter assay results demonstrated that NF-κB activity in HEK293-hTLR2/6 cells is significantly upregulated by a mixture of LTA and soluble CD14 in the presence of HMGB1. Furthermore, the production of TNF-α and IL-6 in J774A.1 and RAW264.7 cells increased significantly following treatment with a mixture of LTA and HMGB1 compared with treatment with LTA or HMGB1 alone. Thus, we propose that HMGB1 plays an important role in LTA-mediated inflammation by binding to and transferring LTA to CD14, which is subsequently transferred to TLR2 to induce an inflammatory response.

Identification and quantification of adducts between oxidized rosmarinic acid and thiol compounds by UHPLC-LTQ-Orbitrap and MALDI-TOF/TOF tandem mass spectrometry

LTQ Orbitrap MS/MS was used to identify the adducts between quinones derived from rosmarinic acid (RosA) and thiol compounds, including cysteine (Cys), glutathione (GSH), and peptides digested from myosin. Two adducts of quinone-RosA/Cys and quinone-RosA/2Cys, one quinone-RosA/GSH adduct, and three quinone-RosA/peptide adducts were identified by extracted ion and MS(2) fragment ion chromatograms. By using MALDI-TOF/TOF MS, the adduction reaction between RosA and myosin in myofibrillar protein isolates was determined, demonstrating that the accurate reaction site was at Cys949 of myosin. The effect of reaction conditions, including stirring time, temperature, and oxidative stress, on the formation of adducts was further investigated. The formation of quinone-RosA/Cys and quinone-RosA/GSH increased with stirring time. Both adducts increased with temperature, whereas the reactivity of the addition reaction of GSH was higher than that of Cys. With increasing oxidation stress, the formation of quinone-RosA/GSH adduct increased and that of quinone-RosA/Cys adduct decreased.

Prohibitin ligands in cell death and survival: mode of action and therapeutic potential

Prohibitins (PHBs) are scaffold proteins that modulate many signaling pathways controlling cell survival, metabolism, and inflammation. Several drugs that target PHBs have been identified and evaluated for various clinical applications. Preclinical and clinical studies indicate that these PHB ligands may be useful in oncology, cardiology, and neurology, as well as against obesity. This review covers the physiological role of PHBs in health and diseases and current developments concerning PHB ligands.