The Experts below are selected from a list of 6744 Experts worldwide ranked by ideXlab platform

Tianxin Yang - One of the best experts on this subject based on the ideXlab platform.

  • abstract p109 collecting duct renin and aldosterone regulate Potassium Homeostasis
    Hypertension, 2018
    Co-Authors: Yanting Chen, Changjiang Zou, Nirupama Ramkumar, Shiying Xie, Fei Wang, Renfei Luo, Tianxin Yang
    Abstract:

    The kalliuric action of the renin-angiotensin-aldosterone system (RAAS) is well established as highlighted by hyperkaliemia side effect of RAAS inhibitors but such action is usually ascribed to sys...

  • abstract p112 site 1 protease regulates Potassium Homeostasis via intrarenal renin angiotensin aldosterone system
    Hypertension, 2018
    Co-Authors: Yanting Chen, Shiying Xie, Fei Wang, Renfei Luo, Tianxin Yang
    Abstract:

    We previously reported that (pro)renin receptor is activated by K+ loading and is responsible for local generation of aldosterone (Aldo), contributing to the kaliuretic response. Furthermore, site-...

  • pro renin receptor regulates Potassium Homeostasis through a local mechanism
    American Journal of Physiology-renal Physiology, 2017
    Co-Authors: Hong Wang, Hui Fang, Li Zhou, Peng Sun, Tianxin Yang
    Abstract:

    (Pro)renin receptor (PRR) is highly expressed in the distal nephron, but it has an unclear functional implication. The present study was conducted to explore a potential role of renal PRR during high K+ (HK) loading. In normal Sprague-Dawley rats, a 1-wk HK intake increased renal expression of full-length PRR and urinary excretion of soluble PRR (sPRR). Administration of PRO20, a decoy peptide antagonist of PRR, in K+-loaded animals elevated plasma K+ level and decreased urinary K+ excretion, accompanied with suppressed urinary aldosterone excretion and intrarenal aldosterone levels. HK downregulated Na+-Cl- cotransporter (NCC) expression but upregulated CYP11B2 (cytochrome P-450, family 11, subfamily B, polypeptide 2), renal outer medullary K+ channel (ROMK), calcium-activated Potassium channel subunit α1 (α-BK), α-Na+-K+-ATPase (α-NKA), and epithelial Na+ channel subunit β (β-ENaC), all of which were blunted by PRO20. After HK loading was completed, urinary, but not plasma renin, was upregulated, which was blunted by PRO20. The same experiments that were performed using adrenalectomized (ADX) rats yielded similar results. Interestingly, spironolactone treatment in HK-loaded ADX rats attenuated kaliuresis but promoted natriuresis, which was associated with the suppressed responses of β-ENaC, α-NKA, ROMK, and α-BK protein expression. Taken together, we discovered a novel role of renal PRR in regulation of K+ Homeostasis through a local mechanism involving intrarenal renin-angiotensin-aldosterone system and coordinated regulation of membrane Na+- and K+-transporting proteins.

  • abstract p210 pro renin receptor regulates Potassium Homeostasis via intrarenal aldosterone
    Hypertension, 2016
    Co-Authors: Hong Wang, Hui Fang, Li Zhou, Peng Sun, Tianxin Yang
    Abstract:

    It has been shown that transgenic overexpression of human (pro)renin receptor (PRR) results in elevated aldosterone (Aldo) level with unclear functional implications. The present study examined a potential role of renal PRR during high K + (HK) loading. In normal SD rats, a 1-week HK intake (5% KCl in diet) induced a 3.4-fold increase in renal protein expression of full-length PRR and 4.2-fold increase in urinary excretion of soluble PRR (sPRR). Administration of PRO20, a decoy peptide antagonist of PRR, at 700 μg/kg/d via i.p. injections, to K + -loaded animals elevated plasma K + level (5.72+0.08 vs. 4.84±0.18 mM, p + excretion (2.52+0.11 vs. 3.43+0.19 mmol/24h, p + -K + -ATPase (596%), and β-ENaC (155%), all of which were significantly blunted by PRO20 (by 50 - 70%). The same maneuvers were applied to adrenalectomized (ADX) rats. Although plasma Aldo was extremely low and also unresponsive to HK loading, urinary Aldo excretion was elevated by 274% with this treatment, which was abolished by PRO20. The HK-induced responses of the above K + and Na + transporting proteins in ADX rats all persisted and also remained sensitive to PRO20. Additionally, spironolactone treatment in ADX rats was still effective in inhibiting kaliuresis induced by HK loading, resulting in hyperkalemia (Plasma K+: 5.13±0.07 vs. 4.19±0.27 mM, p + and K + transporting proteins to facilitate K + secretion.

Jorg Stulke - One of the best experts on this subject based on the ideXlab platform.

  • essentiality of c di amp in bacillus subtilis bypassing mutations converge in Potassium and glutamate Homeostasis
    bioRxiv, 2020
    Co-Authors: Larissa Kruger, Jan Gundlach, Christina Herzberg, Rolf Daniel, Anja Poehlein, Hermann Rath, Tiago Pedreira, Uwe Volker, Ulrike Mader, Jorg Stulke
    Abstract:

    ABSTRACT In order to adjust to changing environmental conditions, bacteria use nucleotide second messengers to transduce external signals and translate them into a specific cellular response. Cyclic di-adenosine monophosphate (c-di-AMP) is the only known essential nucleotide second messenger. In addition to the well-established role of this second messenger in the control of Potassium Homeostasis, we observed that glutamate is as toxic as Potassium for a c-di-AMP-free strain of the Gram-positive model bacterium Bacillus subtilis. In this work, we isolated suppressor mutants that allow growth of a c-di-AMP-free strain under these toxic conditions. Characterization of glutamate resistant suppressors revealed that they contain pairs of mutations, in most cases affecting glutamate and Potassium Homeostasis. Among these mutations, several independent mutations affected a novel glutamate transporter, AimA (Amino acid importer A, formerly YbeC). This protein is the major transporter for glutamate and serine in B. subtilis. Unexpectedly, some of the isolated suppressor mutants could suppress glutamate toxicity by a combination of mutations that affect phospholipid biosynthesis and a specific gain-of-function mutation of a mechanosensitive channel of small conductance (YfkC) suggesting the acquisition of a device for glutamate export. Cultivation of the c-di-AMP-free strain on complex medium was an even greater challenge because the amounts of Potassium, glutamate, and other osmolytes are substantially higher than in minimal mediu. Suppressor mutants viable on complex medium could only be isolated under anaerobic conditions if one of the two c-di-AMP receptor proteins, DarA or DarB, was absent. Also on complex medium, Potassium and osmolyte toxicity are the major bottlenecks for the growth of B. subtilis in the absence of c-di-AMP. Our results indicate that the essentiality of c-di-AMP in B. subtilis is caused by the global impact of the second messenger nucleotide on different aspects of cellular physiology. AUTHOR SUMMARY Bacteria are exposed to constantly changing environmental conditions. In order to respond to these changes, they use nucleotide second messengers to transduce external signals and translate them into a specific cellular response. Among the repertoire of bacterial second messenger nucleotides, cyclic di-AMP (c-di-AMP) stands out as it is the only second messenger that is essential for the bacteria that produce it, including the Gram-positive model organism Bacillus subtilis. C-di-AMP plays a major role in the control of Potassium Homeostasis, and we found that glutamate is toxic to a B. subtilis strain lacking c-di-AMP to the same extent as Potassium. These toxic conditions were the starting point for an extensive suppressor analysis, which led to the identification of a novel glutamate transporter (AimA). If the B. subtilis strain lacking c-di-AMP was cultivated on complex medium, the isolation of suppressor mutants was only possible under anaerobic conditions and if either of the two c-di-AMP-binding signal transduction proteins was absent. This suggests that these proteins are a major burden for the cell on complex medium in their c-di-AMP free state. Our result underline the complexity of c-di-AMP signaling and propose new directions for research.

  • the kupa and kupb proteins of lactococcus lactis il1403 are novel c di amp receptor proteins responsible for Potassium uptake
    Journal of Bacteriology, 2019
    Co-Authors: Johannes Gibhardt, Asan Turdiev, Fabian M Commichau, Ingrid Quintana, Elke Hammer, Christian Magni, Jorg Stulke
    Abstract:

    ABSTRACT Cyclic di-AMP (c-di-AMP) is a second messenger involved in diverse metabolic processes, including osmolyte uptake, cell wall Homeostasis, and antibiotic and heat resistance. In Lactococcus lactis, a lactic acid bacterium which is used in the dairy industry and as a cell factory in biotechnological processes, the only reported interaction partners of c-di-AMP are the pyruvate carboxylase and BusR, the transcription regulator of the busAB operon for glycine betaine uptake. However, recent studies uncovered a major role of c-di-AMP in the control of Potassium Homeostasis, and Potassium is the signal that triggers c-di-AMP synthesis. In this study, we have identified KupA and KupB, which belong to the Kup/HAK/KT family, as novel c-di-AMP binding proteins. Both proteins are high-affinity Potassium transporters, and their transport activities are inhibited by binding of c-di-AMP. Thus, in addition to the well-studied Ktr/Trk Potassium channels, KupA and KupB represent a second class of Potassium transporters that are subject to inhibition by c-di-AMP. IMPORTANCE Potassium is an essential ion in every living cell. Even though Potassium is the most abundant cation in cells, its accumulation can be toxic. Therefore, the level of Potassium has to be tightly controlled. In many Gram-positive bacteria, the second messenger cyclic di-AMP plays a key role in the control of Potassium Homeostasis by binding to Potassium transporters and regulatory proteins and RNA molecules. In the lactic acid bacterium Lactococcus lactis, none of these conserved c-di-AMP-responsive molecules are present. In this study, we demonstrate that the KupA and KupB proteins of L. lactis IL1403 are high-affinity Potassium transporters and that their transport activity is inhibited by the second messenger c-di-AMP.

  • making and breaking of an essential poison the cyclases and phosphodiesterases that produce and degrade the essential second messenger cyclic di amp in bacteria
    Journal of Bacteriology, 2018
    Co-Authors: Fabian M Commichau, Jana L Heidemann, Ralf Ficner, Jorg Stulke
    Abstract:

    ABSTRACT Cyclic di-AMP is a second-messenger nucleotide that is produced by many bacteria and some archaea. Recent work has shown that c-di-AMP is unique among the signaling nucleotides, as this molecule is in many bacteria both essential on one hand and toxic upon accumulation on the other. Moreover, in bacteria, like Bacillus subtilis, c-di-AMP controls a biological process, Potassium Homeostasis, by binding both Potassium transporters and riboswitch molecules in the mRNAs that encode the Potassium transporters. In addition to the control of Potassium Homeostasis, c-di-AMP has been implicated in many cellular activities, including DNA repair, cell wall Homeostasis, osmotic adaptation, biofilm formation, central metabolism, and virulence. c-di-AMP is synthesized and degraded by diadenylate cyclases and phosphodiesterases, respectively. In the diadenylate cyclases, one type of catalytic domain, the diadenylate cyclase (DAC) domain, is coupled to various other domains that control the localization, the protein-protein interactions, and the regulation of the enzymes. The phosphodiesterases have a catalytic core that consists either of a DHH/DHHA1 or of an HD domain. Recent findings on the occurrence, domain organization, activity control, and structural features of diadenylate cyclases and phosphodiesterases are discussed in this review.

  • coping with an essential poison a genetic suppressor analysis corroborates a key function of c di amp in controlling Potassium ion Homeostasis in gram positive bacteria
    Journal of Bacteriology, 2018
    Co-Authors: Fabian M Commichau, Jorg Stulke
    Abstract:

    Cyclic di-AMP (c-di-AMP) is an important second messenger in bacteria. In most Firmicutes, the molecule is required for growth in complex media but also toxic upon accumulation. In an article on their current study, Zarrella and coworkers present a suppressor analysis of a Streptococcus pneumoniae strain that is unable to degrade c-di-AMP (T. M. Zarrella, D. W. Metzger, and G. Bai, J Bacteriol 200:e00045-18, 2018, https://doi.org/10.1128/JB.00045-18). Their study identifies new links between c-di-AMP and Potassium Homeostasis and supports the hypothesis that c-di-AMP serves as a second messenger to report about the intracellular Potassium concentrations.

Rolf Daniel - One of the best experts on this subject based on the ideXlab platform.

  • essentiality of c di amp in bacillus subtilis bypassing mutations converge in Potassium and glutamate Homeostasis
    PLOS Genetics, 2021
    Co-Authors: Larissa Kruger, Jan Gundlach, Christina Herzberg, Rolf Daniel, Anja Poehlein, Hermann Rath, Tiago Pedreira, Till Ischebeck, Uwe Volker, Ulrike Mader
    Abstract:

    In order to adjust to changing environmental conditions, bacteria use nucleotide second messengers to transduce external signals and translate them into a specific cellular response. Cyclic di-adenosine monophosphate (c-di-AMP) is the only known essential nucleotide second messenger. In addition to the well-established role of this second messenger in the control of Potassium Homeostasis, we observed that glutamate is as toxic as Potassium for a c-di-AMP-free strain of the Gram-positive model bacterium Bacillus subtilis. In this work, we isolated suppressor mutants that allow growth of a c-di-AMP-free strain under these toxic conditions. Characterization of glutamate resistant suppressors revealed that they contain pairs of mutations, in most cases affecting glutamate and Potassium Homeostasis. Among these mutations, several independent mutations affected a novel glutamate transporter, AimA (Amino acid importer A, formerly YbeC). This protein is the major transporter for glutamate and serine in B. subtilis. Unexpectedly, some of the isolated suppressor mutants could suppress glutamate toxicity by a combination of mutations that affect phospholipid biosynthesis and a specific gain-of-function mutation of a mechanosensitive channel of small conductance (YfkC) resulting in the acquisition of a device for glutamate export. Cultivation of the c-di-AMP-free strain on complex medium was an even greater challenge because the amounts of Potassium, glutamate, and other osmolytes are substantially higher than in minimal medium. Suppressor mutants viable on complex medium could only be isolated under anaerobic conditions if one of the two c-di-AMP receptor proteins, DarA or DarB, was absent. Also on complex medium, Potassium and osmolyte toxicity are the major bottlenecks for the growth of B. subtilis in the absence of c-di-AMP. Our results indicate that the essentiality of c-di-AMP in B. subtilis is caused by the global impact of the second messenger nucleotide on different aspects of cellular physiology.

  • essentiality of c di amp in bacillus subtilis bypassing mutations converge in Potassium and glutamate Homeostasis
    bioRxiv, 2020
    Co-Authors: Larissa Kruger, Jan Gundlach, Christina Herzberg, Rolf Daniel, Anja Poehlein, Hermann Rath, Tiago Pedreira, Uwe Volker, Ulrike Mader, Jorg Stulke
    Abstract:

    ABSTRACT In order to adjust to changing environmental conditions, bacteria use nucleotide second messengers to transduce external signals and translate them into a specific cellular response. Cyclic di-adenosine monophosphate (c-di-AMP) is the only known essential nucleotide second messenger. In addition to the well-established role of this second messenger in the control of Potassium Homeostasis, we observed that glutamate is as toxic as Potassium for a c-di-AMP-free strain of the Gram-positive model bacterium Bacillus subtilis. In this work, we isolated suppressor mutants that allow growth of a c-di-AMP-free strain under these toxic conditions. Characterization of glutamate resistant suppressors revealed that they contain pairs of mutations, in most cases affecting glutamate and Potassium Homeostasis. Among these mutations, several independent mutations affected a novel glutamate transporter, AimA (Amino acid importer A, formerly YbeC). This protein is the major transporter for glutamate and serine in B. subtilis. Unexpectedly, some of the isolated suppressor mutants could suppress glutamate toxicity by a combination of mutations that affect phospholipid biosynthesis and a specific gain-of-function mutation of a mechanosensitive channel of small conductance (YfkC) suggesting the acquisition of a device for glutamate export. Cultivation of the c-di-AMP-free strain on complex medium was an even greater challenge because the amounts of Potassium, glutamate, and other osmolytes are substantially higher than in minimal mediu. Suppressor mutants viable on complex medium could only be isolated under anaerobic conditions if one of the two c-di-AMP receptor proteins, DarA or DarB, was absent. Also on complex medium, Potassium and osmolyte toxicity are the major bottlenecks for the growth of B. subtilis in the absence of c-di-AMP. Our results indicate that the essentiality of c-di-AMP in B. subtilis is caused by the global impact of the second messenger nucleotide on different aspects of cellular physiology. AUTHOR SUMMARY Bacteria are exposed to constantly changing environmental conditions. In order to respond to these changes, they use nucleotide second messengers to transduce external signals and translate them into a specific cellular response. Among the repertoire of bacterial second messenger nucleotides, cyclic di-AMP (c-di-AMP) stands out as it is the only second messenger that is essential for the bacteria that produce it, including the Gram-positive model organism Bacillus subtilis. C-di-AMP plays a major role in the control of Potassium Homeostasis, and we found that glutamate is toxic to a B. subtilis strain lacking c-di-AMP to the same extent as Potassium. These toxic conditions were the starting point for an extensive suppressor analysis, which led to the identification of a novel glutamate transporter (AimA). If the B. subtilis strain lacking c-di-AMP was cultivated on complex medium, the isolation of suppressor mutants was only possible under anaerobic conditions and if either of the two c-di-AMP-binding signal transduction proteins was absent. This suggests that these proteins are a major burden for the cell on complex medium in their c-di-AMP free state. Our result underline the complexity of c-di-AMP signaling and propose new directions for research.

  • sustained sensing in Potassium Homeostasis cyclic di amp controls Potassium uptake by kima at the levels of expression and activity
    Journal of Biological Chemistry, 2019
    Co-Authors: Jan Gundlach, Christina Herzberg, Dietrich Hertel, Rolf Daniel, Larissa Kruger, Asan Turdiev, Anja Poehlein, Igor Tascon, Martin Weiss, Inga Hanelt
    Abstract:

    The signaling nucleotide cyclic di-AMP (c-di-AMP) is the only known essential second messenger in bacteria. Recently, c-di-AMP has been identified as being essential for controlling Potassium uptake in the model organism Bacillus subtilis and several other bacteria. A B. subtilis strain lacking c-di-AMP is not viable at high Potassium concentrations, unless the bacteria acquire suppressor mutations. In this study, we isolated such suppressor mutants and found mutations that reduced the activities of the Potassium transporters KtrCD and KimA. Although c-di-AMP–mediated control of KtrCD has previously been demonstrated, it is unknown how c-di-AMP affects KimA activity. Using the DRaCALA screening assay, we tested for any interactions of KimA and other potential target proteins in B. subtilis with c-di-AMP. This assay identified KimA, as well as the K+/H+ antiporter KhtT, the Potassium exporter CpaA (YjbQ), the osmoprotectant transporter subunit OpuCA, the primary Mg2+ importer MgtE, and DarB (YkuL), a protein of unknown function, as bona fide c-di-AMP–binding proteins. Further, binding of c-di-AMP to KimA inhibited Potassium uptake. Our results indicate that c-di-AMP controls KimA-mediated Potassium transport at both kimA gene expression and KimA activity levels. Moreover, the discovery that Potassium exporters are c-di-AMP targets indicates that this second messenger controls Potassium Homeostasis in B. subtilis at a global level by binding to riboswitches and to different classes of transport proteins involved in Potassium uptake and export.

  • control of Potassium Homeostasis is an essential function of the second messenger cyclic di amp in bacillus subtilis
    Science Signaling, 2017
    Co-Authors: Jan Gundlach, Christina Herzberg, Volkhard Kaever, Katrin Gunka, Tamara Hoffmann, Martin Weis, Johannes Gibhardt, Andrea Thurmer, Dietrich Hertel, Rolf Daniel
    Abstract:

    The second messenger cyclic di-adenosine monophosphate (c-di-AMP) is essential in the Gram-positive model organism Bacillus subtilis and in related pathogenic bacteria. It controls the activity of the conserved ydaO riboswitch and of several proteins involved in Potassium (K+) uptake. We found that the YdaO protein was conserved among several different bacteria and provide evidence that YdaO functions as a K+ transporter. Thus, we renamed the gene and protein KimA (K+ importer A). Reporter activity assays indicated that expression beyond the c-di-AMP-responsive riboswitch of the kimA upstream regulatory region occurred only in bacteria grown in medium containing low K+ concentrations. Furthermore, mass spectrometry analysis indicated that c-di-AMP accumulated in bacteria grown in the presence of high K+ concentrations but not in low concentrations. A bacterial strain lacking all genes encoding c-di-AMP-synthesizing enzymes was viable when grown in medium containing low K+ concentrations, but not at higher K+ concentrations unless it acquired suppressor mutations in the gene encoding the cation exporter NhaK. Thus, our results indicated that the control of Potassium Homeostasis is an essential function of c-di-AMP.

Nuria M Pastorsoler - One of the best experts on this subject based on the ideXlab platform.

  • collecting duct intercalated cell function and regulation
    Clinical Journal of The American Society of Nephrology, 2015
    Co-Authors: Ankita Roy, Mohammad M Albataineh, Nuria M Pastorsoler
    Abstract:

    Intercalated cells are kidney tubule epithelial cells with important roles in the regulation of acid-base Homeostasis. However, in recent years the understanding of the function of the intercalated cell has become greatly enhanced and has shaped a new model for how the distal segments of the kidney tubule integrate salt and water reabsorption, Potassium Homeostasis, and acid-base status. These cells appear in the late distal convoluted tubule or in the connecting segment, depending on the species. They are most abundant in the collecting duct, where they can be detected all the way from the cortex to the initial part of the inner medulla. Intercalated cells are interspersed among the more numerous segment-specific principal cells. There are three types of intercalated cells, each having distinct structures and expressing different ensembles of transport proteins that translate into very different functions in the processing of the urine. This review includes recent findings on how intercalated cells regulate their intracellular milieu and contribute to acid-base regulation and sodium, chloride, and Potassium Homeostasis, thus highlighting their potential role as targets for the treatment of hypertension. Their novel regulation by paracrine signals in the collecting duct is also discussed. Finally, this article addresses their role as part of the innate immune system of the kidney tubule.

  • collecting duct intercalated cell function and
    2015
    Co-Authors: Ankita Roy, Mohammad M Albataineh, Nuria M Pastorsoler
    Abstract:

    Intercalatedcellsarekidneytubuleepithelialcellswithimportantrolesintheregulationofacid-baseHomeostasis. However, in recent years the understanding of the function of the intercalated cell has become greatly enhanced and has shaped a new model for how the distal segments of the kidney tubule integrate salt and water reabsorption, Potassium Homeostasis, and acid-base status. These cells appear in the late distal convoluted tubule or in the connecting segment, depending on the species. They are most abundant in the collecting duct, where they can be detected all the way from the cortex to the initial part of the inner medulla. Intercalated cells are interspersed among the more numerous segment-specific principal cells. There are three types of intercalated cells, each having distinct structures and expressing different ensembles of transport proteins that translate into very different functions in the processing of the urine. This review includes recent findings on how intercalated cells regulate their intracellular milieu and contribute to acid-base regulation and sodium, chloride, and Potassium Homeostasis, thus highlighting their potential role as targets for the treatment of hypertension. Their novelregulationbyparacrinesignalsinthecollectingductisalsodiscussed.Finally,thisarticleaddressestheirrole as part of the innate immune system of the kidney tubule. Clin J Am Soc Nephrol 10: ccc–ccc, 2015. doi: 10.2215/CJN.08880914

Jan Gundlach - One of the best experts on this subject based on the ideXlab platform.

  • essentiality of c di amp in bacillus subtilis bypassing mutations converge in Potassium and glutamate Homeostasis
    PLOS Genetics, 2021
    Co-Authors: Larissa Kruger, Jan Gundlach, Christina Herzberg, Rolf Daniel, Anja Poehlein, Hermann Rath, Tiago Pedreira, Till Ischebeck, Uwe Volker, Ulrike Mader
    Abstract:

    In order to adjust to changing environmental conditions, bacteria use nucleotide second messengers to transduce external signals and translate them into a specific cellular response. Cyclic di-adenosine monophosphate (c-di-AMP) is the only known essential nucleotide second messenger. In addition to the well-established role of this second messenger in the control of Potassium Homeostasis, we observed that glutamate is as toxic as Potassium for a c-di-AMP-free strain of the Gram-positive model bacterium Bacillus subtilis. In this work, we isolated suppressor mutants that allow growth of a c-di-AMP-free strain under these toxic conditions. Characterization of glutamate resistant suppressors revealed that they contain pairs of mutations, in most cases affecting glutamate and Potassium Homeostasis. Among these mutations, several independent mutations affected a novel glutamate transporter, AimA (Amino acid importer A, formerly YbeC). This protein is the major transporter for glutamate and serine in B. subtilis. Unexpectedly, some of the isolated suppressor mutants could suppress glutamate toxicity by a combination of mutations that affect phospholipid biosynthesis and a specific gain-of-function mutation of a mechanosensitive channel of small conductance (YfkC) resulting in the acquisition of a device for glutamate export. Cultivation of the c-di-AMP-free strain on complex medium was an even greater challenge because the amounts of Potassium, glutamate, and other osmolytes are substantially higher than in minimal medium. Suppressor mutants viable on complex medium could only be isolated under anaerobic conditions if one of the two c-di-AMP receptor proteins, DarA or DarB, was absent. Also on complex medium, Potassium and osmolyte toxicity are the major bottlenecks for the growth of B. subtilis in the absence of c-di-AMP. Our results indicate that the essentiality of c-di-AMP in B. subtilis is caused by the global impact of the second messenger nucleotide on different aspects of cellular physiology.

  • essentiality of c di amp in bacillus subtilis bypassing mutations converge in Potassium and glutamate Homeostasis
    bioRxiv, 2020
    Co-Authors: Larissa Kruger, Jan Gundlach, Christina Herzberg, Rolf Daniel, Anja Poehlein, Hermann Rath, Tiago Pedreira, Uwe Volker, Ulrike Mader, Jorg Stulke
    Abstract:

    ABSTRACT In order to adjust to changing environmental conditions, bacteria use nucleotide second messengers to transduce external signals and translate them into a specific cellular response. Cyclic di-adenosine monophosphate (c-di-AMP) is the only known essential nucleotide second messenger. In addition to the well-established role of this second messenger in the control of Potassium Homeostasis, we observed that glutamate is as toxic as Potassium for a c-di-AMP-free strain of the Gram-positive model bacterium Bacillus subtilis. In this work, we isolated suppressor mutants that allow growth of a c-di-AMP-free strain under these toxic conditions. Characterization of glutamate resistant suppressors revealed that they contain pairs of mutations, in most cases affecting glutamate and Potassium Homeostasis. Among these mutations, several independent mutations affected a novel glutamate transporter, AimA (Amino acid importer A, formerly YbeC). This protein is the major transporter for glutamate and serine in B. subtilis. Unexpectedly, some of the isolated suppressor mutants could suppress glutamate toxicity by a combination of mutations that affect phospholipid biosynthesis and a specific gain-of-function mutation of a mechanosensitive channel of small conductance (YfkC) suggesting the acquisition of a device for glutamate export. Cultivation of the c-di-AMP-free strain on complex medium was an even greater challenge because the amounts of Potassium, glutamate, and other osmolytes are substantially higher than in minimal mediu. Suppressor mutants viable on complex medium could only be isolated under anaerobic conditions if one of the two c-di-AMP receptor proteins, DarA or DarB, was absent. Also on complex medium, Potassium and osmolyte toxicity are the major bottlenecks for the growth of B. subtilis in the absence of c-di-AMP. Our results indicate that the essentiality of c-di-AMP in B. subtilis is caused by the global impact of the second messenger nucleotide on different aspects of cellular physiology. AUTHOR SUMMARY Bacteria are exposed to constantly changing environmental conditions. In order to respond to these changes, they use nucleotide second messengers to transduce external signals and translate them into a specific cellular response. Among the repertoire of bacterial second messenger nucleotides, cyclic di-AMP (c-di-AMP) stands out as it is the only second messenger that is essential for the bacteria that produce it, including the Gram-positive model organism Bacillus subtilis. C-di-AMP plays a major role in the control of Potassium Homeostasis, and we found that glutamate is toxic to a B. subtilis strain lacking c-di-AMP to the same extent as Potassium. These toxic conditions were the starting point for an extensive suppressor analysis, which led to the identification of a novel glutamate transporter (AimA). If the B. subtilis strain lacking c-di-AMP was cultivated on complex medium, the isolation of suppressor mutants was only possible under anaerobic conditions and if either of the two c-di-AMP-binding signal transduction proteins was absent. This suggests that these proteins are a major burden for the cell on complex medium in their c-di-AMP free state. Our result underline the complexity of c-di-AMP signaling and propose new directions for research.

  • sustained sensing in Potassium Homeostasis cyclic di amp controls Potassium uptake by kima at the levels of expression and activity
    Journal of Biological Chemistry, 2019
    Co-Authors: Jan Gundlach, Christina Herzberg, Dietrich Hertel, Rolf Daniel, Larissa Kruger, Asan Turdiev, Anja Poehlein, Igor Tascon, Martin Weiss, Inga Hanelt
    Abstract:

    The signaling nucleotide cyclic di-AMP (c-di-AMP) is the only known essential second messenger in bacteria. Recently, c-di-AMP has been identified as being essential for controlling Potassium uptake in the model organism Bacillus subtilis and several other bacteria. A B. subtilis strain lacking c-di-AMP is not viable at high Potassium concentrations, unless the bacteria acquire suppressor mutations. In this study, we isolated such suppressor mutants and found mutations that reduced the activities of the Potassium transporters KtrCD and KimA. Although c-di-AMP–mediated control of KtrCD has previously been demonstrated, it is unknown how c-di-AMP affects KimA activity. Using the DRaCALA screening assay, we tested for any interactions of KimA and other potential target proteins in B. subtilis with c-di-AMP. This assay identified KimA, as well as the K+/H+ antiporter KhtT, the Potassium exporter CpaA (YjbQ), the osmoprotectant transporter subunit OpuCA, the primary Mg2+ importer MgtE, and DarB (YkuL), a protein of unknown function, as bona fide c-di-AMP–binding proteins. Further, binding of c-di-AMP to KimA inhibited Potassium uptake. Our results indicate that c-di-AMP controls KimA-mediated Potassium transport at both kimA gene expression and KimA activity levels. Moreover, the discovery that Potassium exporters are c-di-AMP targets indicates that this second messenger controls Potassium Homeostasis in B. subtilis at a global level by binding to riboswitches and to different classes of transport proteins involved in Potassium uptake and export.

  • control of Potassium Homeostasis is an essential function of the second messenger cyclic di amp in bacillus subtilis
    Science Signaling, 2017
    Co-Authors: Jan Gundlach, Christina Herzberg, Volkhard Kaever, Katrin Gunka, Tamara Hoffmann, Martin Weis, Johannes Gibhardt, Andrea Thurmer, Dietrich Hertel, Rolf Daniel
    Abstract:

    The second messenger cyclic di-adenosine monophosphate (c-di-AMP) is essential in the Gram-positive model organism Bacillus subtilis and in related pathogenic bacteria. It controls the activity of the conserved ydaO riboswitch and of several proteins involved in Potassium (K+) uptake. We found that the YdaO protein was conserved among several different bacteria and provide evidence that YdaO functions as a K+ transporter. Thus, we renamed the gene and protein KimA (K+ importer A). Reporter activity assays indicated that expression beyond the c-di-AMP-responsive riboswitch of the kimA upstream regulatory region occurred only in bacteria grown in medium containing low K+ concentrations. Furthermore, mass spectrometry analysis indicated that c-di-AMP accumulated in bacteria grown in the presence of high K+ concentrations but not in low concentrations. A bacterial strain lacking all genes encoding c-di-AMP-synthesizing enzymes was viable when grown in medium containing low K+ concentrations, but not at higher K+ concentrations unless it acquired suppressor mutations in the gene encoding the cation exporter NhaK. Thus, our results indicated that the control of Potassium Homeostasis is an essential function of c-di-AMP.