Publications

• Protons Regulate Vesicular Glutamate Transporters through an Allosteric Mechanism.

  Eriksen J., Chang R., McGregor M., Silm K., Suzuki T., Edwards R.H.

  The quantal nature of synaptic transmission requires a mechanism to transport neurotransmitter into synaptic vesicles without promoting non-vesicular efflux across the plasma membrane. Indeed, the vesicular transport of most classical transmitters involves a mechanism of H(+) exchange, which restr ... >> More

  The quantal nature of synaptic transmission requires a mechanism to transport neurotransmitter into synaptic vesicles without promoting non-vesicular efflux across the plasma membrane. Indeed, the vesicular transport of most classical transmitters involves a mechanism of H(+) exchange, which restricts flux to acidic membranes such as synaptic vesicles. However, vesicular transport of the principal excitatory transmitter glutamate depends primarily on membrane potential, which would drive non-vesicular efflux, and the role of protons is unclear. Adapting electrophysiology to record currents associated with the vesicular glutamate transporters (VGLUTs), we characterize a chloride conductance that is gated by lumenal protons and chloride and supports glutamate uptake. Rather than coupling stoichiometrically to glutamate flux, lumenal protons and chloride allosterically activate vesicular glutamate transport. Gating by protons serves to inhibit what would otherwise be substantial non-vesicular glutamate efflux at the plasma membrane, thereby restricting VGLUT activity to synaptic vesicles. << Less

  Neuron 90:768-780(2016) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• ASCT-1 is a neutral amino acid exchanger with chloride channel activity.

  Zerangue N., Kavanaugh M.P.

  The ubiquitous transport activity known as system ASC is characterized by a preference for small neutral amino acids including alanine, serine, and cysteine. ASCT-1 and ASCT-2, recently cloned transporters exhibiting system ASC-like selectivity, are members of a major amino acid transporter family ... >> More

  The ubiquitous transport activity known as system ASC is characterized by a preference for small neutral amino acids including alanine, serine, and cysteine. ASCT-1 and ASCT-2, recently cloned transporters exhibiting system ASC-like selectivity, are members of a major amino acid transporter family that includes a number of glutamate transporters. Here we show that ASCT1 functions as an electroneutral exchanger that mediates negligible net amino acid flux. The electrical currents previously shown to be associated with ASCT1-mediated transport result from activation of a thermodynamically uncoupled chloride conductance with permeation properties similar to those described for the glutamate transporter subfamily. Like glutamate transporters, ASCT1 activity requires extracellular Na+. However, unlike glutamate transporters, which mediate net flux and complete a transport cycle by countertransport of K+, ASCT-1 mediates only homo- and heteroexchange of amino acids and is insensitive to K+. The properties of ASCT-1 suggest that it may function to equilibrate different pools of neutral amino acids and provide a mechanism to link amino acid concentration gradients. << Less

  J Biol Chem 271:27991-27994(1996) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• SLC26A7 is a Cl- channel regulated by intracellular pH.

  Kim K.H., Shcheynikov N., Wang Y., Muallem S.

  Members of the SLC26 transporter family play an essential role in several epithelial functions, as revealed by diseases associated with mutations in members of the family. Several members were shown to function as Cl(-) and HCO(3)(-) transporters that likely play an important role in epithelial Cl ... >> More

  Members of the SLC26 transporter family play an essential role in several epithelial functions, as revealed by diseases associated with mutations in members of the family. Several members were shown to function as Cl(-) and HCO(3)(-) transporters that likely play an important role in epithelial Cl(-) absorption and HCO(3)(-) secretion. However, the mechanism of most transporters is not well understood. SLC26A7 is a member of the SLC26 transporter family reported to be expressed in the basolateral membrane of the cortical collecting duct and parietal cells and functions as a coupled Cl(-)/HCO(3)(-) exchanger. In the present work we examined the transport properties of SLC26A7 to determine its transport characteristics and electrogenicity. We found that when expressed in Xenopus oocytes or HEK293 cells SLC26A7 functions as a pH(i)-regulated Cl(-) channel with minimal OH(-)/HCO(3)(-) permeability. Expression of SLC26A7 in oocytes or HEK293 cells generated a Cl(-) current with linear I/V and an instantaneous current that was voltage- and time-independent. Based on measurement of reversal potential the selectivity of SLC26A7 is NO(3)(-)>>Cl(-)=Br(-)=I(-)>SO(4)(2-)=Glu(-), although I(-) partially inhibited the current. Incubating the cells with HCO(3)(-) or butyrate acidified the cytosol and increased the selectivity of SLC26A7 for Cl(-). Measurement of membrane potential and pH(i) showed minimal OH(-) and HCO(3)(-) transport by SLC26A7 when the cells were incubated in Cl(-)-containing or Cl(-)-free media. The activity of SLC26A7 was inhibited by all inhibitors of anion transporters tested, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, diphenylamine-2-carboxylic acid, and glybenclamide. These findings reveal that SLC26A7 functions as a unique Cl(-) channel that is regulated by intracellular H(+). << Less

  J. Biol. Chem. 280:6463-6470(2005) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

• An intestinal zinc sensor regulates food intake and developmental growth.

  Redhai S., Pilgrim C., Gaspar P., Giesen L.V., Lopes T., Riabinina O., Grenier T., Milona A., Chanana B., Swadling J.B., Wang Y.F., Dahalan F., Yuan M., Wilsch-Brauninger M., Lin W.H., Dennison N., Capriotti P., Lawniczak M.K.N., Baines R.A., Warnecke T., Windbichler N., Leulier F., Bellono N.W., Miguel-Aliaga I.

  In cells, organs and whole organisms, nutrient sensing is key to maintaining homeostasis and adapting to a fluctuating environment¹. In many animals, nutrient sensors are found within the enteroendocrine cells of the digestive system; however, less is known about nutrient sensing in the ... >> More

  In cells, organs and whole organisms, nutrient sensing is key to maintaining homeostasis and adapting to a fluctuating environment¹. In many animals, nutrient sensors are found within the enteroendocrine cells of the digestive system; however, less is known about nutrient sensing in their cellular siblings, the absorptive enterocytes¹. Here we use a genetic screen in Drosophila melanogaster to identify Hodor, an ionotropic receptor in enterocytes that sustains larval development, particularly in nutrient-scarce conditions. Experiments in Xenopus oocytes and flies indicate that Hodor is a pH-sensitive, zinc-gated chloride channel that mediates a previously unrecognized dietary preference for zinc. Hodor controls systemic growth from a subset of enterocytes-interstitial cells-by promoting food intake and insulin/IGF signalling. Although Hodor sustains gut luminal acidity and restrains microbial loads, its effect on systemic growth results from the modulation of Tor signalling and lysosomal homeostasis within interstitial cells. Hodor-like genes are insect-specific, and may represent targets for the control of disease vectors. Indeed, CRISPR-Cas9 genome editing revealed that the single hodor orthologue in Anopheles gambiae is an essential gene. Our findings highlight the need to consider the instructive contributions of metals-and, more generally, micronutrients-to energy homeostasis. << Less

  Nature 580:263-268(2020) [PubMed] [EuropePMC]

• SWELL1, a plasma membrane protein, is an essential component of volume-regulated anion channel.

  Qiu Z., Dubin A.E., Mathur J., Tu B., Reddy K., Miraglia L.J., Reinhardt J., Orth A.P., Patapoutian A.

  Maintenance of a constant cell volume in response to extracellular or intracellular osmotic changes is critical for cellular homeostasis. Activation of a ubiquitous volume-regulated anion channel (VRAC) plays a key role in this process; however, its molecular identity in vertebrates remains unknow ... >> More

  Maintenance of a constant cell volume in response to extracellular or intracellular osmotic changes is critical for cellular homeostasis. Activation of a ubiquitous volume-regulated anion channel (VRAC) plays a key role in this process; however, its molecular identity in vertebrates remains unknown. Here, we used a cell-based fluorescence assay and performed a genome-wide RNAi screen to find components of VRAC. We identified SWELL1 (LRRC8A), a member of a four-transmembrane protein family with unknown function, as essential for hypotonicity-induced iodide influx. SWELL1 is localized to the plasma membrane, and its knockdown dramatically reduces endogenous VRAC currents and regulatory cell volume decrease in various cell types. Furthermore, point mutations in SWELL1 cause a significant change in VRAC anion selectivity, demonstrating that SWELL1 is an essential VRAC component. These findings enable further molecular characterization of the VRAC channel complex and genetic studies for understanding the function of VRAC in normal physiology and disease. << Less

  Cell 157:447-458(2014) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Functional characterization of three novel tissue-specific anion exchangers SLC26A7, -A8, and -A9.

  Lohi H., Kujala M., Maekelae S., Lehtonen E., Kestilae M., Saarialho-Kere U., Markovich D., Kere J.

  A second distinct family of anion exchangers, SLC26, in addition to the classical SLC4 (or anion exchanger) family, has recently been delineated. Particular interest in this gene family is stimulated by the fact that the SLC26A2, SLC26A3, and SLC26A4 genes have been recognized as the disease genes ... >> More

  A second distinct family of anion exchangers, SLC26, in addition to the classical SLC4 (or anion exchanger) family, has recently been delineated. Particular interest in this gene family is stimulated by the fact that the SLC26A2, SLC26A3, and SLC26A4 genes have been recognized as the disease genes mutated in diastrophic dysplasia, congenital chloride diarrhea, and Pendred syndrome, respectively. We report the expansion of the SLC26 gene family by characterizing three novel tissue-specific members, named SLC26A7, SLC26A8, and SLC26A9, on chromosomes 8, 6, and 1, respectively. The SLC26A7-A9 proteins are structurally very similar at the amino acid level to the previous family members and show tissue-specific expression in kidney, testis, and lung, respectively. More detailed characterization by immunohistochemistry and/or in situ hybridization localized SLC26A7 to distal segments of nephrons, SLC26A8 to developing spermatocytes, and SLC26A9 to the lumenal side of the bronchiolar and alveolar epithelium of lung. Expression of SLC26A7-A9 proteins in Xenopus oocytes demonstrated chloride, sulfate, and oxalate transport activity, suggesting that they encode functional anion exchangers. The functional characterization of the novel tissue-specific members may provide new insights to anion transport physiology in different parts of body. << Less

  J. Biol. Chem. 277:14246-14254(2002) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• CLN7 is an organellar chloride channel regulating lysosomal function.

  Wang Y., Zeng W., Lin B., Yao Y., Li C., Hu W., Wu H., Huang J., Zhang M., Xue T., Ren D., Qu L., Cang C.

  Neuronal ceroid lipofuscinoses (NCLs) are a group of autosomal recessive lysosomal storage diseases. One variant form of late-infantile NCL (vLINCL) is caused by mutations of a lysosomal membrane protein CLN7, the function of which has remained unknown. Here, we identified CLN7 as a novel endolyso ... >> More

  Neuronal ceroid lipofuscinoses (NCLs) are a group of autosomal recessive lysosomal storage diseases. One variant form of late-infantile NCL (vLINCL) is caused by mutations of a lysosomal membrane protein CLN7, the function of which has remained unknown. Here, we identified CLN7 as a novel endolysosomal chloride channel. Overexpression of CLN7 increases endolysosomal chloride currents and enlarges endolysosomes through a Ca²⁺/calmodulin-dependent way. Human CLN7 and its yeast homolog exhibit characteristics of chloride channels and are sensitive to chloride channel blockers. Moreover, CLN7 regulates lysosomal chloride conductance, luminal pH, and lysosomal membrane potential and promotes the release of lysosomal Ca²⁺ through transient receptor potential mucolipin 1 (TRPML1). Knocking out CLN7 causes pathological features that are similar to those of patients with vLINCL, including retinal degeneration and autofluorescent lipofuscin. The pathogenic mutations in CLN7 lead to a decrease in chloride permeability, suggesting that reconstitution of lysosomal Cl⁻ homeostasis may be an effective strategy for the treatment of vLINCL. << Less

  Sci. Adv. 7:eabj9608-eabj9608(2021) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.