1
|
Lee SK, Occhipinti R, Moss FJ, Parker MD, Grichtchenko II, Boron WF. Distinguishing among HCO 3- , CO 3= , and H + as Substrates of Proteins That Appear To Be "Bicarbonate" Transporters. J Am Soc Nephrol 2023; 34:40-54. [PMID: 36288904 PMCID: PMC10103014 DOI: 10.1681/asn.2022030289] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 07/23/2022] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Differentiating among HCO 3- , CO 3= , and H + movements across membranes has long seemed impossible. We now seek to discriminate unambiguously among three alternate mechanisms: the inward flux of 2 HCO 3- (mechanism 1), the inward flux of 1 CO 3= (mechanism 2), and the CO 2 /HCO 3- -stimulated outward flux of 2 H + (mechanism 3). METHODS As a test case, we use electrophysiology and heterologous expression in Xenopus oocytes to examine SLC4 family members that appear to transport "bicarbonate" ("HCO 3- "). RESULTS First, we note that cell-surface carbonic anhydrase should catalyze the forward reaction CO 2 +OH - →HCO 3- if HCO 3- is the substrate; if it is not, the reverse reaction should occur. Monitoring changes in cell-surface pH ( Δ pH S ) with or without cell-surface carbonic anhydrase, we find that the presumed Cl-"HCO 3 " exchanger AE1 (SLC4A1) does indeed transport HCO 3- (mechanism 1) as long supposed, whereas the electrogenic Na/"HCO 3 " cotransporter NBCe1 (SLC4A4) and the electroneutral Na + -driven Cl-"HCO 3 " exchanger NDCBE (SLC4A8) do not. Second, we use mathematical simulations to show that each of the three mechanisms generates unique quantities of H + at the cell surface (measured as Δ pH S ) per charge transported (measured as change in membrane current, ΔIm ). Calibrating ΔpH S /Δ Im in oocytes expressing the H + channel H V 1, we find that our NBCe1 data align closely with predictions of CO 3= transport (mechanism 2), while ruling out HCO 3- (mechanism 1) and CO 2 /HCO 3- -stimulated H + transport (mechanism 3). CONCLUSIONS Our surface chemistry approach makes it possible for the first time to distinguish among HCO 3- , CO 3= , and H + fluxes, thereby providing insight into molecular actions of clinically relevant acid-base transporters and carbonic-anhydrase inhibitors.
Collapse
Affiliation(s)
- Seong-Ki Lee
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Rossana Occhipinti
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Fraser J. Moss
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Mark D. Parker
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
- Department of Physiology and Biophysics, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York
| | | | - Walter F. Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio
| |
Collapse
|
2
|
Sun H, Xu X, Luo J, Ma T, Cui J, Liu M, Xiong B, Zhu S, Liu JY. Mechanisms of PiT2-loop7 Missense Mutations Induced Pi Dyshomeostasis. Neurosci Bull 2023; 39:57-68. [PMID: 35713844 PMCID: PMC9849530 DOI: 10.1007/s12264-022-00893-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Accepted: 04/14/2022] [Indexed: 01/25/2023] Open
Abstract
PiT2 is an inorganic phosphate (Pi) transporter whose mutations are linked to primary familial brain calcification (PFBC). PiT2 mainly consists of two ProDom (PD) domains and a large intracellular loop region (loop7). The PD domains are crucial for the Pi transport, but the role of PiT2-loop7 remains unclear. In PFBC patients, mutations in PiT2-loop7 are mainly nonsense or frameshift mutations that probably cause PFBC due to C-PD1131 deletion. To date, six missense mutations have been identified in PiT2-loop7; however, the mechanisms by which these mutations cause PFBC are poorly understood. Here, we found that the p.T390A and p.S434W mutations in PiT2-loop7 decreased the Pi transport activity and cell surface levels of PiT2. Furthermore, we showed that these two mutations attenuated its membrane localization by affecting adenosine monophosphate-activated protein kinase (AMPK)- or protein kinase B (AKT)-mediated PiT2 phosphorylation. In contrast, the p.S121C and p.S601W mutations in the PD domains did not affect PiT2 phosphorylation but rather impaired its substrate-binding abilities. These results suggested that missense mutations in PiT2-loop7 can cause Pi dyshomeostasis by affecting the phosphorylation-regulated cell-surface localization of PiT2. This study helps understand the pathogenesis of PFBC caused by PiT2-loop7 missense mutations and indicates that increasing the phosphorylation levels of PiT2-loop7 could be a promising strategy for developing PFBC therapies.
Collapse
Affiliation(s)
- Hao Sun
- College of Life Science and Technology, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Xuan Xu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Junyu Luo
- College of Life Science and Technology, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Tingbin Ma
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Jiaming Cui
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Mugen Liu
- College of Life Science and Technology, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Bo Xiong
- Department of Forensic Medicine, Tongji Medical College, HUST, Wuhan, 430030, China
| | - Shujia Zhu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China.
| | - Jing-Yu Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China.
| |
Collapse
|
3
|
Wang J, Zahra A, Wang Y, Wu J. Understanding the Physiological Role of Electroneutral Na+-Coupled HCO3− Cotransporter and Its Therapeutic Implications. Pharmaceuticals (Basel) 2022; 15:ph15091082. [PMID: 36145304 PMCID: PMC9505461 DOI: 10.3390/ph15091082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 08/28/2022] [Accepted: 08/29/2022] [Indexed: 11/16/2022] Open
Abstract
Acid–base homeostasis is critical for proper physiological function and pathology. The SLC4 family of HCO3− transmembrane cotransporters is one of the HCO3− transmembrane transport carriers responsible for cellular pH regulation and the uptake or secretion of HCO3− in epithelial cells. NBCn1 (SLC4A7), an electroneutral Na+/HCO3− cotransporter, is extensively expressed in several tissues and functions as a cotransporter for net acid extrusion after cellular acidification. However, the expression and activity level of NBCn1 remain elusive. In addition, NBCn1 has been involved in numerous other cellular processes such as cell volume, cell death/survival balance, transepithelial transport, as well as regulation of cell viability. This review aims to give an inclusive overview of the most recent advances in the research of NBCn1, emphasizing the basic features, regulation, and tissue-specific physiology as well as the development and application of potent inhibitors of NBCn1 transporter in cancer therapy. Research and development of targeted therapies should be carried out for NBCn1 and its associated pathways.
Collapse
Affiliation(s)
- Jingjing Wang
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
| | - Aqeela Zahra
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
| | - YunFu Wang
- Hubei Key Laboratory of Embryonic Stem Cell Research, Hubei University of Medicine, Shiyan 442000, China
| | - Jianping Wu
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
- Hubei Key Laboratory of Embryonic Stem Cell Research, Hubei University of Medicine, Shiyan 442000, China
- Correspondence:
| |
Collapse
|
4
|
Choi I, Beedholm K, Dam VS, Bae SH, Noble DJ, Garraway SM, Aalkjaer C, Boedtkjer E. Sodium bicarbonate cotransporter NBCn1/Slc4a7 affects locomotor activity and hearing in mice. Behav Brain Res 2020; 401:113065. [PMID: 33321164 PMCID: PMC9069564 DOI: 10.1016/j.bbr.2020.113065] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 11/19/2020] [Accepted: 12/08/2020] [Indexed: 02/06/2023]
Abstract
Despite a widespread expression pattern in the central nervous system, the role of the sodium bicarbonate cotransporter NBCn1/Slc4a7 has not been investigated for locomotor activity, emotion and cognition. Here, we addressed the behavioral consequences of NBCn1 knockout and evaluated hearing and vision that are reportedly impaired in an earlier line of NBCn1 knockout mice and may contribute to behavioral changes. In a circular open field, the knockout mice traveled a shorter distance, especially in the periphery of the chamber, than wildtype littermates. The knockout mice also traveled a shorter total distance in a home cage-like open field. Rearing and grooming behaviors were reduced. The knockout and control mice displayed similar time spent and number of open and closed arms in the elevated plus maze test, indicating negligible change in anxiety. In the Morris water maze test, both groups of mice learned the location of an escape platform within comparable time on the training trials and showed similar platform identification on the probe trial. The knockout mice maintained normal visual responses in the optokinetic drum and produced evoked potentials in response to light stimuli. However, these mice failed to produce auditory evoked potentials. qPCR revealed a robust expression of an alternatively transcribed NBCn1 variant in the knockout mouse retina. These results indicate that NBCn1 deletion leads to reduced locomotor activity in mice by affecting their exploratory behaviors or emotionality. The deletion also causes hearing loss, but its effect on vision varies between different lines of knockout mice.
Collapse
Affiliation(s)
- Inyeong Choi
- Department of Physiology, Emory University School of Medicine, Atlanta, USA.
| | | | - Vibeke S Dam
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Seong-Ho Bae
- Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, USA
| | - Donald J Noble
- Department of Physiology, Emory University School of Medicine, Atlanta, USA
| | - Sandra M Garraway
- Department of Physiology, Emory University School of Medicine, Atlanta, USA
| | | | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| |
Collapse
|
5
|
Wang JL, Wang XY, Wang DK, Parker MD, Musa-Aziz R, Popple J, Guo YM, Min TX, Xia T, Tan M, Liu Y, Boron WF, Chen LM. Multiple acid-base and electrolyte disturbances upregulate NBCn1, NBCn2, IRBIT and L-IRBIT in the mTAL. J Physiol 2020; 598:3395-3415. [PMID: 32359081 DOI: 10.1113/jp279009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 04/22/2020] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS The roles of the Na+ /HCO3 - cotransporters NBCn1 and NBCn2 as well as their activators IRBIT and L-IRBIT in the regulation of the mTAL transport of NH4 + , HCO3 - , and NaCl are investigated. Dietary challenges of NH4 Cl, NaHCO3 or NaCl all increase the abundance of NBCn1 and NBCn2 in the outer medulla. The three challenges generally produce parallel increases in the abundance of IRBIT and L-IRBIT in the outer medulla. Both IRBIT and L-IRBIT powerfully stimulate the activities of the mTAL isoforms of NBCn1 and NBCn2 as expressed in Xenopus oocytes. Our findings support the hypothesis that NBCn1, NBCn2, IRBIT and L-IRBIT appropriately promote NH4 + shunting but oppose HCO3 - and NaCl reabsorption in the mTAL, and thus are at the nexus of the regulation pathways for multiple renal transport processes. ABSTRACT The medullary thick ascending limb (mTAL) plays a key role in urinary acid and NaCl excretion. NBCn1 and NBCn2 are present in the basolateral mTAL, where NBCn1 promotes NH4 + shunting. IRBIT and L-IRBIT (the IRBITs) are two powerful activators of certain acid-base transporters. Here we use western blotting and immunofluorescence to examine the effects of multiple acid-base and electrolyte disturbances on expression of NBCn1, NBCn2 and the IRBITs in rat kidney. We also use electrophysiology to examine the functional effects of IRBITs on NBCn1 and NBCn2 in Xenopus oocytes. NH4 Cl-induced metabolic acidosis (MAc) substantially increases protein expression of NBCn1 and NBCn2 in the outer medulla (OM) of rat kidney. Surprisingly, NaHCO3 -induced metabolic alkalosis (MAlk) and high-salt diet (HSD) also increase expression of NBCn1 and NBCn2 (effect of NaHCO3 > HSD). Moreover, all three challenges generally increase OM expression of the IRBITs. In Xenopus oocytes, the IRBITs substantially increase the activities of NBCn1 and NBCn2. We propose that upregulation of basolateral NBCn1 and NBCn2 plus the IRBITs in the mTAL: (1) promotes NH4 + shunting by increasing basolateral HCO3 - uptake to neutralize apical NH4 + uptake during MAc; (2) inhibits HCO3 - reabsorption during MAlk by opposing HCO3 - efflux via the basolateral anion exchanger AE2; and (3) inhibits NaCl reabsorption by mediating (with AE2) net NaCl backflux into the mTAL cell during HSD. Thus, NBCn1, NBCn2 and the IRBITs are at the nexus of the regulatory pathways for multiple renal transport processes.
Collapse
Affiliation(s)
- Jin-Lin Wang
- Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science & Technology, Huazhong University of Science & Technology, Wuhan, Hubei, 430074, China
| | - Xiao-Yu Wang
- Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science & Technology, Huazhong University of Science & Technology, Wuhan, Hubei, 430074, China
| | - Deng-Ke Wang
- Department of Physiology and Biophysics, Department of Medicine, Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Mark D Parker
- Department of Physiology and Biophysics, Department of Medicine, Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA.,Department of Physiology and Biophysics, School of Medicine, University at Buffalo: The State University of New York, Buffalo, NY, 14214, USA
| | - Raif Musa-Aziz
- Department of Physiology and Biophysics, Department of Medicine, Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA.,Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, 05508-900, Brazil
| | - Jacob Popple
- Department of Physiology and Biophysics, Department of Medicine, Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Yi-Min Guo
- Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science & Technology, Huazhong University of Science & Technology, Wuhan, Hubei, 430074, China
| | - Tian-Xin Min
- Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science & Technology, Huazhong University of Science & Technology, Wuhan, Hubei, 430074, China
| | - Tian Xia
- Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science & Technology, Huazhong University of Science & Technology, Wuhan, Hubei, 430074, China
| | - Min Tan
- School of Optical & Electronic Information, Huazhong University of Science & Technology, Wuhan, 430074, China.,Wuhan National Laboratory of Optoelectronics, Wuhan, 430074, China
| | - Ying Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science & Technology, Huazhong University of Science & Technology, Wuhan, Hubei, 430074, China
| | - Walter F Boron
- Department of Physiology and Biophysics, Department of Medicine, Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Li-Ming Chen
- Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science & Technology, Huazhong University of Science & Technology, Wuhan, Hubei, 430074, China
| |
Collapse
|
6
|
Wang JL, Zhao L, Zhu J, Wang DK, Ren MJ, Wang M, Liu Y, Boron WF, Chen LM. Expression, Localization, and Effect of High Salt Intake on Electroneutral Na +/HCO 3 - Cotransporter NBCn2 in Rat Small Intestine: Implication in Intestinal NaCl Absorption. Front Physiol 2019; 10:1334. [PMID: 31736772 PMCID: PMC6828735 DOI: 10.3389/fphys.2019.01334] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 10/07/2019] [Indexed: 12/20/2022] Open
Abstract
The electroneutral Na+/HCO3 - cotransporter NBCn2 (SLC4A10) of solute carrier family 4 (SLC4) plays important physiological and pathological roles in the body. Our previous study showed that NBCn2 is expressed on the protein level in the small intestine of rat. Here, by reverse-transcription polymerase chain reaction (PCR), we identified a novel full-length NBCn2 variant, i.e., NBCn2-K, from rat small intestine. By pHi measurement with Xenopus oocytes, the activity of NBCn2-K is not significantly different from NBCn2-G. By western blotting, NBCn2 and the Na+/H+ exchanger NHE3 (SLC9A3) are predominantly expressed in the jejunum of rat small intestine. By immunofluorescence, NBCn2 and NHE3 are localized at the apical domain of the jejunum. NaCl overload decreases the expression of NBCn2 by 56% and that of NHE3 by 40% in the small intestine. We propose that NBCn2 is involved in the transepithelial NaCl absorption in the small intestine, and that the down-regulation of NBCn2 by NaCl represents an adaptive response to high salt intake in rat.
Collapse
Affiliation(s)
- Jin-Lin Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Lei Zhao
- Department of Obstetrics, Maternal and Child Health Hospital of Hubei Province, Wuhan, China
| | - Jun Zhu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Deng-Ke Wang
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Mei-Juan Ren
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Meng Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Ying Liu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Walter F. Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Li-Ming Chen
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| |
Collapse
|
7
|
Sedlyarov V, Eichner R, Girardi E, Essletzbichler P, Goldmann U, Nunes-Hasler P, Srndic I, Moskovskich A, Heinz LX, Kartnig F, Bigenzahn JW, Rebsamen M, Kovarik P, Demaurex N, Superti-Furga G. The Bicarbonate Transporter SLC4A7 Plays a Key Role in Macrophage Phagosome Acidification. Cell Host Microbe 2018; 23:766-774.e5. [PMID: 29779931 PMCID: PMC6002608 DOI: 10.1016/j.chom.2018.04.013] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 03/14/2018] [Accepted: 04/19/2018] [Indexed: 12/11/2022]
Abstract
Macrophages represent the first line of immune defense against pathogens, and phagosome acidification is a necessary step in pathogen clearance. Here, we identified the bicarbonate transporter SLC4A7, which is strongly induced upon macrophage differentiation, as critical for phagosome acidification. Loss of SLC4A7 reduced acidification of phagocytosed beads or bacteria and impaired the intracellular microbicidal capacity in human macrophage cell lines. The phenotype was rescued by wild-type SLC4A7, but not by SLC4A7 mutants, affecting transport capacity or cell surface localization. Loss of SLC4A7 resulted in increased cytoplasmic acidification during phagocytosis, suggesting that SLC4A7-mediated, bicarbonate-driven maintenance of cytoplasmic pH is necessary for phagosome acidification. Altogether, we identify SLC4A7 and bicarbonate-driven cytoplasmic pH homeostasis as an important element of phagocytosis and the associated microbicidal functions in macrophages. CRISPR screen identifies SLC4A7 to be required for phagosome acidification Intracellular bacterial killing by macrophages is impaired in absence of SLC4A7 Bicarbonate transport activity of SLC4A7 is required for phagosome acidification SLC4A7 regulates phagosome acidification via homeostatic control of cytoplasmic pH
Collapse
Affiliation(s)
- Vitaly Sedlyarov
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Ruth Eichner
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Enrico Girardi
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Patrick Essletzbichler
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Ulrich Goldmann
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Paula Nunes-Hasler
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva 1211, Switzerland
| | - Ismet Srndic
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Anna Moskovskich
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Leonhard X Heinz
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Felix Kartnig
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Johannes W Bigenzahn
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Manuele Rebsamen
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria
| | - Pavel Kovarik
- Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter (VBC), Vienna 1030, Austria
| | - Nicolas Demaurex
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva 1211, Switzerland
| | - Giulio Superti-Furga
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna 1090, Austria; Center for Physiology and Pharmacology, Medical University of Vienna, Vienna 1090, Austria.
| |
Collapse
|
8
|
Xie ZD, Guo YM, Ren MJ, Yang J, Wang SF, Xu TH, Chen LM, Liu Y. The Balance of [Formula: see text] Secretion vs. Reabsorption in the Endometrial Epithelium Regulates Uterine Fluid pH. Front Physiol 2018; 9:12. [PMID: 29422866 PMCID: PMC5788990 DOI: 10.3389/fphys.2018.00012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 01/05/2018] [Indexed: 12/26/2022] Open
Abstract
Uterine fluid contains a high concentration of HCO3- which plays an essential role in sperm capacitation and fertilization. In addition, the HCO3- concentration in uterine fluid changes periodically during the estrous cycle. It is well-known that the endometrial epithelium contains machineries involving the apical SLC26 family anion exchangers for secreting HCO3- into the uterine fluid. In the present study, we find for the first time that the electroneutral Na+/HCO3- cotransporter NBCn1 is expressed at the apical membrane of the endometrial epithelium. The protein abundance of the apical NBCn1 and that of the apical SLC26A4 and SLC26A6 are reciprocally regulated during the estrous cycle in the uterus. NBCn1 is most abundant at diestrus, whereas SLC26A4/A6 are most abundant at proestrus/estrus. In the ovariectomized mice, the expression of uterine NBCn1 is inhibited by β-estradiol, but stimulated by progesterone, whereas that of uterine SLC26A4/A6 is stimulated by β-estradiol. In vivo perfusion studies show that the endometrial epithelium is capable of both secreting and reabsorbing HCO3-. Moreover, the activity for HCO3- secretion by the endometrial epithelium is significantly higher at estrus than it is at diestrus. The opposite is true for HCO3- reabsorption. We conclude that the endometrial epithelium simultaneously contains the activity for HCO3- secretion involving the apical SLC26A4/A6 and the activity for HCO3- reabsorption involving the apical NBCn1, and that the acid-base homeostasis in the uterine fluid is regulated by the finely-tuned balance of the two activities.
Collapse
Affiliation(s)
- Zhang-Dong Xie
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Biophysics and Molecular Physiology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Yi-Min Guo
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Biophysics and Molecular Physiology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Mei-Juan Ren
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Biophysics and Molecular Physiology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Jichun Yang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Shao-Fang Wang
- Wuhan National Laboratory for Optoelectronics, Britton Chance Center for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan, China
| | - Tong-Hui Xu
- Wuhan National Laboratory for Optoelectronics, Britton Chance Center for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan, China
| | - Li-Ming Chen
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Biophysics and Molecular Physiology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Ying Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Biophysics and Molecular Physiology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| |
Collapse
|
9
|
Guo YM, Liu Y, Liu M, Wang JL, Xie ZD, Chen KJ, Wang DK, Occhipinti R, Boron WF, Chen LM. Na +/HCO 3- Cotransporter NBCn2 Mediates HCO 3- Reclamation in the Apical Membrane of Renal Proximal Tubules. J Am Soc Nephrol 2017; 28:2409-2419. [PMID: 28280139 DOI: 10.1681/asn.2016080930] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 01/23/2017] [Indexed: 12/31/2022] Open
Abstract
The kidney maintains systemic acid-base balance by reclaiming from the renal tubule lumen virtually all HCO3- filtered in glomeruli and by secreting additional H+ to titrate luminal buffers. For proximal tubules, which are responsible for about 80% of this activity, it is believed that HCO3- reclamation depends solely on H+ secretion, mediated by the apical Na+/H+ exchanger NHE3 and the vacuolar proton pump. However, NHE3 and the proton pump cannot account for all HCO3- reclamation. Here, we investigated the potential contribution of two variants of the electroneutral Na+/HCO3- cotransporter NBCn2, the amino termini of which start with the amino acids MCDL (MCDL-NBCn2) and MEIK (MEIK-NBCn2). Western blot analysis and immunocytochemistry revealed that MEIK-NBCn2 predominantly localizes at the basolateral membrane of medullary thick ascending limbs in the rat kidney, whereas MCDL-NBCn2 localizes at the apical membrane of proximal tubules. Notably, NH4Cl-induced systemic metabolic acidosis or hypokalemic alkalosis downregulated the abundance of MCDL-NBCn2 and reciprocally upregulated NHE3 Conversely, NaHCO3-induced metabolic alkalosis upregulated MCDL-NBCn2 and reciprocally downregulated NHE3 We propose that the apical membrane of the proximal tubules has two distinct strategies for HCO3- reclamation: the conventional indirect pathway, in which NHE3 and the proton pump secrete H+ to titrate luminal HCO3-, and the novel direct pathway, in which NBCn2 removes HCO3- from the lumen. The reciprocal regulation of NBCn2 and NHE3 under different physiologic conditions is consistent with our mathematical simulations, which suggest that HCO3- uptake and H+ secretion have reciprocal efficiencies for HCO3- reclamation versus titration of luminal buffers.
Collapse
Affiliation(s)
- Yi-Min Guo
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Ying Liu
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Mei Liu
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Jin-Lin Wang
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Zhang-Dong Xie
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Kang-Jing Chen
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Deng-Ke Wang
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and.,Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Rossana Occhipinti
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Li-Ming Chen
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| |
Collapse
|
10
|
Myers EJ, Marshall A, Jennings ML, Parker MD. Mouse Slc4a11 expressed in Xenopus oocytes is an ideally selective H+/OH- conductance pathway that is stimulated by rises in intracellular and extracellular pH. Am J Physiol Cell Physiol 2016; 311:C945-C959. [PMID: 27681179 PMCID: PMC5206308 DOI: 10.1152/ajpcell.00259.2016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 09/28/2016] [Indexed: 11/22/2022]
Abstract
The SLC4A11 gene encodes the bicarbonate-transporter-related protein BTR1, which is mutated in syndromes characterized by vision and hearing loss. Signs of these diseases [congenital hereditary endothelial dystrophy (CHED) and Harboyan syndrome] are evident in mouse models of Slc4a11 disruption. However, the intrinsic activity of Slc4a11 remains controversial, complicating assignment of its (patho)physiological role. Most studies concur that Slc4a11 transports H+ (or the thermodynamically equivalent species OH-) rather than HCO3-, but disparities have arisen as to whether the transport is coupled to another species such as Na+ or NH3/NH4+ Here for the first time, we examine the action of mouse Slc4a11 in Xenopus oocytes. We simultaneously monitor changes in intracellular pH, membrane potential, and conductance as we alter extracellular pH, revealing the electrical and chemical driving forces that underlie the observed ion fluxes. We find that mSlc4a11 is an ideally selective H+/OH- conductive pathway, the action of which is uncoupled from the cotransport of any other ion. We also find that the activity of mSlc4a11 is independently enhanced by both extracellular and intracellular alkalinization, suggesting OH- as the most likely substrate and providing a novel explanation for the apparent NH3-dependence of Slc4a11-mediated currents reported by others. We suggest that the unique properties of Slc4a11 action underlie its value as a pH regulator in corneal endothelial cells.
Collapse
Affiliation(s)
- Evan J Myers
- Department of Physiology and Biophysics, The State University of New York: The University at Buffalo, Buffalo, New York
| | - Aniko Marshall
- Department of Physiology and Biophysics, The State University of New York: The University at Buffalo, Buffalo, New York
| | - Michael L Jennings
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Mark D Parker
- Department of Physiology and Biophysics, The State University of New York: The University at Buffalo, Buffalo, New York;
- Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo: The State University of New York, Buffalo, New York; and
- State University of New York Eye Institutes, University at Buffalo: The State University of New York, Buffalo, New York
| |
Collapse
|
11
|
Liu Y, Yang J, Chen LM. Structure and Function of SLC4 Family [Formula: see text] Transporters. Front Physiol 2015; 6:355. [PMID: 26648873 PMCID: PMC4664831 DOI: 10.3389/fphys.2015.00355] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 11/10/2015] [Indexed: 12/12/2022] Open
Abstract
The solute carrier SLC4 family consists of 10 members, nine of which are [Formula: see text] transporters, including three Na(+)-independent Cl(-)/[Formula: see text] exchangers AE1, AE2, and AE3, five Na(+)-coupled [Formula: see text] transporters NBCe1, NBCe2, NBCn1, NBCn2, and NDCBE, as well as "AE4" whose Na(+)-dependence remains controversial. The SLC4 [Formula: see text] transporters play critical roles in pH regulation and transepithelial movement of electrolytes with a broad range of demonstrated physiological relevances. Dysfunctions of these transporters are associated with a series of human diseases. During the past decades, tremendous amount of effort has been undertaken to investigate the topological organization of the SLC4 transporters in the plasma membrane. Based upon the proposed topology models, mutational and functional studies have identified important structural elements likely involved in the ion translocation by the SLC4 transporters. In the present article, we review the advances during the past decades in understanding the structure and function of the SLC4 transporters.
Collapse
Affiliation(s)
- Ying Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Biophysics and Molecular Physiology, School of Life Science and Technology, Huazhong University of Science and TechnologyWuhan, China
| | - Jichun Yang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University Health Science CenterBeijing, China
| | - Li-Ming Chen
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Biophysics and Molecular Physiology, School of Life Science and Technology, Huazhong University of Science and TechnologyWuhan, China
| |
Collapse
|