Karen Affleck

Human ClCa1 modulates anionic conduction of calcium-dependent chloride currents

Proteins of the CLCA gene family including the human ClCa1 (hClCa1) have been suggested to constitute a new family of chloride channels mediating Ca2+‐dependent Cl− currents. The present study examines the relationship between the hClCa1 protein and Ca2+‐dependent Cl− currents using heterologous expression of hClCa1 in HEK293 and NCIH522 cell lines and whole cell recordings. By contrast to previous reports claiming the absence of Cl− currents in HEK293 cells, we find that HEK293 and NCIH522 cell lines express constitutive Ca2+‐dependent Cl− currents and show that hClCa1 increases the amplitude of Ca2+‐dependent Cl− currents in those cells. We further show that hClCa1 does not modify the permeability sequence but increases the Cl− conductance while decreasing the GSCN−/GCl− conductance ratio from ∼2–3 to ∼1. We use an Eyring rate theory (two barriers, one site channel) model and show that the effect of hClCa1 on the anionic channel can be simulated by its action on lowering the first and the second energy barriers. We conclude that hClCa1 does not form Ca2+‐dependent Cl− channels per se or enhance the trafficking/insertion of constitutive channels in the HEK293 and NCIH522 expression systems. Rather, hClCa1 elevates the single channel conductance of endogenous Ca2+‐dependent Cl− channels by lowering the energy barriers for ion translocation through the pore.

Targeting phosphoinositide 3-kinase δ for allergic asthma

Chronic inflammation in the lung has long been linked to the pathogenesis of asthma. Central to this airway inflammation is a T-cell response to allergens, with Th2 cytokines driving the differentiation, survival and function of the major inflammatory cells involved in the allergic cascade. PI3Kδ (phosphoinositide 3-kinase δ) is a lipid kinase, expressed predominantly in leucocytes, where it plays a critical role in immune receptor signalling. A selective PI3Kδ inhibitor is predicted to block T-cell activation in the lung, reducing the production of pro-inflammatory Th2 cytokines. PI3Kδ is also involved in B-cell and mast cell activation. Therefore the inhibition of PI3Kδ should dampen down the inflammatory cascade involved in the asthmatic response through a wide breadth of pharmacology. Current anti-inflammatory therapies, which are based on corticosteroids, are effective in controlling inflammation in mild asthmatics, but moderate/severe asthmatic patients remain poorly controlled, experiencing recurrent exacerbations. Corticosteroids have no effect on mast cell degranulation and do not act directly on B-cells, so, overall, a PI3Kδ inhibitor has the potential to deliver improvements in onset of action, efficacy and reduced exacerbations in moderate/severe asthmatics. Additionally, PI3Kδ inhibition is expected to block effects of Th17 cells, which are increasingly implicated in steroid-insensitive asthma.

Identification of orally bioavailable small-molecule inhibitors of hematopoietic prostaglandin D2 synthase using X-ray fragment based drug discovery

Using X-ray crystallographic screening, fragments 4 and 6 were identified as inhibitors of hematopoietic prostaglandin D2 synthase (H-PGDS). Both fragments induced a small protein movement in the X-ray crystal structure relative to the apo structure, where the highly polar nature of the ligand complemented the induced protein conformation. The manuscript describes the fragment optimisation of 4 and 6 followed by fragment growth to lead molecule 10. This showed favourable physicochemical properties and evidence of oral activity in blocking PGD2 generation in vivo.

Regulatory T-cell–intrinsic amphiregulin is dispensable for suppressive function

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Orai and TRPC channel characterization in FcεRI‐mediated calcium signaling and mediator secretion in human mast cells

Inappropriate activation of mast cells via the FcεRI receptor leads to the release of inflammatory mediators and symptoms of allergic disease. Calcium influx is a critical regulator of mast cell signaling and is required for exocytosis of preformed mediators and for synthesis of eicosanoids, cytokines and chemokines. Studies in rodent and human mast cells have identified Orai calcium channels as key contributors to FcεRI‐initiated mediator release. However, until now the role of TRPC calcium channels in FcεRI‐mediated human mast cell signaling has not been published. Here, we show evidence for the expression of Orai 1,2, and 3 and TRPC1 and 6 in primary human lung mast cells and the LAD2 human mast cell line but, we only find evidence of functional contribution of Orai and not TRPC channels to FcεRI‐mediated calcium entry. Calcium imaging experiments, utilizing an Orai selective antagonist (Synta66) showed the contribution of Orai to FcεRI‐mediated signaling in human mast cells. Although, the use of a TRPC3/6 selective antagonist and agonist (GSK‐3503A and GSK‐2934A, respectively) did not reveal evidence for TRPC6 contribution to FcεRI‐mediated calcium signaling in human mast cells. Similarly, inactivation of STIM1‐regulated TRPC1 in human mast cells (as tested by transfecting cells with STIM1‐KK684‐685EE ‐ TRPC1 gating mutant) failed to alter FcεRI‐mediated calcium signaling in LAD2 human mast cells. Mediator release assays confirm that FcεRI‐mediated calcium influx through Orai is necessary for histamine and TNFα release but is differentially involved in the generation of cytokines and eicosanoids.