Project description:The proton-activated chloride (PAC) channel (also known as acid-sensitive outwardly rectifying anion channel, ASOR) plays a critical role in acid-induced cell death and endocytosis. However, little is known about the regulatory factors and binding partners of PAC. In this study, we discovered that transfer RNA (tRNA) interacts directly with PAC as an unexpected binding partner. Using cryo-electron microscopy, we determined that two PAC trimers and one co-purified tRNA molecule form a stable complex via a highly conserved KR motif, representing the closed conformation. tRNA is located on the intracellular side of PAC, blocking the channel pores. Furthermore, electrophysiological data showed that tRNA modulates chloride currents and channel open probability of PAC, thus protecting against acid-induced cell death. Our study provides insight into the regulation of PAC activity by cytosolic tRNA and extends the role of tRNAs in pathological and physiological events.
Project description:STING transmits signals downstream of the cytosolic DNA sensor cGAS, leading to transcriptional up-regulation of cytokines. However, components of the STING signaling pathway, such as IRF3 and IFNAR1, are not essential for autoinflammatory disease in STING gain-of-function (SAVI) mice. Recent discoveries revealed that STING also functions as a proton channel that deacidifies the Golgi. Since pH impacts Golgi enzyme activity, protein maturation, and trafficking, we hypothesized that STING proton channel activity influences multiple Golgi functions. Here, we show that STING-mediated proton efflux non-transcriptionally regulates Golgi trafficking of protein cargos. This process requires the Golgi-associated protein ArfGAP2, a cell type-specific dual regulator of STING-mediated proton efflux and signaling. Deletion of ArfGAP2 in hematopoietic and endothelial cells markedly reduces STING-mediated cytokine and chemokine secretion, immune cell activation, and autoinflammatory pathology in SAVI mice. Thus, ArfGAP2 facilitates STING-mediated signaling and cytokine release in hematopoietic cells, significantly contributing to autoinflammatory disease pathogenesis.
Project description:STING transmits signals downstream of the cytosolic DNA sensor cGAS, leading to transcriptional up-regulation of cytokines. However, components of the STING signaling pathway, such as IRF3 and IFNAR1, are not essential for autoinflammatory disease in STING gain-of-function (SAVI) mice. Recent discoveries revealed that STING also functions as a proton channel that deacidifies the Golgi. Since pH impacts Golgi enzyme activity, protein maturation, and trafficking, we hypothesized that STING proton channel activity influences multiple Golgi functions. Here, we show that STING-mediated proton efflux non-transcriptionally regulates Golgi trafficking of protein cargos. This process requires the Golgi-associated protein ArfGAP2, a cell type-specific dual regulator of STING-mediated proton efflux and signaling. Deletion of ArfGAP2 in hematopoietic and endothelial cells markedly reduces STING-mediated cytokine and chemokine secretion, immune cell activation, and autoinflammatory pathology in SAVI mice. Thus, ArfGAP2 facilitates STING-mediated signaling and cytokine release in hematopoietic cells, significantly contributing to autoinflammatory disease pathogenesis.
Project description:Taste substances are received by taste receptors expressed in taste cells. “Salty taste” sensation is evoked when sodium and chloride ions are present together in the oral cavity. The presence of an epithelial cation channel that receives Na+ has previously been reported. However, no molecular entity involving Cl- receptors has been elucidated. We report the strong expression of transmembrane channel-like 4 (TMC4) in the circumvallate and foliate papillae projected to the glossopharyngeal nerve, mediating a high-concentration of NaCl. Electrophysiological analysis using HEK293T cells revealed that TMC4 was a voltage-dependent Cl- channel and the consequent currents were completely inhibited by NPPB, an anion channel blocker. This channel could be activated without an increase in intracellular calcium ion. TMC4 allowed permeation of organic anions including gluconate, but their current amplitudes at positive potentials were less than that of Cl-. Tmc4-deficient mice showed significantly weaker glossopharyngeal nerve response to high-concentration of NaCl than the wild-type littermates. These results indicated that TMC4 is a novel chloride channel that responds to high-concentration of NaCl.
Project description:STING transmits signals downstream of the cytosolic DNA sensor cGAS, leading to transcriptional up-regulation of cytokines. However, components of the STING signaling pathway, such as IRF3 and IFNAR1, are not essential for autoinflammatory disease in STING gain-of-function (SAVI) mice. Recent findings indicate that STING can also function as a proton channel that deacidifies the Golgi. Since pH impacts Golgi enzyme activity, protein maturation, and trafficking, we hypothesized that STING proton channel activity influences multiple Golgi functions. Here, we show that STING-mediated proton efflux non-transcriptionally regulates Golgi trafficking of protein cargos. This process requires the Golgi-associated protein ArfGAP2, a cell type-specific dual regulator of STING-mediated proton efflux and signaling. Deletion of ArfGAP2 in hematopoietic and endothelial cells markedly reduces STING-mediated cytokine and chemokine secretion, immune cell activation, and autoinflammatory pathology in SAVI mice. Thus, ArfGAP2 facilitates STING-mediated signaling and cytokine release in hematopoietic cells, significantly contributing to autoinflammatory disease pathogenesis.
Project description:Methylene diphenyl diisocyanate is a chemical known to cause asthma. The present study uses mice to investigate exposure-induced changes in lung gene expression and effects of a chloride channel inhibitor We used microarrays to detail global whole lung gene expression following respiratory tract exposure to methylene diphenyl diisocyanate (MDI) vs. control exposure in mice immune-sensitized to MDI by prior skin exposure. In some studies mice were given a chloride channel inhibitor (crofelemer) via the respiratory tract before MDI.
Project description:Multi-epitope affinity purification mass spectrometry (meAP-MS) analysis of TMEM9-, TMEM9B- and CLC3- associated proteins from solubilized mouse brain membranes identified chloride channel subtypes CLCN3, 4 and 5 as exclusive interaction partners of TMEM9 and TMM9B.
Project description:Primary aldosteronism (PA), a common cause of severe hypertension, features constitutive production of the adrenal steroid aldosterone. We analyzed a multiplex family with familial hyperaldosteronism type II (FH-II) and 80 additional probands with unsolved early-onset PA. Eight probands had novel heterozygous variants in CLCN2, including two de novo mutations and four independent occurrences of the identical p.Arg172Gln mutation; all relatives with early-onset PA carried the CLCN2 variant found in probands. CLCN2 encodes a voltage-gated chloride channel expressed in adrenal glomerulosa that opens at hyperpolarized membrane potentials. In this data set, we examined RNA expression in H295R cells transfected with empty vector, WT and p.Arg172Gln CLCN2. Expression of CLCN2 led to increased expression of CYP11B2 and its upstream regulator NR4A2.
Project description:Lysosomes are essential organelles for cellular homeostasis. Defective lysosomes are associated with many human diseases, such as lysosomal storage disorders (LSD). How the cell detects lysosomal defects and then restores lysosomal function remain incompletely understood. Here, we show that STING mediates a common neuroinflammatory gene signature in three distinct lysosomal storage disorders, Galctwi/twi, Ppt1-/-, and Cln7-/-. Transcriptomic analysis of Galctwi/twi brain tissue revealed that STING also mediates the expression of a broad panel of lysosomal genes that are part of the CLEAR (Coordinated Lysosomal Expression and Regulation) signaling pathway, which is regulated by transcriptional factor EB (TFEB). Immunohistochemical and single-nucleus RNA-seq analysis show that STING regulates lysosomal gene expression in microglia in LSD mice. Mechanistically, we show that STING activation in both human and mouse cells leads to TFEB dephosphorylation, nuclear translocation, and expression of target lysosomal genes. In addition, STING-mediated TFEB activation requires its proton channel function, the V-ATPase-ATG5-ATG8 cascade, and is independent of immune signaling. Functionally, we show that the STING-proton channel-TFEB axis plays a role in facilitating lysosomal repair. Together, our data identify STING-TFEB as a lysosomal quality control and recovery mechanism that responds to both genetic and chemically induced lysosomal dysfunction.