Increased IgE-dependent mast cell activation and anaphylactic responses in mice lacking the calcium-activated nonselective cation channel TRPM4

Abstract

Mast cells are key effector cells in allergic reactions. Aggregation of the receptor FceRI in mast cells triggers the influx of calcium (Ca 2+ ) and the release of inflammatory mediators. Here we show that transient receptor potential TRPM4 proteins acted as calcium-activated nonselective cation channels and critically determined the driving force for Ca 2+ influx in mast cells. Trpm4 -/-bone marrow-derived mast cells had more Ca 2+ entry than did TRPM4 +/+ cells after FceRI stimulation. Consequently, Trpm4 -/-bone marrow-derived mast cells had augmented degranulation and released more histamine, leukotrienes and tumor necrosis factor. Trpm4 -/-mice had a more severe IgE-mediated acute passive cutaneous anaphylactic response, whereas late-phase passive cutaneous anaphylaxis was not affected. Our results establish the physiological function of TRPM4 channels as critical regulators of Ca 2+ entry in mast cells.Mast cells are bone marrow-derived hematopoietic cells localized near surfaces exposed to the environment, such as the skin, the airway epithelia and the intestine, where pathogens, allergens and other environmental agents are frequently encountered 1 . Activation and degranulation of mast cells is a key step in the pathogenesis of allergic diseases such as bronchial asthma and systemic anaphylaxis 2 . An allergic reaction develops when allergens encountered by antigen-presenting cells are processed and presented to T cells. Ensuing T helper type 2 responses cause B cells to produce allergen-specific immunoglobulin E (IgE). The IgE molecules bind to the receptor FceRI on the surfaces of mast cells. After re-exposure to the allergen, FceRI-associated IgE molecules bind allergen and aggregate, thereby activating mast cells. Activated mast cells secrete preformed mediators, including proteases and vasoactive amines, such as histamine, that are stored in cytoplasmic granules. In addition, mast cell activation results in the de novo synthesis of proinflammatory lipid mediators, cytokines and chemokines. The instant release of histamine is crucial for the development of immediate-type allergic reactions that result in vasodilatation, increased vascular permeability and smooth muscle contraction 1,2 . In addition, IgE-dependent mast cell activation may be complemented by signaling cascades triggered by several endogenous ligands, such as adenosine, resulting in the amplification and maintenance of FceRI-mediated degranulation 3,4 .FceRI crosslinking activates many signaling molecules 5,6 . A chief 'downstream' target is phospholipase C-g1, which catalyzes the hydrolysis of phosphatidylinositol-4,5-bisphosphate to diacylglycerol and inositol-1,4,5-trisphosphate 5 . In contrast, adenosine stimulation involves the activation of G ai protein-coupled A 3 adenosine receptors in mouse mast cells, which leads to the activation of phospholipase C and phospholipase D through G bg protein and phosphatidylinositol-3-OH kinase-g 7,8 . Inositol-1,4,5-trisphosphate and diacylglycerol promote the activation of protein kinase C an...

TRP channels in neurogastroenterology: opportunities for therapeutic intervention

“…In mice lacking TRPM4, bone marrow-derived mast cells had augmented degranulation and released more histamine, leukotrienes and tumour necrosis factor due to increased Ca 2+ entry after FcepsilonRI stimulation (Vennekens et al, 2007). TRPM4 is also involved in the migration of bone marrow-derived mast cells by regulation of Ca 2+ -dependent actin cytoskeleton rearrangements (Vennekens et al, 2007;Shimizu et al, 2009). TRPM4 could be considered a therapeutic target in GI disorders that involve mast cell activation/degranulation, such as food allergies, mastocytosis and IBS (Bischoff, 2009).…”

Bernd Nilius: The Bard of ion channels. Congratulations on 65th birthday

“…Bernd also demonstrated the role of TRPM5 in temperature-sensitivity of taste [8], and soon thereafter, he discovered the molecular mechanism of temperature sensing by TRP channels [12]. Bernd published the first phenotype of TRPM4, indicating a mast cell gain of function resulting in anaphylaxia and an increased type 1 allergic response [9]. He further discovered a wide range of pathological potential of TRPM4 in variety of diseases [6].…”

Mutagenesis and Temperature-Sensitive Little Machines

“…A second study used the same strategy to target a region of the gene spanning from exons 3 to 6 [67]. Studies using the TRPM4 deficient mice show that this channel, like TRPM2, plays a role in controlling intracellular calcium levels during mast cell activation and dendritic cell migration [66][67][68]. It has also been shown that this ion channel helps to limit catecholamine release from chromaffin cells, indicating that TRPM4 -/-mice have an increased sympathetic tone and hypertension [69].…”

“…Knockout mice for TRPM4 were first generated by a Cre-loxP strategy that excised exons 15 and 16 of the gene (containing the first membrane-spanning segment of the protein), replacing them by a PGK-neo r cassette that was removed by Cre recombinase [66]. A second study used the same strategy to target a region of the gene spanning from exons 3 to 6 [67].…”