The SLC26 transporters are a family of mostly luminal Cl− and HCO3 − transporters. The transport mechanism and the Cl−/HCO3 − stoichiometry are not known for any member of the family. To address these questions, we simultaneously measured the HCO3 − and Cl− fluxes and the current or membrane potential of slc26a3 and slc26a6 expressed in Xenopus laevis oocytes and the current of the transporters expressed in human embryonic kidney 293 cells. slc26a3 mediates a coupled 2Cl−/1HCO3 − exchanger. The membrane potential modulated the apparent affinity for extracellular Cl− of Cl−/HCO3 − exchange by slc26a3. Interestingly, the replacement of Cl− with NO3 − or SCN− uncoupled the transport, with large NO3 − and SCN− currents and low HCO3 − transport. An apparent uncoupled current was also developed during the incubation of slc26a3-expressing oocytes in HCO3 −-buffered Cl−-free media. These findings were used to develop a turnover cycle for Cl− and HCO3 − transport by slc26a3. Cl− and HCO3 − flux measurements revealed that slc26a6 mediates a 1Cl−/2HCO3 − exchange. Accordingly, holding the membrane potential at 40 and −100 mV accelerated and inhibited, respectively, Cl−-mediated HCO3 − influx, and holding the membrane potential at −100 mV increased HCO3 −-mediated Cl− influx. These findings indicate that slc26a6 functions as a coupled 1Cl−/2HCO3 − exchanger. The significance of isoform-specific Cl− and HCO3 − transport stoichiometry by slc26a3 and slc26a6 is discussed in the context of diseases of epithelial Cl− absorption and HCO3 − secretion.

SLC26A9 is a member of the SLC26 family of anion transporters, which is expressed at high levels in airway and gastric surface epithelial cells.

Unexpectedly, deletion of slc26a6 in mice and measurement of fluid and HCO 3 À secretion into sealed intralobular pancreatic ducts revealed that deletion of slc26a6 enhanced spontaneous and decreased stimulated secretion. Remarkably, inhibition of CFTR activity with CFTR inh -172, knock-down of CFTR by siRNA and measurement of CFTR current in WT and slc26a6 À/À duct cells revealed that deletion of slc26a6 resulted in dis-regulation of CFTR activity by removal of tonic inhibition of CFTR by slc26a6. These findings reveal the intricate regulation of CFTR activity by slc26a6 in both the resting and stimulated states and the essential role of slc26a6 in pancreatic HCO 3 À secretion in vivo.

− /HCO 3 − exchange by Slc26a6, but had no effect on I − secretion by Slc26a4. Accordingly, deletion of Slc26a6, but not deletion of Slc26a4, results in dysregulation of CFTR. These findings provide the first evidence for a selective role of the SLC26 transporters expressed in the same tissue in epithelial anion transport and suggest that transport specificity is achieved by both the properties of the transporters and the composition of the complexes they form.

NS, Terada LS, Nwariaku FE. Regulation of VEGF-induced endothelial cell migration by mitochondrial reactive oxygen species.

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Evodiamine is an alkaloidal compound with antiobesity effects that have been thought to be due to uncoupling protein-1 (UCP1) thermogenesis similar to the effects of capsaicin, but the underlying mechanisms are poorly understood. To clarify the mechanisms, we first examined whether the antiobesity effect of evodiamine could be attributed to the involvement of UCP1. When UCP1-knockout mice were fed a high-fat diet with 0.03% evodiamine (wt/wt) for 2 months, the increases in body weight, adiposity, and the serum levels of leptin and insulin were reduced in a manner indistinguishable from control mice fed a high-fat diet with evodiamine, suggesting that evodiamine triggered a UCP1-independent mechanism to prevent diet-induced obesity. By using preadipocyte cultures, we found that evodiamine, but not capsaicin, increased phosphorylation of ERK/MAPK, reduced the expression of transcription factors such as peroxisome proliferator-activated receptor-gamma, and strongly inhibited adipocyte differentiation. Evodiamine treatment also reduced insulin-stimulated phosphorylation of Akt, a crucial regulator of adipocyte differentiation; and the reduction of phosphorylated-Akt and augmentation of phosphorylated ERK were reversed by blockade of the MAPK kinase/MAPK signaling pathway, restoring adipogenesis in the cultures. The changes in ERK and Akt phosphorylation levels were also observed in white adipose tissues of UCP1-knockout mice fed the evodiamine diet. These findings suggest that evodiamine has a potential to prevent the development of diet-induced obesity in part by inhibiting adipocyte differentiation through ERK activation and its negative cross talk with the insulin signaling pathway.

TMEM16F is a Ca2+ -gated ion channel that is required for Ca2+ -activated phosphatidylserine exposure on the surface of many eukaryotic cells. TMEM16F is widely expressed and has roles in platelet activation during blood clotting, bone formation and T cell activation. By combining microscopy and patch clamp recording we demonstrate that activation of TMEM16F by Ca2+ ionophores in Jurkat T cells triggers large-scale surface membrane expansion in parallel with phospholipid scrambling. With continued ionophore application,TMEM16F-expressing cells then undergo extensive shedding of ectosomes. The T cell co-receptor PD-1 is selectively incorporated into ectosomes. This selectivity depends on its transmembrane sequence. Surprisingly, cells lacking TMEM16F not only fail to expand surface membrane in response to elevated cytoplasmic Ca2+, but instead undergo rapid massive endocytosis with PD-1 internalisation. These results establish a new role for TMEM16F as a regulator of Ca2+ activated membrane trafficking.