Biochemical and Physical Characterisation of Urinary Nanovesicles following CHAPS Treatment

<div><p>Urinary exosomes represent a precious source of potential biomarkers for disease biology. Currently, the methods for vesicle isolation are severely restricted by the tendency of vesicle entrapment, <em>e.g.</em> by the abundant Tamm-Horsfall protein (THP) polymers. Treatment by reducing agents such as dithiothreitol (DTT) releases entrapped vesicles, thus increasing the final yield. However, this harsh treatment can cause remodelling of all those proteins which feature extra-vesicular domains stabilized by internal disulfide bridges and have detrimental effects on their biological activity. In order to optimize exosomal yield, we explore two vesicle treatment protocols - dithiothreitol (DTT) and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic (CHAPS) - applied to the differential centrifugation protocol for exosomal vesicle isolation. The results show that CHAPS treatment does not affect vesicle morphology or exosomal marker distribution, thus eliminating most of THP interference. Moreover, the recovery and preservation of catalytic activity of two trans-membrane proteases, dipeptidyl peptidase IV and nephrilysin, was examined and found to be clearly superior after CHAPS treatment compared to DTT. Finally, proteomic profiling by mass spectrometry (MS) revealed that 76.2% of proteins recovered by CHAPS are common to those seen for DTT treatment, which illustrates underlining similarities between the two approaches. In conclusion, we provide a major improvement to currently-utilized urinary vesicle isolation strategies to allow recovery of urinary vesicles without the deleterious interference of abundant urinary proteins, while preserving typical protein folding and, consequently, the precious biological activity of urinary proteins which serve as valuable biomarkers.</p> </div

Western blotting analysis.

<p>Rabbit anti-CD63, Rabbit anti-TSG101, rabbit anti-MGF-E8/lactadherin and rabbit anti-nephrin <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037279#pone.0037279-Hara1" target="_blank">[18]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037279#pone.0037279-Khatua1" target="_blank">[50]</a>. Ten µg of protein of fractions obtained in Method 1 were loaded on the gels.</p

Proteases activity.

<p>Membrane-bound DPP IV (Panel A) and NEP (Panel C) peptidase activity profiles recorded in absence and presence of 10 mM DTT. Samples were dialysed at a MWCO of 300 kDa. DTT pellet 200,000 g (sample 1), DTT SN 200,000 g (sample 3), CHAPS pellet 200,000 g (sample 2) and CHAPS SN 200,000 g (sample 4) are represented. Columns compare DTT vs CHAPS after dialysis with a membrane of MWCO 300 kDa and in the presence of 5 mM DTT. Values represent mean ± SD of units of peptidase (UP) per milligram of protein per minute. Panel B represents the Coomassie gel and DDP immunodetection of the same samples. Ten µg of protein per fraction obtained in Method 1 were loaded on the gels after 300 kDa MWCO dialysis.</p

SDS-PAGE.

<p><b>Panel A:</b> Gel Acrylamide T 12% constant. Fifteen µg of protein per lane of crude preparation <b>Panel B:</b> Gel Acrylamide T 8% constant. Ten µg of protein per fraction obtained in Method 1. <b>Panel C:</b> Gel Acrylamide T 12% constant. Ten µg of protein per fraction obtained in Method 2.</p

FhTeg binding to dendritic cells is mediated by MR and is carbohydrate and calcium dependent.

<p><b>A-B:</b> MR-transfected CHO cells (A) and BMDCs (B) were stimulated with and without inhibitors, i.e. EGTA (10mM), anti-MR (1 μg ml^-1), mannan (A: 100 μg ml^-1;B: 1 mg/mL), GalNAc-4S (A: 1mM; B: 25 mM), for 45 min prior to stimulation with fluorescently labelled FhTeg (A: 1–10 μg ml^-1; B: 5 μg/mL) for 45 min. Fluorescently labelled BSA was also used as control. FhTeg binding to cells was assessed by flow cytometry and reported in bar chart format. Data shown is the mean ± SD of one representative experiment; the experiment was repeated 2–3 times, **, <i>p</i> ≤ 0.01; ***, <i>p</i> ≤ 0.001 compared to FhTeg. <b>C-D:</b> BMDCs were stimulated with fluorescently labelled FhTeg (10μg ml^-1, green) or BSA (<u>10g</u> ml^-1, green)) for 45 min prior to paraformaldehyde fixation and mounting with DAPI (blue); Scale bar: 25μm.</p

FhTeg preparation is rich in oligomannose and truncated complex type <i>N-</i>glycans carrying fucose or sulfate/phosphate moieties.

<p>Fh tegumental antigens were digested with trypsin followed by PNGase F treatment. Released N-glycans were subsequently labelled with 2-AA and analysed by MALDI-TOF-MS in the negative ion-reflector mode. Signals are labelled with monoisotopic masses. Most abundant <i>N</i>-glycan structures are annotated in the spectrum while minor peaks are reported in the supplementing material (<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0004601#pntd.0004601.s004" target="_blank">S1 Table</a>). The signal at <i>m/z</i> 1582.8 [M-H]^- is annotated according to MALDI-TOF/TOF-MS analysis.</p

<i>Fasciola hepatica</i> Surface Coat Glycoproteins Contain Mannosylated and Phosphorylated N-glycans and Exhibit Immune Modulatory Properties Independent of the Mannose Receptor

<div><p>Fascioliasis, caused by the liver fluke <i>Fasciola hepatica</i>, is a neglected tropical disease infecting over 1 million individuals annually with 17 million people at risk of infection. Like other helminths, <i>F</i>. <i>hepatica</i> employs mechanisms of immune suppression in order to evade its host immune system. In this study the N-glycosylation of <i>F</i>. <i>hepatica’s</i> tegumental coat (FhTeg) and its carbohydrate-dependent interactions with bone marrow derived dendritic cells (BMDCs) were investigated. Mass spectrometric analysis demonstrated that FhTeg N-glycans comprised mainly of oligomannose and to a lesser extent truncated and complex type glycans, including a phosphorylated subset. The interaction of FhTeg with the mannose receptor (MR) was investigated. Binding of FhTeg to MR-transfected CHO cells and BMDCs was blocked when pre-incubated with mannan. We further elucidated the role played by MR in the immunomodulatory mechanism of FhTeg and demonstrated that while FhTeg’s binding was significantly reduced in BMDCs generated from MR knockout mice, the absence of MR did not alter FhTeg’s ability to induce SOCS3 or suppress cytokine secretion from LPS activated BMDCs. A panel of negatively charged monosaccharides (i.e. GlcNAc-4P, Man-6P and GalNAc-4S) were used in an attempt to inhibit the immunoregulatory properties of phosphorylated oligosaccharides. Notably, GalNAc-4S, a known inhibitor of the Cys-domain of MR, efficiently suppressed FhTeg binding to BMDCs and inhibited the expression of suppressor of cytokine signalling (SOCS) 3, a negative regulator the TLR and STAT3 pathway. We conclude that <i>F</i>. <i>hepatica</i> contains high levels of mannose residues and phosphorylated glycoproteins that are crucial in modulating its host’s immune system, however the role played by MR appears to be limited to the initial binding event suggesting that other C-type lectin receptors are involved in the immunomodulatory mechanism of FhTeg.</p></div