38 research outputs found
Solution structure of a repeated unit of the ABA-1 nematode polyprotein allergen of ascaris reveals a novel fold and two discrete lipid-binding sites
Parasitic nematode worms cause serious health problems in humans and other animals. They can induce allergic-type immune responses, which can be harmful but may at the same time protect against the infections. Allergens are proteins that trigger allergic reactions and these parasites produce a type that is confined to nematodes, the nematode polyprotein allergens (NPAs). These are synthesized as large precursor proteins comprising repeating units of similar amino acid sequence that are subsequently cleaved into multiple copies of the allergen protein. NPAs bind small lipids such as fatty acids and retinol (Vitamin A) and probably transport these sensitive and insoluble compounds between the tissues of the worms. Nematodes cannot synthesize these lipids, so NPAs may also be crucial for extracting nutrients from their hosts. They may also be involved in altering immune responses by controlling the lipids by which the immune and inflammatory cells communicate. We describe the molecular structure of one unit of an NPA, the well-known ABA-1 allergen of Ascaris and find its structure to be of a type not previously found for lipid-binding proteins, and we describe the unusual sites where lipids bind within this structur
The Protease Inhibitor Alpha-2-Macroglobuline-Like-1 Is the p170 Antigen Recognized by Paraneoplastic Pemphigus Autoantibodies in Human
Paraneoplastic pemphigus (PNP) is a devastating autoimmune blistering disease, involving mucocutaneous and internal organs, and associated with underlying neoplasms. PNP is characterized by the production of autoantibodies targeting proteins of the plakin and cadherin families involved in maintenance of cell architecture and tissue cohesion. Nevertheless, the identity of an antigen of Mr 170,000 (p170), thought to be critical in PNP pathogenesis, has remained unknown
Folic Acid Exposure Rescues Spina Bifida Aperta Phenotypes in Human Induced Pluripotent Stem Cell Model
Neural tube defects (NTDs) are severe congenital abnormalities, caused by failed closure of neural tube during early embryonic development. Periconceptional folic acid (FA) supplementation greatly reduces the risk of NTDs. However, the molecular mechanisms behind NTDs and the preventive role of FA remain unclear. Here, we use human induced pluripotent stem cells (iPSCs) derived from fetuses with spina bifida aperta (SBA) to study the pathophysiology of NTDs and explore the effects of FA exposure. We report that FA exposure in SBA model is necessary for the proper formation and maturation of neural tube structures and robust differentiation of mesodermal derivatives. Additionally, we show that the folate antagonist methotrexate dramatically affects the formation of neural tube structures and FA partially reverts this aberrant phenotype. In conclusion, we present a novel model for human NTDs and provide evidence that it is a powerful tool to investigate the molecular mechanisms underlying NTDs, test drugs for therapeutic approaches
Loss-of-Function Mutations in SERPINB8 Linked to Exfoliative Ichthyosis with Impaired Mechanical Stability of Intercellular Adhesions
M.P. is supported by a Fellowship from the Deutsche Forschungsgemeinschaft. This work was supported in part by a generous donation of Israel and Ruthi Ram (E.S.) and from a British Heart Foundation Programme grant (D.P.K.)
The Extended Cleavage Specificity of Human Thrombin
Thrombin is one of the most extensively studied of all proteases. Its central role in the coagulation cascade as well as several other areas has been thoroughly documented. Despite this, its consensus cleavage site has never been determined in detail. Here we have determined its extended substrate recognition profile using phage-display technology. The consensus recognition sequence was identified as, P2-Pro, P1-Arg, P1β²-Ser/Ala/Gly/Thr, P2β²-not acidic and P3β²-Arg. Our analysis also identifies an important role for a P3β²-arginine in thrombin substrates lacking a P2-proline. In order to study kinetics of this cooperative or additive effect we developed a system for insertion of various pre-selected cleavable sequences in a linker region between two thioredoxin molecules. Using this system we show that mutations of P2-Pro and P3β²-Arg lead to an approximate 20-fold and 14-fold reduction, respectively in the rate of cleavage. Mutating both Pro and Arg results in a drop in cleavage of 200β400 times, which highlights the importance of these two positions for maximal substrate cleavage. Interestingly, no natural substrates display the obtained consensus sequence but represent sequences that show only 1β30% of the optimal cleavage rate for thrombin. This clearly indicates that maximal cleavage, excluding the help of exosite interactions, is not always desired, which may instead cause problems with dysregulated coagulation. It is likely exosite cooperativity has a central role in determining the specificity and rate of cleavage of many of these in vivo substrates. Major effects on cleavage efficiency were also observed for residues as far away as 4 amino acids from the cleavage site. Insertion of an aspartic acid in position P4 resulted in a drop in cleavage by a factor of almost 20 times
Essential Roles for Soluble Virion-Associated Heparan Sulfonated Proteoglycans and Growth Factors in Human Papillomavirus Infections
A subset of human papillomavirus (HPV) infections is causally related to the development of human epithelial tumors and cancers. Like a number of pathogens, HPV entry into target cells is initiated by first binding to heparan sulfonated proteoglycan (HSPG) cell surface attachment factors. The virus must then move to distinct secondary receptors, which are responsible for particle internalization. Despite intensive investigation, the mechanism of HPV movement to and the nature of the secondary receptors have been unclear. We report that HPV16 particles are not liberated from bound HSPG attachment factors by dissociation, but rather are released by a process previously unreported for pathogen-host cell interactions. Virus particles reside in infectious soluble high molecular weight complexes with HSPG, including syndecan-1 and bioactive compounds, like growth factors. Matrix mellatoproteinase inhibitors that block HSPG and virus release from cells interfere with virus infection. Employing a co-culture assay, we demonstrate HPV associated with soluble HSPG-growth factor complexes can infect cells lacking HSPG. Interaction of HPV-HSPG-growth factor complexes with growth factor receptors leads to rapid activation of signaling pathways important for infection, whereas a variety of growth factor receptor inhibitors impede virus-induced signaling and infection. Depletion of syndecan-1 or epidermal growth factor and removal of serum factors reduce infection, while replenishment of growth factors restores infection. Our findings support an infection model whereby HPV usurps normal host mechanisms for presenting growth factors to cells via soluble HSPG complexes as a novel method for interacting with entry receptors independent of direct virus-cell receptor interactions
Skin Barrier Homeostasis in Atopic Dermatitis: Feedback Regulation of Kallikrein Activity
Atopic dermatitis (AD) is a widely spread cutaneous chronic disease characterised by sensitive reactions (eg. eczema) to normally innocuous elements. Although relatively little is understood about its underlying mechanisms due to its complexity, skin barrier dysfunction has been recognised as a key factor in the development of AD. Skin barrier homeostasis requires tight control of the activity of proteases, called kallikreins (KLKs), whose activity is regulated by a complex network of protein interactions that remains poorly understood despite its pathological importance. Characteristic symptoms of AD include the outbreak of inflammation triggered by external (eg. mechanical and chemical) stimulus and the persistence and aggravation of inflammation even if the initial stimulus disappears. These characteristic symptoms, together with some experimental data, suggest the presence of positive feedback regulation for KLK activity by inflammatory signals. We developed simple mathematical models for the KLK activation system to study the effects of feedback loops and carried out bifurcation analysis to investigate the model behaviours corresponding to inflammation caused by external stimulus. The model analysis confirmed that the hypothesised core model mechanisms capture the essence of inflammation outbreak by a defective skin barrier. Our models predicted the outbreaks of inflammation at weaker stimulus and its longer persistence in AD patients compared to healthy control. We also proposed a novel quantitative indicator for inflammation level by applying principal component analysis to microarray data. The model analysis reproduced qualitative AD characteristics revealed by this indicator. Our results strongly implicate the presence and importance of feedback mechanisms in KLK activity regulation. We further proposed future experiments that may provide informative data to enhance the system-level understanding on the regulatory mechanisms of skin barrier in AD and healthy individuals
Personal attributes as determinants of timely care in rheumatoid arthritis
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Laparoscopic combined resection of liver metastases and colorectal cancer: a multicenter, case-matched study using propensity scores
Background: Combined laparoscopic resection of liver metastases and colorectal cancer (LLCR) may hold benefits for selected patients but could increase complication rates. Previous studies have compared LLCR with liver resection alone. Propensity score-matched studies comparing LLCR with laparoscopic colorectal cancer resection (LCR) alone have not been performed. Methods: A multicenter, case-matched study was performed comparing LLCR (2009β2016, 4 centers) with LCR alone (2009β2016, 2 centers). Patients were matched based on propensity scores in a 1:1 ratio. Propensity scores were calculated with the following preoperative variables: age, sex, ASA grade, neoadjuvant radiotherapy, type of colorectal resection and T and N stage of the primary tumor. Outcomes were compared using paired tests. Results: Out of 1020 LCR and 64 LLCR procedures, 122 (2 Γ 61) patients could be matched. All 61 laparoscopic liver resections were minor hepatectomies, mostly because of a solitary liver metastasis (n = 44, 69%) of small size (β€ 3Β cm) (n = 50, 78%). LLCR was associated with a modest increase in operative time [206 (166β308) vs. 197 (148β231) min, p = 0.057] and blood loss [200 (100β700) vs. 75 (5β200) ml, p = 0.011]. The rate of ClavienβDindo grade 3 or higher complications [9 (15%) vs. 13 (21%), p = 0.418], anastomotic leakage [5 (8%) vs. 4 (7%), p = 1.0], conversion rate [3 (5%) vs. 5 (8%), p = 0.687] and 30-day mortality [0 vs. 1 (2%), p = 1.0] did not differ between LLCR and LCR. Conclusion: In selected patients requiring minor hepatectomy, LLCR can be safely performed without increasing the risk of postoperative morbidity compared to LCR alone