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Yang Z.,Laboratory of Allergic Diseases | Balenga N.,Laboratory of Allergic Diseases | Cooper P.R.,University of Pennsylvania | Damera G.,University of Pennsylvania | And 4 more authors.
American Journal of Respiratory Cell and Molecular Biology | Year: 2012

Severe asthma is associated with fixed airway obstruction attributable to inflammation, copious luminal mucus, and increased airway smooth muscle (ASM) mass. Paradoxically, studies demonstrated that the hypertrophic and hyperplastic ASM characteristic of severe asthma has reduced contractile capacity. We compared the Gprotein-coupled receptor (GPCR)-induced Ca2+ mobilization and expression of GPCRs and signaling proteins related to procontractile signaling in ASM derived postmortem from subjects who died of nonrespiratory causes, with cells from subjects who died of asthma. Despite the increased or comparable expression of contraction-promoting GPCRs (bradykinin B2 or histamine H1 and protease-activated receptor 1, respectively) in asthmatic ASM cells relative to cells from healthy donors, asthmatic ASM cells exhibited reduced histamine-induced Ca2+ mobilization and comparable responses to bradykinin and thrombin, suggesting a postreceptor signaling defect. Accordingly, the expression of regulator of G-protein signaling-5 (RGS5), an inhibitor of ASM contraction, was increased in cultured, asthmatic ASM cells and in bronchial smooth muscle bundles of both human subjects with asthma and allergen-challenged mice, relative to those of healthy human subjects or naive mice. The over-expression of RGS5 impaired the release of Ca2+ to thrombin, histamine, and carbachol, and reduced the contraction of precision-cut lung slices to carbachol. These results suggest that increased RGS5 expression contributes to decreased myocyte shortening in severe and fatal asthma. Copyright © 2012 by the American Thoracic Society. Source


Kotlarz D.,Hannover Medical School | Kotlarz D.,Ludwig Maximilians University of Munich | Zietara N.,Hannover Medical School | Zietara N.,Ludwig Maximilians University of Munich | And 35 more authors.
Journal of Experimental Medicine | Year: 2013

Primary immunodeficiencies (PIDs) represent exquisite models for studying mechanisms of human host defense. In this study, we report on two unrelated kindreds, with two patients each, who had cryptosporidial infections associated with chronic cholangitis and liver disease. Using exome and candidate gene sequencing, we identified two distinct homozygous loss-of-function mutations in the interleukin-21 receptor gene (IL21R; c.G602T, p.Arg201Leu and c.240_245delCTGCCA, p.C81_H82del). The IL-21RArg201Leu mutation causes aberrant trafficking of the IL-21R to the plasma membrane, abrogates IL-21 ligand binding, and leads to defective phosphorylation of signal transducer and activator of transcription 1 (STAT1), STAT3, and STAT5. We observed impaired IL-21-induced proliferation and immunoglobulin class-switching in B cells, cytokine production in T cells, and NK cell cytotoxicity. Our study indicates that human IL-21R deficiency causes an immunodeficiency and highlights the need for early diagnosis and allogeneic hematopoietic stem cell transplantation in affected children. © 2013 Kotlarz et al. Source


Chan E.C.,Laboratory of Allergic Diseases | Bai Y.,Laboratory of Allergic Diseases | Bandara G.,Laboratory of Allergic Diseases | Simakova O.,U.S. National Institutes of Health | And 8 more authors.
Experimental Hematology | Year: 2013

Stem cell factor-dependent KIT activation is an essential process for mast cell homeostasis. The two major splice variants of KIT differ by the presence or absence of four amino acids (GNNK) at the juxta-membrane region of the extracellular domain. We hypothesized that the expression pattern of these variants differs in systemic mastocytosis and that transcripts containing the KIT D816V mutation segregate preferentially to one GNNK variant. A quantitative real-time PCR assay to assess GNNK- and GNNK+ transcripts from bone marrow mononuclear cells was developed. The GNNK-/GNNK+ copy number ratio showed a trend toward a positive correlation with the percentage of neoplastic mast cell involvement, and KIT D816V containing transcripts displayed a significantly elevated GNNK-/GNNK+ copy number ratio. Relative expression of only the GNNK- variant correlated with increasing percentage of neoplastic mast cell involvement. A mast cell transfection system revealed that the GNNK- isoform of wild type KIT was associated with increased granule formation, histamine content, and growth. When accompanying the KIT D816V mutation, the GNNK-isoform enhanced cytokine-free metabolism and moderately reduced sensitivity to the tyrosine kinase inhibitor, PKC412. These data suggest that neoplastic mast cells favor a GNNK- variant predominance, which in turn enhances the activating potential of the KIT D816V mutation and thus could influence therapeutic sensitivity in systemic mastocytosis. © 2013. Source

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