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ABSTRACT: Cross-linking of the IgE receptor (FcεRI) on mast cells plays a critical role in IgE-dependent allergy, including allergic rhinitis, asthma, anaphylaxis, and immediate-type hypersensitivity reactions. Previous studies have demonstrated that the K(+) channel, KCa3.1, plays a critical role in IgE-stimulated Ca(2+) entry and degranulation in both human and mouse mast cells. We now have shown that the class II phosphatidylinositol-3-kinase C2β (PI3KC2β) is necessary for FcεRI-stimulated activation of KCa3.1, Ca(2+) influx, cytokine production, and degranulation of bone marrow-derived mast cells (BMMC). In addition, we found that the E3 ubiquitin ligase, tripartite motif containing protein 27 (TRIM27), negatively regulates FcεRI activation of KCa3.1 and downstream signaling by ubiquitinating and inhibiting PI3KC2β. TRIM27(-/-) mice are also more susceptible in vivo to acute anaphylaxis. These findings identify TRIM27 as an important negative regulator of mast cells in vivo and suggest that PI3KC2β is a potential new pharmacologic target to treat IgE-mediated disease.
Molecular and cellular biology 05/2012; 32(15):3132-9. · 6.06 Impact Factor
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ABSTRACT: The K(+) channel KCa3.1 is required for Ca(2+) influx and the subsequent activation of CD4 T cells. The class II phosphatidylinositol 3 kinase C2β (PI3KC2β) is activated by the T-cell receptor (TCR) and is critical for KCa3.1 channel activation. Tripartite motif containing protein 27 (TRIM27) is a member of a large family of proteins that function as Really Interesting New Gene (RING) E3 ubiquitin ligases. We now show that TRIM27 functions as an E3 ligase and mediates lysine 48 polyubiquitination of PI3KC2β, leading to a decrease in PI3K enzyme activity. By inhibiting PI3KC2β, TRIM27 also functions to negatively regulate CD4 T cells by inhibiting KCa3.1 channel activity and TCR-stimulated Ca(2+) influx and cytokine production in Jurkat, primary human CD4 T cells, and Th0, Th1, and Th2 CD4 T cells generated from TRIM27(-/-) mice. These findings provide a unique mechanism for regulating class II PI3Ks, and identify TRIM27 as a previously undescribed negative regulator of CD4 T cells.
Proceedings of the National Academy of Sciences 11/2011; 108(50):20072-7. · 9.68 Impact Factor
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ABSTRACT: Nucleoside diphosphate kinases (NDPKs) are encoded by the Nme (non-metastatic cell) gene family. Although they comprise a family of 10 genes, NDPK-A and -B are ubiquitously expressed and account for most of the NDPK activity. We previously showed that NDPK-B activates the K(+) channel KCa3.1 via histidine phosphorylation of the C terminus of KCa3.1, which is required for T cell receptor-stimulated Ca(2+) flux and proliferation of activated naive human CD4 T cells. We now report the phenotype of NDPK-B(-/-) mice. NDPK-B(-/-) mice are phenotypically normal at birth with a normal life span. Although T and B cell development is normal in NDPK-B(-/-) mice, KCa3.1 channel activity and cytokine production are markedly defective in T helper 1 (Th1) and Th2 cells, whereas Th17 function is normal. These findings phenocopy studies in the same cells isolated from KCa3.1(-/-) mice and thereby support genetically that NDPK-B functions upstream of KCa3.1. NDPK-A and -B have been linked to an astonishing array of disparate cellular and biochemical functions, few of which have been confirmed in vivo in physiological relevant systems. NDPK-B(-/-) mice will be an essential tool with which to definitively address the biological functions of NDPK-B. Our finding that NDPK-B is required for activation of Th1 and Th2 CD4 T cells, together with the normal overall phenotype of NDPK-B(-/-) mice, suggests that specific pharmacological inhibitors of NDPK-B may provide new opportunities to treat Th1- and Th2-mediated autoimmune diseases.
Journal of Biological Chemistry 09/2010; 285(50):38765-71. · 4.77 Impact Factor
