1
|
Zhang Z, Bao YY, Zhou SH. Pump Proton and Laryngeal H +/K + ATPases. Int J Gen Med 2020; 13:1509-1514. [PMID: 33363399 PMCID: PMC7754099 DOI: 10.2147/ijgm.s284952] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 11/20/2020] [Indexed: 12/14/2022] Open
Abstract
Purpose The presence of extra-gastric H+/K+ ATPases may explain the clinically significant effect of proton pump inhibitor (PPI) pharmacotherapy in patients with chronic laryngitis related to laryngopharyngeal reflux disease (LPRD) but without gastroesophageal reflux disease (GERD) symptoms. Given the need for a better understanding of GERD and LPRD, we review the various proton pumps with respect to their classification, function, and distribution. We then consider the potential role of the laryngeal H+/K+ ATPase pump in LPRD. Methods We searched databases of PubMed, EMBASE, and Web of Science to achieve related published before September 15, 2020. Results There were only seven English-literatures meeting inclusive criteria about laryngeal H+/K+ ATPases. Some studies provide convincing evidence of a laryngeal H+/K+ ATPase in normal laryngeal tissues but also suggest the potential role of the proton pump in the abnormal mucus secretion frequently seen in patients with chronic laryngitis. Conclusion A laryngeal H+/K+ ATPase expresses in normal laryngeal tissues. These findings question the current understanding of GERD and LPRD.
Collapse
Affiliation(s)
- Zhe Zhang
- Department of Otolaryngology, Peoples Hospital of Yuyao City, Yuyao 315400, Zhejiang, People's Republic of China
| | - Yang-Yang Bao
- Department of Otolaryngology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, People's Republic of China
| | - Shui-Hong Zhou
- Department of Otolaryngology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, People's Republic of China
| |
Collapse
|
2
|
Baratta VM, Norz V, Barahona MJ, Gisinger TM, Mulligan D, Geibel JP. Penicillin G Induces H+, K+-ATPase via a Nitric Oxide-Dependent Mechanism in the Rat Colonic Crypt. Cell Physiol Biochem 2020; 54:1132-1142. [PMID: 33175479 PMCID: PMC8095381 DOI: 10.33594/000000305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2020] [Indexed: 11/21/2022] Open
Abstract
Background/Aims: The colonic H+, K+ ATPase (HKA2) is a heterodimeric membrane protein that exchanges luminal K+ for intracellular H+ and is involved in maintaining potassium homeostasis. Under homeostatic conditions, the colonic HKA2 remains inactive, since most of the potassium is absorbed by the small intestine. In diarrheal states, potassium is secreted and compensatory potassium absorption becomes necessary. This study proposes a novel mechanism whereby the addition of penicillin G sodium salt (penG) to colonic crypts stimulates potassium uptake in the presence of intracellular nitric oxide (NO), under sodium-free (0-Na+) conditions. Methods: Sprague Dawley rat colonic crypts were isolated and pHi changes were monitored through the ammonium prepulse technique. Increased proton extrusion in 0-Na+ conditions reflected heightened H+, K+ ATPase activity. Colonic crypts were exposed to penG, L-arginine (a NO precursor), and N-nitro l-arginine methyl ester (L-NAME, a NO synthase inhibitor). Results: Isolated administration of penG significantly increased H+, K+ ATPase activity from baseline, p 0.0067. Co-administration of arginine and penG in 0-Na+ conditions further upregulated H+, K+ ATPase activity, p <0.0001. Crypt perfusion with L-NAME and penG demonstrated a significant reduction in H+, K+ ATPase activity, p 0.0058. Conclusion: Overall, acute exposure of colonic crypts to penG activates the H+, K+ ATPase in the presence of NO. This study provides new insights into colonic potassium homeostasis.
Collapse
Affiliation(s)
- Vanessa M Baratta
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA
| | - Valentina Norz
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA.,Paracelsus Medical University, School of Medicine, Salzburg, Austria
| | - Maria J Barahona
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA
| | - Teresa M Gisinger
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA.,Paracelsus Medical University, School of Medicine, Salzburg, Austria
| | - David Mulligan
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA
| | - John P Geibel
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA, .,Yale University School of Medicine, Department of Cellular and Molecular Physiology, New Haven, CT, USA
| |
Collapse
|
3
|
Rehman S, Narayanan K, Nickerson AJ, Coon SD, Hoque KM, Sandle GI, Rajendran VM. Parallel intermediate conductance K + and Cl - channel activity mediates electroneutral K + exit across basolateral membranes in rat distal colon. Am J Physiol Gastrointest Liver Physiol 2020; 319:G142-G150. [PMID: 32567323 PMCID: PMC7500264 DOI: 10.1152/ajpgi.00011.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Transepithelial K+ absorption requires apical K+ uptake and basolateral K+ exit. In the colon, apical H+-K+-ATPase mediates cellular K+ uptake, and it has been suggested that electroneutral basolateral K+ exit reflects K+-Cl- cotransporter-1 (KCC1) operating in parallel with K+ and Cl- channels. The present study was designed to identify basolateral transporter(s) responsible for K+ exit in rat distal colon. Active K+ absorption was determined by measuring 86Rb+ (K+ surrogate) fluxes across colonic epithelia under voltage-clamp conditions. With zero Cl- in the mucosal solution, net K+ absorption was reduced by 38%, indicating that K+ absorption was partially Cl--dependent. Serosal addition of DIOA (KCC1 inhibitor) or Ba2+ (nonspecific K+ channel blocker) inhibited net K+ absorption by 21% or 61%, respectively, suggesting that both KCC1 and K+ channels contribute to basolateral K+ exit. Clotrimazole and TRAM34 (IK channel blockers) added serosally inhibited net K+ absorption, pointing to the involvement of IK channels in basolateral K+ exit. GaTx2 (CLC2 blocker) added serosally also inhibited net K+ absorption, suggesting that CLC2-mediated Cl- exit accompanies IK channel-mediated K+ exit across the basolateral membrane. Net K+ absorption was not inhibited by serosal addition of either IbTX (BK channel blocker), apamin (SK channel blocker), chromanol 293B (KV7 channel blocker), or CFTRinh172 (CFTR blocker). Immunofluorescence studies confirmed basolateral membrane colocalization of CLC2-like proteins and Na+-K+-ATPase α-subunits. We conclude that active K+ absorption in rat distal colon involves electroneutral basolateral K+ exit, which may reflect IK and CLC2 channels operating in parallel.NEW & NOTEWORTHY This study demonstrates that during active electroneutral K+ absorption in rat distal colon, K+ exit across the basolateral membrane mainly reflects intermediate conductance K+ channels operating in conjunction with chloride channel 2, with a smaller, but significant, contribution from K+-Cl- cotransporter-1 (KCC1) activity.
Collapse
Affiliation(s)
- Shabina Rehman
- 1Departments of Biochemistry West Virginia University School of Medicine, Morgantown, West Virginia
| | - Karthikeyan Narayanan
- 1Departments of Biochemistry West Virginia University School of Medicine, Morgantown, West Virginia
| | - Andrew J. Nickerson
- 1Departments of Biochemistry West Virginia University School of Medicine, Morgantown, West Virginia,2Departments of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, West Virginia
| | - Steven D. Coon
- 3Department of Biological Sciences, Port Peck Community College, Poplar, Montana
| | - Kazi Mirajul Hoque
- 4Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Geoffrey I. Sandle
- 5Leeds Institute for Medical Research at St. James’s, St. James’s University Hospital. Leeds, United Kingdom
| | - Vazhaikkurichi M. Rajendran
- 1Departments of Biochemistry West Virginia University School of Medicine, Morgantown, West Virginia,6Departments of Medicine, West Virginia University School of Medicine, Morgantown, West Virginia
| |
Collapse
|
4
|
Rajendran VM, Sandle GI. Colonic Potassium Absorption and Secretion in Health and Disease. Compr Physiol 2018; 8:1513-1536. [PMID: 30215859 PMCID: PMC9769410 DOI: 10.1002/cphy.c170030] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The colon has large capacities for K+ absorption and K+ secretion, but its role in maintaining K+ homeostasis is often overlooked. For many years, passive diffusion and/or solvent drag were thought to be the primary mechanisms for K+ absorption in human and animal colon. However, it is now clear that apical H+ ,K+ -ATPase, in coordination with basolateral K+ -Cl- cotransport and/or K+ and Cl- channels operating in parallel, mediate electroneutral K+ absorption in animal colon. We now know that K+ absorption in rat colon reflects ouabain-sensitive and ouabain-insensitive apical H+ ,K+ -ATPase activities. Ouabain-insensitive and ouabain-sensitive H+ ,K+ -ATPases are localized in surface and crypt cells, respectively. Colonic H+ ,K+ -ATPase consists of α- (HKCα ) and β- (HKCβ ) subunits which, when coexpressed, exhibit ouabain-insensitive H+ ,K+ -ATPase activity in HEK293 cells, while HKCα coexpressed with the gastric β-subunit exhibits ouabain-sensitive H+ ,K+ -ATPase activity in Xenopus oocytes. Aldosterone enhances apical H+ ,K+ -ATPase activity, HKCα specific mRNA and protein expression, and K+ absorption. Active K+ secretion, on the other hand, is mediated by apical K+ channels operating in a coordinated way with the basolateral Na+ -K+ -2Cl- cotransporter. Both Ca2+ -activated intermediate conductance K+ (IK) and large conductance K+ (BK) channels are located in the apical membrane of colonic epithelia. IK channel-mediated K+ efflux provides the driving force for Cl- secretion, while BK channels mediate active (e.g., cAMP-activated) K+ secretion. BK channel expression and activity are increased in patients with end-stage renal disease and ulcerative colitis. This review summarizes the role of apical H+ ,K+ -ATPase in K+ absorption, and apical BK channel function in K+ secretion in health and disease. © 2018 American Physiological Society. Compr Physiol 8:1513-1536, 2018.
Collapse
Affiliation(s)
| | - Geoffrey I. Sandle
- Leeds Institute of Biomedical and Clinical Sciences, St James’s University Hospital, Leeds LS9 7TF, UK
| |
Collapse
|
5
|
Shah VS, Meyerholz DK, Tang XX, Reznikov L, Abou Alaiwa M, Ernst SE, Karp PH, Wohlford-Lenane CL, Heilmann KP, Leidinger MR, Allen PD, Zabner J, McCray PB, Ostedgaard LS, Stoltz DA, Randak CO, Welsh MJ. Airway acidification initiates host defense abnormalities in cystic fibrosis mice. Science 2016; 351:503-7. [PMID: 26823428 DOI: 10.1126/science.aad5589] [Citation(s) in RCA: 228] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cystic fibrosis (CF) is caused by mutations in the gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel. In humans and pigs, the loss of CFTR impairs respiratory host defenses, causing airway infection. But CF mice are spared. We found that in all three species, CFTR secreted bicarbonate into airway surface liquid. In humans and pigs lacking CFTR, unchecked H(+) secretion by the nongastric H(+)/K(+) adenosine triphosphatase (ATP12A) acidified airway surface liquid, which impaired airway host defenses. In contrast, mouse airways expressed little ATP12A and secreted minimal H(+); consequently, airway surface liquid in CF and non-CF mice had similar pH. Inhibiting ATP12A reversed host defense abnormalities in human and pig airways. Conversely, expressing ATP12A in CF mouse airways acidified airway surface liquid, impaired defenses, and increased airway bacteria. These findings help explain why CF mice are protected from infection and nominate ATP12A as a potential therapeutic target for CF.
Collapse
Affiliation(s)
- Viral S Shah
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Department of Molecular Physiology and Biophysics, Pappajohn Biomedical Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - David K Meyerholz
- Department of Pathology, University of Iowa, Iowa City, IA 52242, USA
| | - Xiao Xiao Tang
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Howard Hughes Medical Institute, University of Iowa, Iowa City, IA 52242, USA
| | - Leah Reznikov
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | | | - Sarah E Ernst
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Howard Hughes Medical Institute, University of Iowa, Iowa City, IA 52242, USA
| | - Philip H Karp
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Howard Hughes Medical Institute, University of Iowa, Iowa City, IA 52242, USA
| | | | | | | | - Patrick D Allen
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Joseph Zabner
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Paul B McCray
- Department of Pediatrics University of Iowa, Iowa City, IA 52242, USA. Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
| | | | - David A Stoltz
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Department of Molecular Physiology and Biophysics, Pappajohn Biomedical Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA. Department of Biomedical Engineering, College of Engineering, University of Iowa, Iowa City, IA 52242, USA
| | | | - Michael J Welsh
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Department of Molecular Physiology and Biophysics, Pappajohn Biomedical Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA. Howard Hughes Medical Institute, University of Iowa, Iowa City, IA 52242, USA
| |
Collapse
|
6
|
Abstract
H-K-ATPase type 2 (HKA2), also known as the "nongastric" or "colonic" H-K-ATPase, is broadly expressed, and its presence in the kidney has puzzled experts in the field of renal ion transport systems for many years. One of the most important and robust characteristics of this transporter is that it is strongly stimulated after dietary K(+) restriction. This result prompted many investigators to propose that it should play a role in allowing the kidney to efficiently retain K(+) under K(+) depletion. However, the apparent absence of a clear renal phenotype in HKA2-null mice has led to the idea that this transporter is an epiphenomenon. This review summarizes past and recent findings regarding the functional, structural and physiological characteristics of H-K-ATPase type 2. The findings discussed in this review suggest that, as in the famous story, the ugly duckling of the X-K-ATPase family is actually a swan.
Collapse
Affiliation(s)
- Gilles Crambert
- INSERM/UPMC Paris 6/CNRS, Centre de Recherche des Cordeliers Génomique, Physiologie et Physiopathologie Rénales, Equipe 3 U1138, ERL 8228, 15 rue de l'Ecole de Médecine, 75270 Paris Cedex, France.
| |
Collapse
|
7
|
Codina J, Opyd TS, Powell ZB, Furdui CM, Petrovic S, Penn RB, DuBose TD. pH-dependent regulation of the α-subunit of H+-K+-ATPase (HKα2). Am J Physiol Renal Physiol 2011; 301:F536-43. [PMID: 21653633 PMCID: PMC3174558 DOI: 10.1152/ajprenal.00220.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 06/03/2011] [Indexed: 11/22/2022] Open
Abstract
The H(+)-K(+)-ATPase α-subunit (HKα(2)) participates importantly in systemic acid-base homeostasis and defends against metabolic acidosis. We have previously shown that HKα(2) plasma membrane expression is regulated by PKA (Codina J, Liu J, Bleyer AJ, Penn RB, DuBose TD Jr. J Am Soc Nephrol 17: 1833-1840, 2006) and in a separate study demonstrated that genetic ablation of the proton-sensing G(s)-coupled receptor GPR4 results in spontaneous metabolic acidosis (Sun X, Yang LV, Tiegs BC, Arend LJ, McGraw DW, Penn RB, Petrovic S. J Am Soc Nephrol 21: 1745-1755, 2010). In the present study, we investigated the ability of chronic acidosis and GPR4 to regulate HKα(2) expression in HEK-293 cells. Chronic acidosis was modeled in vitro by using multiple methods: reducing media pH by adjusting bicarbonate concentration, adding HCl, or by increasing the ambient concentration of CO(2). PKA activity and HKα(2) protein were monitored by immunoblot analysis, and HKα(2) mRNA, by real-time PCR. Chronic acidosis did not alter the expression of HKα(2) mRNA; however, PKA activity and HKα(2) protein abundance increased when media pH decreased from 7.4 to 6.8. Furthermore, this increase was independent of the method used to create chronic acidosis. Heterologous expression of GPR4 was sufficient to increase both basal and acid-stimulated PKA activity and similarly increase basal and acid-stimulated HKα(2) expression. Collectively, these results suggest that chronic acidosis and GPR4 increase HKα(2) protein by increasing PKA activity without altering HKα(2) mRNA abundance, implicating a regulatory role of pH-activated GPR4 in homeostatic regulation of HKα(2) and acid-base balance.
Collapse
Affiliation(s)
- Juan Codina
- Sections on Nephrology and Molecular Medicine, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | | | | | | | | | | | | |
Collapse
|
8
|
Shao J, Gumz ML, Cain BD, Xia SL, Shull GE, van Driel IR, Wingo CS. Pharmacological profiles of the murine gastric and colonic H,K-ATPases. Biochim Biophys Acta Gen Subj 2010; 1800:906-11. [PMID: 20594946 DOI: 10.1016/j.bbagen.2010.05.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 04/23/2010] [Accepted: 05/03/2010] [Indexed: 10/19/2022]
Abstract
BACKGROUND The H,K-ATPase, consisting of α and ß subunits, belongs to the P-type ATPase family. There are two isoforms of the α subunit, HKα₁ and HKα₂ encoded by different genes. The ouabain-resistant gastric HKα₁-H,K-ATPase is Sch28080-sensitive. However, the colonic HKα₂-H,K-ATPase from different species shows poor primary structure conservation of the HKα₂ subunit between species and diverse pharmacological sensitivity to ouabain and Sch28080. This study sought to determine the contribution of each gene to functional activity and its pharmacological profile using mouse models with targeted disruption of HKα₁, HKα₂, or HKbeta genes. METHODS Membrane vesicles from gastric mucosa and distal colon in wild-type (WT), HKα₁, HKα₂, or HKß knockout (KO) mice were extracted. K-ATPase activity and pharmacological profiles were examined. RESULTS The colonic H,K-ATPase demonstrated slightly greater affinity for K(+) than the gastric H,K-ATPase. This K-ATPase activity was not detected in the colon of HKα₂ KO but was observed in HKß KO with properties indistinguishable from WT. Neither ouabain nor Sch28080 had a significant effect on the WT colonic K-ATPase activity, but orthovanadate abolished this activity. Amiloride and its analogs benzamil and 5-N-ethyl-N-isopropylamiloride inhibited K-ATPase activity of HKα₁-containing H,K-ATPase; the dose dependence of inhibition was similar for all three inhibitors. In contrast, the colonic HKα₂-H,K-ATPase was not inhibited by these compounds. CONCLUSIONS These data demonstrate that the mouse colonic H,K-ATPase exhibits a ouabain- and Sch28080-insensitive, orthovanadate-sensitive K-ATPase activity. Interestingly, pharmacological studies suggested that the mouse gastric H,K-ATPase is sensitive to amiloride. GENERAL SIGNIFICANCE Characterization of the pharmacological profiles of the H,K-ATPases is important for understanding the relevant knockout animals and for considering the specificity of the inhibitors.
Collapse
Affiliation(s)
- Jiahong Shao
- Department of Medicine, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | | | | | | | | | | | | |
Collapse
|
9
|
Colonic potassium handling. Pflugers Arch 2010; 459:645-56. [PMID: 20143237 DOI: 10.1007/s00424-009-0781-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 12/23/2009] [Accepted: 12/25/2009] [Indexed: 10/19/2022]
Abstract
Homeostatic control of plasma K+ is a necessary physiological function. The daily dietary K+ intake of approximately 100 mmol is excreted predominantly by the distal tubules of the kidney. About 10% of the ingested K+ is excreted via the intestine. K+ handling in both organs is specifically regulated by hormones and adapts readily to changes in dietary K+ intake, aldosterone and multiple local paracrine agonists. In chronic renal insufficiency, colonic K+ secretion is greatly enhanced and becomes an important accessory K+ excretory pathway. During severe diarrheal diseases of different causes, intestinal K+ losses caused by activated ion secretion may become life threatening. This topical review provides an update of the molecular mechanisms and the regulation of mammalian colonic K+ absorption and secretion. It is motivated by recent results, which have identified the K+ secretory ion channel in the apical membrane of distal colonic enterocytes. The directed focus therefore covers the role of the apical Ca2+ and cAMP-activated BK channel (KCa1.1) as the apparently only secretory K+ channel in the distal colon.
Collapse
|
10
|
Purification and characterization of the ouabain-sensitive H+/K+-ATPase from guinea-pig distal colon. Arch Biochem Biophys 2010; 496:21-32. [PMID: 20122893 DOI: 10.1016/j.abb.2010.01.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2009] [Revised: 01/26/2010] [Accepted: 01/28/2010] [Indexed: 11/21/2022]
Abstract
Distal colon absorbs K+ through a Na+-independent, ouabain-sensitive H+/K+-exchange, associated to an apical ouabain-sensitive H+/K+-ATPase. Expression of HKalpha2, gene associated with this ATPase, induces K+-transport mechanisms, whose ouabain susceptibility is inconsistent. Both ouabain-sensitive and ouabain-insensitive K+-ATPase activities have been described in colonocytes. However, native H+/K+-ATPases have not been identified as unique biochemical entities. Herein, a procedure to purify ouabain-sensitive H+/K+-ATPase from guinea-pig distal colon is described. H+/K+-ATPase is Mg2+-dependent and activated by K+, Cs+ and NH4+ but not by Na+ or Li+, independently of K+-accompanying anion. H+/K+-ATPase was inhibited by ouabain and vanadate but insensitive to SCH-28080 and bafilomycin-A. Enzyme was phosphorylated from [32P]-gamma-ATP, forming an acyl-phosphate bond, in an Mg2+-dependent, vanadate-sensitive process. K+ inhibited phosphorylation, effect blocked by ouabain. H+/K+-ATPase is an alpha/beta-heterodimer, whose subunits, identified by Tandem-mass spectrometry, seems to correspond to HKalpha2 and Na+/K+-ATPase beta1-subunit, respectively. Thus, colonic ouabain-sensitive H+/K+-ATPase is a distinctive P-type ATPase.
Collapse
|
11
|
Gumz ML, Lynch IJ, Greenlee MM, Cain BD, Wingo CS. The renal H+-K+-ATPases: physiology, regulation, and structure. Am J Physiol Renal Physiol 2009; 298:F12-21. [PMID: 19640897 DOI: 10.1152/ajprenal.90723.2008] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The H(+)-K(+)-ATPases are ion pumps that use the energy of ATP hydrolysis to transport protons (H(+)) in exchange for potassium ions (K(+)). These enzymes consist of a catalytic alpha-subunit and a regulatory beta-subunit. There are two catalytic subunits present in the kidney, the gastric or HKalpha(1) isoform and the colonic or HKalpha(2) isoform. In this review we discuss new information on the physiological function, regulation, and structure of the renal H(+)-K(+)-ATPases. Evaluation of enzymatic functions along the nephron and collecting duct and studies in HKalpha(1) and HKalpha(2) knockout mice suggest that the H(+)-K(+)-ATPases may function to transport ions other than protons and potassium. These reports and recent studies in mice lacking both HKalpha(1) and HKalpha(2) suggest important roles for the renal H(+)-K(+)-ATPases in acid/base balance as well as potassium and sodium homeostasis. Molecular modeling studies based on the crystal structure of a related enzyme have made it possible to evaluate the structures of HKalpha(1) and HKalpha(2) and provide a means to study the specific cation transport properties of H(+)-K(+)-ATPases. Studies to characterize the cation specificity of these enzymes under different physiological conditions are necessary to fully understand the role of the H(+)-K(+) ATPases in renal physiology.
Collapse
Affiliation(s)
- Michelle L Gumz
- Research Service, North Florida/South Georgia Veterans Health System, Gainesville, Florida, USA
| | | | | | | | | |
Collapse
|
12
|
Zies DL, Gumz ML, Wingo CS, Cain BD. The renal H+, K+-ATPases as therapeutic targets. Expert Opin Ther Targets 2007; 11:881-90. [PMID: 17614757 DOI: 10.1517/14728222.11.7.881] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The kidney is an important regulatory organ responsible for maintaining constant blood volume and composition despite wide variations in the intake of food and water. Throughout the nephron, the functional unit of the kidney, there is a wide variety of proteins that function to add additional waste products and to recover needed materials from the lumen filtrate. The collecting duct of the nephron is the primary renal location for the H+, K+-ATPases, a group of ion pumps that function in both acid/base balance and potassium homeostasis. This review summarizes the present understanding of the structure and functions for the different subtypes of the H+, K+-ATPases under specific physiologic conditions. The obstacles in determining the pharmacologic properties of the different subtypes are considered and future directions for the inhibition and/or stimulation of the H+, K+-ATPases are evaluated.
Collapse
Affiliation(s)
- Deborah L Zies
- University of Mary Washington, Department of Biology, Fredericksburg, VA 22401, USA
| | | | | | | |
Collapse
|
13
|
Guennoun-Lehmann S, Fonseca JE, Horisberger JD, Rakowski RF. Palytoxin acts on Na(+),K (+)-ATPase but not nongastric H(+),K (+)-ATPase. J Membr Biol 2007; 216:107-16. [PMID: 17639367 PMCID: PMC2396460 DOI: 10.1007/s00232-007-9040-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Accepted: 05/14/2007] [Indexed: 10/23/2022]
Abstract
Palytoxin (PTX) opens a pathway for ions to pass through Na,K-ATPase. We investigate here whether PTX also acts on nongastric H,K-ATPases. The following combinations of cRNA were expressed in Xenopus laevis oocytes: Bufo marinus bladder H,K-ATPase alpha(2)- and Na,K-ATPase beta(2)-subunits; Bufo Na,K-ATPase alpha(1)- and Na,K-ATPase beta(2)-subunits; and Bufo Na,K-ATPase beta(2)-subunit alone. The response to PTX was measured after blocking endogenous Xenopus Na,K-ATPase with 10 microM ouabain. Functional expression was confirmed by measuring (86)Rb uptake. PTX (5 nM: ) produced a large increase of membrane conductance in oocytes expressing Bufo Na,K-ATPase, but no significant increase occurred in oocytes expressing Bufo H,K-ATPase or in those injected with Bufo beta(2)-subunit alone. Expression of the following combinations of cDNA was investigated in HeLa cells: rat colonic H,K-ATPase alpha(1)-subunit and Na,K-ATPase beta(1)-subunit; rat Na,K-ATPase alpha(2)-subunit and Na,K-ATPase beta(2)-subunit; and rat Na,K-ATPase beta(1)- or Na,K-ATPase beta(2)-subunit alone. Measurement of increases in (86)Rb uptake confirmed that both rat Na,K and H,K pumps were functional in HeLa cells expressing rat colonic HKalpha(1)/NKbeta(1) and NKalpha(2)/NKbeta(2). Whole-cell patch-clamp measurements in HeLa cells expressing rat colonic HKalpha(1)/NKbeta(1) exposed to 100 nM PTX showed no significant increase of membrane current, and there was no membrane conductance increase in HeLa cells transfected with rat NKbeta(1)- or rat NKbeta(2)-subunit alone. However, in HeLa cells expressing rat NKalpha(2)/NKbeta(2), outward current was observed after pump activation by 20 mM K(+) and a large membrane conductance increase occurred after 100 nM PTX. We conclude that nongastric H,K-ATPases are not sensitive to PTX when expressed in these cells, whereas PTX does act on Na,K-ATPase.
Collapse
Affiliation(s)
| | - James E. Fonseca
- School of Electrical Engineering & Computer Science, Ohio University, Athens, OH 45701 USA
| | - Jean-Daniel Horisberger
- Dept. of Pharmacology and Toxicology of the University of Lausanne, Rue du Bugnon 27, CH-1005 Lausanne, Switzerland
| | - Robert F. Rakowski
- Department of Biological Sciences, Ohio University, Athens, OH 45701 USA
| |
Collapse
|
14
|
Abstract
Two H(+), K(+)-adenosine triphosphatase (ATPase) proteins participate in K(+) absorption and H(+) secretion in the renal medulla. Both the gastric (HKalpha(1)) and colonic (HKalpha(2)) H(+),K(+)-ATPases have been localized and characterized by a number of techniques, and are known to be highly regulated in response to acid-base and electrolyte disturbances. Both ATPases are dimers of composition alpha/beta that localize to the apical membrane and both interact with the tetraspanin protein CD63. Although CD63 interacts with the carboxy-terminus of the alpha-subunit of the colonic H(+),K(+)-ATPase, it interacts with the beta-subunit of the gastric H(+),K(+)-ATPase. Pharmacologically, both ATPases are distinct; for example, the gastric H(+),K(+)-ATPase is inhibited by Sch-28080, but the colonic H(+),K(+)-ATPase is inhibited by ouabain (a classic inhibitor of the Na(+)-pump) and is completely insensitive to Sch-28080. The alpha-subunit of the colonic H(+),K(+)-ATPase is the only subunit of the X(+),K(+)-ATPase superfamily that has 3 different splice variants that emerge by deletion or elongation of the amino-terminus. The messenger RNA and protein of one of these splice variants (HKalpha(2C)) is specifically up-regulated in newborn rats and becomes undetectable in adult rats. Therefore, HKalpha(2), in addition to its role in potassium and acid-base homeostasis, appears to play a significant role in early growth and development. Finally, because chronic hypokalemia appears to be the most potent stimulus for upregulation of HKalpha(2), we propose that the HKalpha(2) participates importantly in the maintenance of chronic metabolic alkalosis.
Collapse
Affiliation(s)
- Juan Codina
- Section on Nephrology, Department of Internal Medicine, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA
| | | |
Collapse
|
15
|
Swarts HGP, Koenderink JB, Willems PHGM, De Pont JJHHM. The human non-gastric H,K-ATPase has a different cation specificity than the rat enzyme. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1768:580-9. [PMID: 17137554 DOI: 10.1016/j.bbamem.2006.10.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Revised: 10/02/2006] [Accepted: 10/19/2006] [Indexed: 11/24/2022]
Abstract
The primary sequence of non-gastric H,K-ATPase differs much more between species than that of Na,K-ATPase or gastric H,K-ATPase. To investigate whether this causes species-dependent differences in enzymatic properties, we co-expressed the catalytic subunit of human non-gastric H,K-ATPase in Sf9 cells with the beta(1) subunit of rat Na,K-ATPase and compared its properties with those of the rat enzyme (Swarts et al., J. Biol. Chem. 280, 33115-33122, 2005). Maximal ATPase activity was obtained with NH(4)(+) as activating cation. The enzyme was also stimulated by Na(+), but in contrast to the rat enzyme, hardly by K(+). SCH 28080 inhibited the NH(4)(+)-stimulated activity of the human enzyme much more potently than that of the rat enzyme. The steady-state phosphorylation level of the human enzyme decreased with increasing pH, [K(+)], and [Na(+)] and nearly doubled in the presence of oligomycin. Oligomycin increased the sensitivity of the phosphorylated intermediate to ADP, demonstrating that it inhibited the conversion of E(1)P to E(2)P. All three cations stimulated the dephosphorylation rate dose-dependently. Our studies support a role of the human enzyme in H(+)/Na(+) and/or H(+)/NH(4)(+) transport but not in Na(+)/K(+) transport.
Collapse
Affiliation(s)
- Herman G P Swarts
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | | | | | | |
Collapse
|
16
|
Lerner M, Lemke D, Bertram H, Schillers H, Oberleithner H, Caplan MJ, Reinhardt J. An extracellular loop of the human non-gastric H,K-ATPase alpha-subunit is involved in apical plasma membrane polarization. Cell Physiol Biochem 2006; 18:75-84. [PMID: 16914892 DOI: 10.1159/000095169] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The human non-gastric H,K-ATPase, ATP1AL1, belongs to the gene family of P-type ATPases. Consistent with their physiological roles in ion transport, members of this group, including the Na,KATPase and the gastric and non-gastric H,K-ATPases, are differentially polarized to either the basolateral or apical plasma membrane in epithelial cells. However, their polarized distribution is highly complex and depends on specific sorting signals or motifs which are recognized by the subcellular targeting machinery. For the gastric H,K-ATPase it has been suggested that the 4(th) transmembrane spanning domain (TM4) and its flanking regions induce conformational sorting motifs which direct the ion pump exclusively to the epithelial apical membrane. Here, we show in transfected Madin-Darby canine kidney (MDCK) cells that the related non-gastric H,KATPase, ATP1AL1, does contain similar sorting motifs in close proximity to TM4. A short extracellular loop between TM3 and TM4 is critical for this pump's apical delivery. A single point mutation in the corresponding region redirects ATP1AL1 to the basolateral membrane. In conclusion, our work provides further evidence that the cellular distribution of P-type ATPases is determined by conformational sorting motifs.
Collapse
|
17
|
Shibata T, Hibino H, Doi K, Suzuki T, Hisa Y, Kurachi Y. Gastric type H+,K+-ATPase in the cochlear lateral wall is critically involved in formation of the endocochlear potential. Am J Physiol Cell Physiol 2006; 291:C1038-48. [PMID: 16822945 DOI: 10.1152/ajpcell.00266.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cochlear endolymph has a highly positive potential of approximately +80 mV known as the endocochlear potential (EP). The EP is essential for hearing and is maintained by K(+) circulation from perilymph to endolymph through the cochlear lateral wall. Various K(+) transport apparatuses such as the Na(+),K(+)-ATPase, the Na(+)-K(+)-2Cl(-) cotransporter, and the K(+) channels Kir4.1 and KCNQ1/KCNE1 are expressed in the lateral wall and are known to play indispensable roles in cochlear K(+) circulation. The gastric type of the H(+),K(+)-ATPase was also shown to be expressed in the cochlear lateral wall (Lecain E, Robert JC, Thomas A, and Tran Ba Huy P. Hear Res 149: 147-154, 2000), but its functional role has not been well studied. In this study we examined the precise localization of H(+),K(+)-ATPase in the cochlea and its involvement in formation of EP. RT-PCR analysis showed that the cochlea expressed mRNAs of gastric alpha(1)-, but not colonic alpha(2)-, and beta-subunits of H(+),K(+)-ATPase. Immunolabeling of an antibody specific to the alpha(1) subunit was detected in type II, IV, and V fibrocytes distributed in the spiral ligament of the lateral wall and in the spiral limbus. Strong immunoreactivity was also found in the stria vascularis. Immunoelectron microscopic examination exhibited that the H(+),K(+)-ATPase was localized exclusively at the basolateral site of strial marginal cells. Application of Sch-28080, a specific inhibitor of gastric H(+),K(+)-ATPase, to the spiral ligament as well as to the stria vascularis caused prominent reduction of EP. These results may imply that the H(+),K(+)-ATPase in the cochlear lateral wall is crucial for K(+) circulation and thus plays a critical role in generation of EP.
Collapse
Affiliation(s)
- Toshiaki Shibata
- Div. of Molecular and Cellular Pharmacology, Department of Pharmacology, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan
| | | | | | | | | | | |
Collapse
|
18
|
Codina J, Liu J, Bleyer AJ, Penn RB, DuBose TD. Phosphorylation of S955 at the protein kinase A consensus promotes maturation of the alpha subunit of the colonic H+,K+ -ATPase. J Am Soc Nephrol 2006; 17:1833-40. [PMID: 16738016 DOI: 10.1681/asn.2006010032] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
All the alpha subunits of the Na+,K+ -ATPases and H+,K+ -ATPases have a protein kinase A (PKA) consensus sequence near or in the ninth transmembrane domain. The role of this domain in influencing alpha subunit synthesis/degradation, plasma membrane localization, and 86Rb+ uptake has not been established for the alpha subunit of the colonic H+,K+ -ATPase. This study examined the effect of mutating S955 (within the PKA consensus site of the alpha subunit of the colonic H+,K+ -ATPase [HKalpha2]) to alanine (S955/A) or aspartic acid (S955/D) on alpha subunit expression and function. The results demonstrate that a negatively charged amino acid at position 955 of HKalpha2 promotes higher expression levels of both whole-cell and plasma membrane-localized HKalpha2. Moreover, inhibition of PKA reduced expression of wild-type HKalpha2 and associated 86Rb+ uptake. Last, the activity of the HKalpha2 S955/A was rescued by treatment with 4-phenylbutyric acid, a compound that was shown previously to restore function to the cystic fibrosis transmembrane conductance regulator.
Collapse
Affiliation(s)
- Juan Codina
- Sections on Nephrology and Molecular Medicine, Department of Internal Medicine, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157, USA
| | | | | | | | | |
Collapse
|
19
|
Qiu LY, Swarts HGP, Tonk ECM, Willems PHGM, Koenderink JB, De Pont JJHHM. Conversion of the Low Affinity Ouabain-binding Site of Non-gastric H,K-ATPase into a High Affinity Binding Site by Substitution of Only Five Amino Acids. J Biol Chem 2006; 281:13533-13539. [PMID: 16531406 DOI: 10.1074/jbc.m600551200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P-type ATPases of the IIC subfamily exhibit large differences in sensitivity toward ouabain. This allows a strategy in which ouabain-insensitive members of this subfamily are used as template for mutational elucidation of the ouabain-binding site. With this strategy, we recently identified seven amino acids in Na,K-ATPase that conferred high affinity ouabain binding to gastric H,K-ATPase (Qiu, L. Y., Krieger, E., Schaftenaar, G., Swarts, H. G. P., Willems, P. H. G. M., De Pont, J. J. H. H. M., and Koenderink, J. B. (2005) J. Biol. Chem. 280, 32349-32355). Because important, but identical, amino acids were not recognized in that study, here we used the non-gastric H,K-ATPase, which is rather ouabain-insensitive, as template. The catalytic subunit of this enzyme, in which several amino acids from Na,K-ATPase were incorporated, was expressed with the Na,K-ATPase beta1 subunit in Xenopus laevis oocytes. A chimera containing 14 amino acids, located in M4, M5, and M6, which are unique to Na,K-ATPase, displayed high affinity ouabain binding. Four of these residues, all located in M5, appeared dispensable for high affinity binding. Individual mutation of the remaining 10 residues to their non-gastric H,K-ATPase counterparts yielded five amino acids (Glu312,Gly319, Pro778, Leu795, and Cys802) whose mutation resulted in a loss of ouabain binding. In a final gain-of-function experiment, we introduced these five amino acids in different combinations in non-gastric H,K-ATPase and demonstrated that all five were essential for high affinity ouabain binding. The non-gastric H,K-ATPase with these five mutations had a similar apparent affinity for ouabain as the wild type Na,K-ATPase and showed a 2000 times increased affinity for ouabain in the NH4+-stimulated ATPase activity in membranes of transfected Sf9 cells.
Collapse
Affiliation(s)
- Li Yan Qiu
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Herman G P Swarts
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Elisa C M Tonk
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Peter H G M Willems
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Jan B Koenderink
- Department of Pharmacology/Toxicology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Jan Joep H H M De Pont
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands.
| |
Collapse
|
20
|
Pestov NB, Korneenko TV, Shakhparonov MI, Shull GE, Modyanov NN. Loss of acidification of anterior prostate fluids in Atp12a-null mutant mice indicates that nongastric H-K-ATPase functions as proton pump in vivo. Am J Physiol Cell Physiol 2006; 291:C366-74. [PMID: 16525125 DOI: 10.1152/ajpcell.00042.2006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The physiological functions of nongastric (colonic) H-K-ATPase (gene symbol Atp12a), unlike those of Na-K-ATPase and gastric H-K-ATPase, are poorly understood. It has been suggested that it pumps Na+ more efficiently than H+; however, so far, there is no direct evidence that it pumps H+ in vivo. Previously, we found that the nongastric H-K-ATPase alpha-subunit is expressed in apical membranes of rodent anterior prostate epithelium, in a complex with the Na-K-ATPase beta1-subunit. Here we report the effects of Atp12a gene ablation on polarization of the beta1-subunit and secretory function of the anterior prostate. In nongastric H-K-ATPase-deficient prostate, the Na-K-ATPase alpha-subunit resided exclusively in basolateral membranes; however, the beta1-subunit disappeared from apical membranes, demonstrating that beta1 is an authentic subunit of nongastric H-K-ATPase in vivo and that apical localization of beta1 in the prostate is completely dependent on its association with the nongastric H-K-ATPase alpha-subunit. A remarkable reduction in acidification of anterior prostate fluids was observed: pH 6.38 +/- 0.14 for wild-type mice and 6.96 +/- 0.10 for homozygous mutants. These results show that nongastric H-K-ATPase is required for acidification of luminal prostate fluids, thereby providing a strong in vivo correlate of previous functional expression studies demonstrating that it operates as a proton pump.
Collapse
Affiliation(s)
- Nikolay B Pestov
- Dept. of Physiology, Pharmacology, Metabolism, and Cardiovascular Sciences, Med. Univ. of Ohio, 3035 Arlington Ave., Toledo, OH 43614, USA
| | | | | | | | | |
Collapse
|
21
|
Abstract
There is a positive association between diets rich in potassium, control of blood pressure, and prevention of stroke. Extracellular [K+] is regulated closely to maintain normal membrane excitability by the concerted regulatory responses of muscle and kidney. Although kidney is responsible for ultimately matching K+ output to K+ intake each day, muscle contains more than 90% of the body's K+ and can buffer changes in extracellular fluid [K+] by either acutely taking up extracellular fluid K+ or releasing intracellular fluid K+ from muscle. It long has been assumed that the changes in muscle K+ transport are a function of sodium pump (Na,K-adenosine triphosphatase [Na, K-ATPasel]) abundance, especially that of the alpha2 isoform, which predominates in skeletal muscle. To test the physiologic significance of changes in muscle Na,K-ATPase expression, we developed the K+ clamp, which measures insulin-stimulated cellular K+ uptake in vivo in the conscious rat. By using the K+ clamp we discovered that significant insulin resistance to cell K+ uptake occurs as follows: (1) early in K+ deprivation before a decrease in muscle sodium pump pool size, and (2) during glucocorticoid treatment, which increases muscle Na,K-ATPase alpha2 levels greater than 50%. We also discovered that adaptation of renal and extrarenal K+ handling to altered K+ balance often occurs without changes in plasma [K+], supporting a feedforward mechanism involving K+ sensing in the splanchnic bed and adjustment of K+ handling. These findings establish the advantage of combining molecular analyses of Na,K-ATPase expression and activity with systems analyses of cellular K+ uptake and excretion in vivo to reveal regulatory mechanisms operating to control K+ homeostasis.
Collapse
Affiliation(s)
- Alicia A McDonough
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, CA 90089-9142, USA
| | | |
Collapse
|
22
|
Dherbecourt O, Cheval L, Bloch-Faure M, Meneton P, Doucet A. Molecular identification of Sch28080-sensitive K-ATPase activities in the mouse kidney. Pflugers Arch 2005; 451:769-75. [PMID: 16208521 DOI: 10.1007/s00424-005-1508-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 07/07/2005] [Accepted: 08/17/2005] [Indexed: 10/25/2022]
Abstract
Rat collecting ducts display either an ouabain-insensitive or an ouabain-sensitive K-ATPase activity inhibited by Sch28080 according as animals are fed a normal or a potassium-depleted diet (types I and III K-ATPase, respectively). Two isoforms of H,K-ATPase have been cloned from rat gastric mucosa and colon, respectively. Gastric and colonic H,K-ATPase are expressed in the kidney, suggesting that they might account for types I and III K-ATPases. However, this hypothesis is not fully supported by segmental expression of gastric and colonic H,K-ATPase along the rat collecting duct, as well as by comparison of the pharmacological properties of gastric and colonic H,K-ATPase expressed in Xenopus ovocyte and types I and III K-ATPases in rat collecting ducts. The aim of the present work is to address directly the molecular origin of types I and III K-ATPases in the mouse collecting duct by measuring K-ATPase activities in collecting ducts of wild-type mice and mice genetically deficient in either gastric or colonic H,K-ATPase fed either a regular or a potassium-depleted diet. Like the rat, mouse collecting ducts display type I or III K-ATPase activity when fed a regular or a potassium-depleted diet, respectively. Type I K-ATPase activity is detected in colonic H,K-ATPase-deficient mice but not in gastric H,K-ATPase-deficient animals. Conversely, type III K-ATPase activity disappears in colonic H,K-ATPase-deficient but not in gastric H,K-ATPase-deficient mice. In conclusion, types I and III K-ATPases measured in collecting ducts of normal and potassium-depleted mice reflect the functional expression of gastric and colonic H,K-ATPase, respectively.
Collapse
Affiliation(s)
- Olivier Dherbecourt
- Laboratoire de Physiologie et Génomique Rénales, Unité Mixte de Recherche CNRS/UPMC 7134, IFR 58, Institut des Cordeliers, 15 Rue de l'Ecole de Médecine, 75270 Paris Cedex 6, France
| | | | | | | | | |
Collapse
|
23
|
Yenisehirli A, Onur R. Positive inotropic and negative chronotropic effects of proton pump inhibitors in isolated rat atrium. Eur J Pharmacol 2005; 519:259-66. [PMID: 16125697 DOI: 10.1016/j.ejphar.2005.06.040] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 03/22/2005] [Accepted: 06/20/2005] [Indexed: 11/19/2022]
Abstract
The effects of three specific H+/K+-ATPase inhibitors (omeprazole, lansoprazole and SCH 28080 (2-methyl-8-(phenylmethoxy)-imidazo[1,2-a] pyridine-3-acetonitrile)) were investigated on the mechanical and electrophysiological properties of rat atrium, in vitro. Omeprazole (100-300 microM), lansoprazole (100-300 microM) and SCH 28080 (10-100 microM) increased the amplitude of contractions and decreased the beating rate. These effects are reversible, reproducible and correlated with their order of potency as gastric H+/K+-ATPase inhibitors; SCH 28080 > omeprazole = lansoprazole. Cardiac effects of proton pump inhibitors were not inhibited with phentolamine (5 microM), propranolol (15 microM), atropine (1 microM), ouabain (2 microM), theophylline (300 microM) and milrinone (100 microM). Ouabain-induced increase in beating rate and contracture development were antagonized by H+/K+-ATPase inhibitors. Ouabain increased the positive inotropic effect of H+/K+-ATPase inhibitors. Lansoprazole (300 microM) significantly prolonged the duration of action potentials in rat atrial cells. H+/K+-ATPase may play a crucial role in the mechanical and electrophysiological properties of rat atrial myocardium.
Collapse
Affiliation(s)
- Aydan Yenisehirli
- Department of Pharmacology, Faculty of Medicine, Gaziosmanpasa University, Tokat 60100, Turkey.
| | | |
Collapse
|
24
|
Mayol JM, Alarma-Estrany P, Adame-Navarrete Y, Roldan EM, Toral FH, Fernandez-Represa JA. Effects of luminal ATPase inhibitors on electrogenic ion transport in rat distal colon. J Surg Res 2005; 129:85-9. [PMID: 16112134 DOI: 10.1016/j.jss.2005.05.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2004] [Revised: 04/06/2005] [Accepted: 05/31/2005] [Indexed: 01/28/2023]
Abstract
BACKGROUND The involvement of transport proteins, other than chloride channels, expressed in the luminal membrane of epithelial cells in regulated chloride secretion in native colon remains poorly understood. There are at least two distinct ATPases expressed in the apical membrane of rat colonocytes. They can be distinguished by their different sensitivity to the vanadium-derived compound orthovanadate. The objective was to study the effects of luminal ATPase inhibitors on regulated chloride secretion using elecrophysiological and pharmacological approaches. MATERIALS AND METHODS Unstripped rat distal colon segments were mounted in Ussing chambers. Potential difference, transepithelial resistance, and short-circuit current across unstripped colon segments were monitored with a dual voltage/current clamp. RESULTS Luminal application of VO4(3-) did not alter baseline electrical values in rat distal colon but dose-dependently inhibited forskolin-stimulated Isc. Luminal ouabain (1 mm) did not blunt the response to the cAMP agonist. The inhibitory effect of luminal VO4(3-) occurred at a site distal to cAMP generation and was rather specific for the cyclic nucleotide-dependent signaling pathway, because the response to the Ca2+ agonist carbachol was largely preserved. CONCLUSION VO4(3-) inhibits cAMP-stimulated Cl- secretion in rat distal colon at a site distal to cAMP generation without altering intestinal permeability. Ouabain-sensitive luminal K+-ATPases do not seem to contribute to forskolin-stimulated electrogenic ion transport. These findings may suggest new therapeutic targets for secretory diarrhea.
Collapse
Affiliation(s)
- Julio M Mayol
- Servicio de Cirugia I, Hospital Clinico San Carlos, Madrid, Spain.
| | | | | | | | | | | |
Collapse
|
25
|
Swarts HGP, Koenderink JB, Willems PHGM, De Pont JJHHM. The non-gastric H,K-ATPase is oligomycin-sensitive and can function as an H+,NH4(+)-ATPase. J Biol Chem 2005; 280:33115-22. [PMID: 16046397 DOI: 10.1074/jbc.m504535200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We used the baculovirus/Sf9 expression system to gain new information on the mechanistic properties of the rat non-gastric H,K-ATPase, an enzyme that is implicated in potassium homeostasis. The alpha2-subunit of this enzyme (HKalpha2) required a beta-subunit for ATPase activity thereby showing a clear preference for NaKbeta1 over NaKbeta3 and gastric HKbeta. NH4(+), K+, and Na+ maximally increased the activity of HKalpha2-NaKbeta1 to 24.0, 14.2, and 5.0 micromol P(i) x mg(-1) protein x h(-1), respectively. The enzyme was inhibited by relatively high concentrations of ouabain and SCH 28080, whereas it was potently inhibited by oligomycin. From the phosphorylation level in the presence of oligomycin and the maximal NH4(+)-stimulated ATPase activity, a turnover number of 20,000 min(-1) was determined. All three cations decreased the steady-state phosphorylation level and enhanced the dephosphorylation rate, disfavoring the hypothesis that Na+ can replace H+ as the activating cation. The potency with which vanadate inhibited the cation-activated enzyme decreased in the order K+ > NH4(+) > Na+, indicating that K+ is a stronger E2 promoter than NH4(+), whereas in the presence of Na+ the enzyme is in the E1 form. For K+ and NH4(+), the E2 to E1 conformational equilibrium correlated with their efficacy in the ATPase reaction, indicating that here the transition from E2 to E1 is rate-limiting. Conversely, the low maximal ATPase activity with Na+ is explained by a poor stimulatory effect on the dephosphorylation rate. These data show that NH4(+) can replace K+ with similar affinity but higher efficacy as an extracellular activating cation in rat nongastric H,K-ATPase.
Collapse
Affiliation(s)
- Herman G P Swarts
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands
| | | | | | | |
Collapse
|
26
|
Abstract
BACKGROUND The present experiments were designed to study the importance of the carboxy-terminus of HKalpha2, for both function and integrity of assembly with beta1-Na+,K+-ATPase. METHODS For this purpose, stop codons were created, by polymerase chain reaction (PCR), at different positions in the carboxy-terminus of HKalpha2. Subsequently, chimeras between HKalpha2 and the carboxy-terminus of alpha1-Na+,K+-ATPase or with the carboxy-terminus of the gastric H+,K+-ATPase were created. Human embryonic kidney HEK-293 cells were used as expression systems for functional studies using 86Rb+ uptake and alpha/beta assembly using specific antibodies. RESULTS The results demonstrate that the entire carboxy-terminus of HKalpha2 is required for optimal protection of the alpha/beta complex from degradation and for functionality as evidenced by 86Rb+ uptake. The results also demonstrate that there was flexibility in the sequence of the carboxy-terminus. The last two tyrosines (Y1035Y1036) of HKalpha2 could be mutated to alanines and the carboxy-terminus of HKalpha2 could be replaced by the carboxy-terminus of alpha1-Na+,K+-ATPase while preserving transport activity. CONCLUSION The entire carboxy-terminus of HKalpha2 is required for stable assembly with beta1-Na+,K+-ATPase and functionality.
Collapse
Affiliation(s)
- Juan Codina
- Sections of Nephrology and Molecular Medicine, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
| | | | | |
Collapse
|
27
|
Codina J, Li J, DuBose TD. CD63 interacts with the carboxy terminus of the colonic H+-K+-ATPase to decrease [corrected] plasma membrane localization and 86Rb+ uptake. Am J Physiol Cell Physiol 2005; 288:C1279-86. [PMID: 15647390 PMCID: PMC1868892 DOI: 10.1152/ajpcell.00463.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The carboxy terminus (CT) of the colonic H(+)-K(+)-ATPase is required for stable assembly with the beta-subunit, translocation to the plasma membrane, and efficient function of the transporter. To identify protein-protein interactions involved in the localization and function of HKalpha(2), we selected 84 amino acids in the CT of the alpha-subunit of mouse colonic H(+)-K(+)-ATPase (CT-HKalpha(2)) as the bait in a yeast two-hybrid screen of a mouse kidney cDNA library. The longest identified clone was CD63. To characterize the interaction of CT-HKalpha(2) with CD63, recombinant CT-HKalpha(2) and CD63 were synthesized in vitro and incubated, and complexes were immunoprecipitated. CT-HKalpha(2) protein (but not CT-HKalpha(1)) coprecipitated with CD63, confirming stable assembly of HKalpha(2) with CD63. In HEK-293 transfected with HKalpha(2) plus beta(1)-Na(+)-K(+)-ATPase, suppression of CD63 by RNA interference increased cell surface expression of HKalpha(2)/NKbeta(1) and (86)Rb(+) uptake. These studies demonstrate that CD63 participates in the regulation of the abundance of the HKalpha(2)-NKbeta(1) complex in the cell membrane.
Collapse
Affiliation(s)
| | | | - Thomas D. DuBose
- Corresponding author: Thomas D. DuBose, Jr., M.D., Department of Internal Medicine, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, Tel. (336)-716-2715, Fax. (336)-716-2273, e-mail:
| |
Collapse
|
28
|
Johansson M, Jansson T, Pestov NB, Powell TL. Non-gastric H+/K+ ATPase is present in the microvillous membrane of the human placental syncytiotrophoblast. Placenta 2004; 25:505-11. [PMID: 15135233 DOI: 10.1016/j.placenta.2003.11.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2003] [Revised: 11/18/2003] [Accepted: 11/19/2003] [Indexed: 11/25/2022]
Abstract
In humans, the non-gastric H(+)/K(+)ATPase (ATP1AL1) has previously been shown to be expressed in the epithelia of skin, kidney and colon. In this study we tested the hypothesis that the non-gastric H(+)/K(+)ATPase is localized to the syncytiotrophoblast, the transporting epithelium of the human placenta. Microvillous (MVM) and basal plasma membranes (BM) of the syncytiotrophoblast were isolated from term placenta and membrane proteins were separated using SDS-PAGE. The ATP1AL1 protein was identified as a 114 kD band in both MVM and BM by Western blot, however, the protein was more abundant in the MVM. Using immunocytochemistry H(+)/K(+)ATPase protein was localized in MVM but not BM. We constructed primers specific for ATP1AL1 and performed RT-PCR on RNA isolated from human placenta and human kidney. A product of the expected size could be detected in both tissues after 30 cycles of amplification. The sequence identity of this 517 nucleotide product was confirmed by sequencing and found to be identical to the human non-gastric H(+)/K(+)ATPase. The activity of this proton pump appears to be low in normal healthy placental at term, however, it is speculated that MVM non-gastric H(+)/K(+)ATPase may be important in pathological states. In conclusion, non-gastric H(+)/K(+)ATPase is present in the microvillous plasma membrane of the transporting epithelia of the human placenta.
Collapse
Affiliation(s)
- M Johansson
- Perinatal Center, Department of Physiology and Pharmacology, Göteborg University, Box 432, 40530 Goteborg, Sweden
| | | | | | | |
Collapse
|
29
|
Li J, Codina J, Petroske E, Werle MJ, Willingham MC, DuBose TD. The effect of beta-subunit assembly on function and localization of the colonic H+,K+-ATPase alpha-subunit. Kidney Int 2004; 66:1068-75. [PMID: 15327400 DOI: 10.1111/j.1523-1755.2004.00856.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Previous experiments from our laboratory have demonstrated that HKalpha(2) coimmunoprecipitated with beta(1)-Na(+),K(+)-ATPase. Although HKalpha(2) is expressed abundantly in the apical membrane of distal colon, the demonstration that beta(1) localizes to this same membrane in distal colon has not been demonstrated previously. METHODS Immunolocalization was performed in distal colon using a polyclonal antibody against HKalpha(2) and a monoclonal antibody against beta(1). RESULTS The results demonstrate that HKalpha(2) localizes to the apical membrane. Two pools of beta(1)-Na(+),K(+)-ATPase were detected. The first localized to the apical membrane. The second pool was detected in the basolateral membrane when distal colon sections were deglycosylated with glycosidase F. Therefore, our results demonstrate that beta(1) localizes to the apical membrane with HKalpha(2), and supports the view that beta(1) is the physiologic beta-subunit for HKalpha(2). We tested, therefore, the efficiency of the two beta-subunits expressed in distal colon (beta(1) and beta(3)) to support the activity of HKalpha(2). Human embryonic kidney HEK-293 cells were transiently cotransfected with HKalpha(2) plus beta(1) or HKalpha(2) plus beta(3). Subsequently, (86)Rb(+)-uptake and plasma membrane localization were evaluated. The results demonstrate that both HKalpha(2)/beta(1) and HKalpha(2)/beta(3) support (86)Rb(+)-uptake. However, (86)Rb(+)-uptake measured in the cells cotransfected with HKalpha(2) plus beta(1) exceeded that measured in cells expressing HKalpha(2)/beta(3). Fluorescence microscopy using enhanced green fluorescent protein cloned at the amino-terminus of HKalpha(2) demonstrated protein migration to the plasma membrane in cells cotransfected with EGFP-HKalpha(2) plus beta(1). In contrast, in cells cotransfected with EGFP-HKalpha(2) plus beta(3), the vast majority of the protein remained confined to intracellular compartments. The significantly higher (86)Rb(+)-uptake corresponded to additional localization of HKalpha(2) to the plasma membrane when coexpressed with beta(1) compared to beta(3). CONCLUSION Taken together, these and previous results from our laboratory indicate that beta(1)-Na(+),K(+)-ATPase is likely to represent the most physiologic and efficient subunit for HKalpha(2) assembly in distal colon.
Collapse
Affiliation(s)
- Jian Li
- Department of Internal Medicine, Wake Forest University Medical School, Winston-Salem, North Carolina 27157, USA
| | | | | | | | | | | |
Collapse
|
30
|
Pestov NB, Korneenko TV, Radkov R, Zhao H, Shakhparonov MI, Modyanov NN. Identification of the β-subunit for nongastric H-K-ATPase in rat anterior prostate. Am J Physiol Cell Physiol 2004; 286:C1229-37. [PMID: 14749213 DOI: 10.1152/ajpcell.00393.2003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The structural organization of nongastric H-K-ATPase, unlike that of closely related Na-K-ATPase and gastric H-K-ATPase, is not well characterized. Recently, we demonstrated that nongastric H-K-ATPase α-subunit (αng) is expressed in apical membranes of rodent prostate. Its highest level, as well as relative abundance, with respect to α1-isoform of Na-K-ATPase, was observed in anterior lobe. Here, we aimed to determine the subunit composition of nongastric H-K-ATPase through the detailed analysis of the expression of all known X-K-ATPase β-subunits in rat anterior prostate (AP). RT-PCR detects transcripts of β-subunits of Na-K-ATPase only. Measurement of absolute protein content of these three β-subunit isoforms, with the use of quantitative Western blotting of AP membrane proteins, indicates that the abundance order is β1> β3≫ β2. Immunohistochemical experiments demonstrate that β1is present predominantly in apical membranes, coinciding with αng, whereas β3is localized in the basolateral compartment, coinciding with α1. This is the first direct demonstration of the αng-β1colocalization in situ indicating that, in rat AP, αngassociates only with β1. The existence of αng-β1complex has been confirmed by immunoprecipitation experiments. These results indicate that β1-isoform functions as the authentic subunit of Na-K-ATPase and nongastric H-K-ATPase. Putatively, the intracellular polarization of X-K-ATPase isoforms depends on interaction with other proteins.
Collapse
Affiliation(s)
- Nikolay B Pestov
- Department of Pharmacology, Medical College of Ohio, Toledo, 43614, USA
| | | | | | | | | | | |
Collapse
|
31
|
Li J, Codina J, Petroske E, Werle MJ, DuBose TD. The carboxy terminus of the colonic H+,K+-ATPase α-subunit is required for stable β subunit assembly and function. Kidney Int 2004; 65:1301-10. [PMID: 15086469 DOI: 10.1111/j.1523-1755.2004.00507.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND The present experiments were designed to study the importance of the carboxy-terminus of colonic H(+), K(+)-ATPase alpha-subunit (HKalpha(2)), for both function as well as integrity of assembly with beta1-Na(+), K(+)-ATPase. METHODS For this purpose, a mutation of 84 amino acids in the carboxy-terminus was created (DeltaHKalpha(2)) and HEK-293 cells were used as expression systems for functional studies using (86)Rb(+)-uptake, coimmunoprecipitation using specific antibodies and fluorescence microscopy using green fluorescent protein. RESULTS The results demonstrate that comparable levels of expression of HKalpha(2) and DeltaHKalpha(2) mRNA were observed when cells were cotransfected with beta1 subunit. However, the abundance of expression of full length HKalpha(2) protein exceeded that of the truncated protein DeltaHKalpha(2). Ouabain-sensitive (86)Rb(+)-uptake was present only in cells cotransfected with HKalpha(2)/beta(1), indicating that the mutation was incapable of sustaining functionality. Coimmunoprecipitation experiments demonstrated that HKalpha(2) protein was immunoprecipitated more abundantly than DeltaHKalpha(2) when coexpressed with beta1. The use of sucrose gradients and green fluorescence protein immunofluorescence demonstrated that while the DeltaHKalpha(2)/beta(1) complex was confined to the endoplasmic reticulum, the HKalpha(2)/beta(1) complex translocated to the plasma membrane. CONCLUSION Taken together, our results are consistent with the view that the carboxy-terminus of HKalpha(2) facilitates the proper folding of the HKalpha(2)/beta(1) complex allowing translocation of the heterodimer to the plasma membrane where potassium uptake occurs. Otherwise, the alpha/beta complex is destined for degradation.
Collapse
Affiliation(s)
- Jian Li
- Department of Internal Medicine, Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
| | | | | | | | | |
Collapse
|
32
|
Reinhardt J, Kosch M, Lerner M, Bertram H, Lemke D, Oberleithner H. Stimulation of protein kinase C pathway mediates endocytosis of human nongastric H+-K+-ATPase, ATP1AL1. Am J Physiol Renal Physiol 2002; 283:F335-43. [PMID: 12110518 DOI: 10.1152/ajprenal.00226.2001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The human nongastric H+-K+-ATPase, ATP1AL1, shown to reabsorb K+ in exchange for H+ or Na+, is localized in the luminal plasma membrane of renal epithelial cells. It is presumed that renal H+-K+-ATPases can be regulated by endocytosis. However, little is known about the molecular mechanisms that control plasma membrane expression of renal H+-K+-ATPases. In our study, activation of protein kinase C (PKC) using phorbol esters (phorbol 12-myristate 13-acetate) leads to clathrin-dependent internalization and intracellular accumulation of the ion pump in stably transfected Madin-Darby canine kidney cells. Functional inactivation of the H+-K+-ATPase by PKC activation is shown by intracellular pH measurements. Proton extrusion capacity of ATP1AL1-transfected cells is drastically reduced after phorbol 12-myristate 13-acetate incubation and can be prevented with the PKC blocker bisindolylmaleimide. Ion pump internalization and inactivation are specifically mediated by the PKC pathway, whereas activation of the protein kinase A pathway has no influence. Our results show that the nongastric H+-K+-ATPase is a specific target for the PKC pathway. Therefore, PKC-mediated phosphorylation is a potential regulatory mechanism for apical nongastric H+-K+-ATPase plasma membrane expression.
Collapse
Affiliation(s)
- J Reinhardt
- Institute of Physiology, University of Münster, D-48149 Münster, Germany.
| | | | | | | | | | | |
Collapse
|
33
|
Crambert G, Horisberger JD, Modyanov NN, Geering K. Human nongastric H+-K+-ATPase: transport properties of ATP1al1 assembled with different beta-subunits. Am J Physiol Cell Physiol 2002; 283:C305-14. [PMID: 12055100 DOI: 10.1152/ajpcell.00590.2001] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To investigate whether nongastric H+-K+-ATPases transport Na+ in exchange for K+ and whether different beta-isoforms influence their transport properties, we compared the functional properties of the catalytic subunit of human nongastric H+-K+-ATPase, ATP1al1 (AL1), and of the Na+-K+-ATPase alpha1-subunit (alpha1) expressed in Xenopus oocytes, with different beta-subunits. Our results show that betaHK and beta1-NK can produce functional AL1/beta complexes at the oocyte cell surface that, in contrast to alpha1/beta1 NK and alpha1/betaHK complexes, exhibit a similar apparent K+ affinity. Similar to Na+-K+-ATPase, AL1/beta complexes are able to decrease intracellular Na+ concentrations in Na+-loaded oocytes, and their K+ transport depends on intra- and extracellular Na+ concentrations. Finally, controlled trypsinolysis reveals that beta-isoforms influence the protease sensitivity of AL1 and alpha1 and that AL1/beta complexes, similar to the Na+-K+-ATPase, can undergo distinct K+-Na+- and ouabain-dependent conformational changes. These results provide new evidence that the human nongastric H+-K+-ATPase interacts with and transports Na+ in exchange for K+ and that beta-isoforms have a distinct effect on the overall structural integrity of AL1 but influence its transport properties less than those of the Na+-K+-ATPase alpha-subunit.
Collapse
Affiliation(s)
- Gilles Crambert
- Institute Of Pharmacology And Toxicology of The University, CH-1005 Lausanne, Switzerland
| | | | | | | |
Collapse
|
34
|
McDonough AA, Thompson CB, Youn JH. Skeletal muscle regulates extracellular potassium. Am J Physiol Renal Physiol 2002; 282:F967-74. [PMID: 11997312 DOI: 10.1152/ajprenal.00360.2001] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Maintaining extracellular fluid (ECF) K(+) concentration ([K(+)]) within a narrow range is accomplished by the concerted responses of the kidney, which matches K(+) excretion to K(+) intake, and skeletal muscle, the main intracellular fluid (ICF) store of K(+), which can rapidly buffer ECF [K(+)]. In both systems, homologous P-type ATPase isoforms are key effectors of this homeostasis. During dietary K(+) deprivation, these P-type ATPases are regulated in opposite directions: increased abundance of the H,K-ATPase "colonic" isoform in the renal collecting duct drives active K(+) conservation while decreased abundance of the plasma membrane Na,K-ATPase alpha(2)-isoform leads to the specific shift of K(+) from muscle ICF to ECF. The skeletal muscle response is isoform and muscle specific: alpha(2) and beta(2), not alpha(1) and beta(1), levels are depressed, and fast glycolytic muscles lose >90% alpha(2), whereas slow oxidative muscles lose ~50%; however, both muscle types have the same fall in cellular [K(+)]. To understand the physiological impact, we developed the "K(+) clamp" to assess insulin-stimulated cellular K(+) uptake in vivo in the conscious rat by measuring the exogenous K(+) infusion rate needed to maintain constant plasma [K(+)] during insulin infusion. Using the K(+) clamp, we established that K(+) deprivation leads to near-complete insulin resistance of cellular K(+) uptake and that this insulin resistance can occur before any decrease in plasma [K(+)] or muscle Na(+) pump expression. These studies establish the advantage of combining molecular analyses of P-type ATPase expression with in vivo analyses of cellular K(+) uptake and excretion to determine mechanisms in models of disrupted K(+) homeostasis.
Collapse
Affiliation(s)
- Alicia A McDonough
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9142, USA.
| | | | | |
Collapse
|
35
|
Pestov NB, Korneenko TV, Adams G, Tillekeratne M, Shakhparonov MI, Modyanov NN. Nongastric H-K-ATPase in rodent prostate: lobe-specific expression and apical localization. Am J Physiol Cell Physiol 2002; 282:C907-16. [PMID: 11880279 DOI: 10.1152/ajpcell.00258.2001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The molecular basis of active ion transport in secretory glands such as the prostate is not well characterized. Rat nongastric H-K-ATPase is expressed at high levels in distal colon surface cell apical membranes and thus is referred to as "colonic." Here we show that the ATPase is expressed in rodent prostate complex in a lobe-specific manner. RT-PCR and Western blot analyses indicate that rat nongastric H-K-ATPase alpha-subunit (alpha(ng)) mRNA and protein are present in coagulating gland (anterior prostate) and lateral and dorsal prostate and absent from ventral lobe, whereas Na-K-ATPase alpha-subunit is present in all lobes. RT-PCR analysis shows that Na-K-ATPase alpha(4) and alpha(3) and gastric H-K-ATPase alpha-subunit are not present in significant amounts in all prostate lobes. Relatively low levels of Na-K-ATPase alpha(2) were found in lateral, dorsal, and anterior lobes. alpha(ng) protein expression is anteriodorsolateral: highest in coagulating gland, somewhat lower in dorsal lobe, and even lower in lateral lobe. Na-K-ATPase protein abundance has the reverse order: expression in ventral lobe is higher than in coagulating gland. alpha(ng) protein abundance is higher in coagulating gland than distal colon membranes. Immunohistochemistry shows that in rat and mouse coagulating gland epithelium alpha(ng) protein has an apical polarization and Na-K-ATPase alpha(1) is localized in basolateral membranes. The presence of nongastric H-K-ATPase in rodent prostate apical membranes may indicate its involvement in potassium concentration regulation in secretions of these glands.
Collapse
Affiliation(s)
- Nikolay B Pestov
- Department of Pharmacology, Medical College of Ohio, 3035 Arlington Ave., Toledo, OH 43614, USA
| | | | | | | | | | | |
Collapse
|
36
|
Codina J, Li J, Hong Y, DuBose TD. The gamma-Na+,K+-ATPase subunit assembles selectively with alpha1/beta1-Na+,K+-ATPase but not with the colonic H+,K+-ATPase. Kidney Int 2002; 61:967-74. [PMID: 11849451 DOI: 10.1046/j.1523-1755.2002.00189.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The ubiquitous Na+-pump (Na+,K+-ATPase) assembles as a heterodimer of composition alpha/beta in some nephron segments, while in other segments it may exist as a heterotrimer of composition alpha/beta/gamma. The gamma-subunit has been reported to increase the affinity of the Na+-pump for adenosine 5'-triphosphate (ATP), and decrease affinity for both Na+ and K+. The alpha-subunit of the colonic H+,K+-ATPase (cHK) shares 75% sequence similarity with alpha1-Na+,K+-ATPase (alpha1) and assembles with beta1-Na+,K+-ATPase (beta1) in distal colon and renal medulla. Differences in pharmacological properties have been ascribed to when heterologously expressed function has been compared to function in vitro. The purpose of this study was to determine if cHK might associate with the gamma-subunit of the Na+,K+-ATPase (gamma) as a possible explanation for these variations in function. METHODS An antibody specific for the gamma was used in coimmunoprecipitation experiments to determine if the gamma assembles stably in vitro with cHK and beta1 in rat renal medulla or distal colon. RESULTS Our results demonstrate that the gamma-subunit assembles specifically with the Na+-pump, but not with cHK. Furthermore, the gamma-subunit assembly was specific for rat kidney and was not observed in distal colon. CONCLUSION Since the gamma-subunit did not assemble with the cHK/beta1 complex, gamma-subunit assembly cannot explain those variations in ex vivo and in vitro pharmacologic properties ascribed to cHK.
Collapse
Affiliation(s)
- Juan Codina
- Department of Internal Medicine and Kidney Institute, University of Kansas School of Medicine, Kansas City, KS, USA
| | | | | | | |
Collapse
|
37
|
Zhang W, Kuncewicz T, Higham SC, Kone BC. Structure, promoter analysis, and chromosomal localization of the murine H(+)/K(+)-ATPase alpha 2 subunit gene. J Am Soc Nephrol 2001; 12:2554-2564. [PMID: 11729223 DOI: 10.1681/asn.v12122554] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The H(+)/K(+)-ATPase alpha2 subunit (HK alpha 2) of distal colon and renal collecting ducts plays a critical role in potassium and acid-base homeostasis. The isolation and complete sequence of the murine HK alpha 2 gene are reported. The HK alpha 2 gene contains 23 exons and spans 23.5 kb of genomic DNA. The exon/intron organization is comparable to that of the human ATP1AL1 gene. Primer extension and 5'-rapid amplification of cDNA ends of distal colon RNA were used to map the transcription initiation site. Fluorescence in situ hybridization analysis localized the HK alpha 2 gene to murine chromosome 14C3. Sequence analysis of 7.2 kb of the 5'-flanking region revealed numerous consensus sites for transcription factors, including two potential glucocorticoid response elements. Transient transfection of promoter-luciferase constructs demonstrated strong basal HK alpha 2 promoter activity in renal collecting duct cells but not in fibroblasts or in a medullary thick ascending limb of Henle's loop cell line. Deletion analysis revealed that the proximal 0.2 kb of the promoter was sufficient to confer activity in collecting duct cells. These data should prove important in elucidation of the mechanisms controlling the differential, tissue-specific expression of the HK alpha 2 gene.
Collapse
Affiliation(s)
- Wenzheng Zhang
- Departments of *Internal Medicine and Integrative Biology, Pharmacology, and Physiology, The University of Texas Medical School at Houston, Houston, Texas
| | - Teresa Kuncewicz
- Departments of *Internal Medicine and Integrative Biology, Pharmacology, and Physiology, The University of Texas Medical School at Houston, Houston, Texas
| | - Sandra C Higham
- Departments of *Internal Medicine and Integrative Biology, Pharmacology, and Physiology, The University of Texas Medical School at Houston, Houston, Texas
| | - Bruce C Kone
- Departments of *Internal Medicine and Integrative Biology, Pharmacology, and Physiology, The University of Texas Medical School at Houston, Houston, Texas
| |
Collapse
|
38
|
Spicer Z, Clarke LL, Gawenis LR, Shull GE. Colonic H(+)-K(+)-ATPase in K(+) conservation and electrogenic Na(+) absorption during Na(+) restriction. Am J Physiol Gastrointest Liver Physiol 2001; 281:G1369-77. [PMID: 11705741 DOI: 10.1152/ajpgi.2001.281.6.g1369] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Upregulation of the colonic H(+)-K(+)- ATPase (cHKA) during hyperaldosteronism suggests that it functions in both K(+) conservation and electrogenic Na(+) absorption in the colon when Na(+)-conserving mechanisms are activated. To test this hypothesis, wild-type (cHKA(+/+)) and cHKA-deficient (cHKA(-/-)) mice were fed Na(+)-replete and Na(+)-restricted diets and their responses were analyzed. In both genotypes, Na(+) restriction led to reduced plasma Na(+) and increased serum aldosterone, and mRNAs for the epithelial Na(+) channel (ENaC) beta- and gamma-subunits, channel-inducing factor, and cHKA were increased in distal colon. Relative to wild-type controls, cHKA(-/-) mice on a Na(+)-replete diet had elevated fecal K(+) excretion. Dietary Na(+) restriction led to increased K(+) excretion in knockout but not in wild-type mice. The amiloride-sensitive, ENaC-mediated short-circuit current in distal colon was significantly reduced in knockout mice maintained on either the Na(+)-replete or Na(+)-restricted diet. These results demonstrate that cHKA plays an important role in K(+) conservation during dietary Na(+) restriction and suggest that cHKA-mediated K(+) recycling across the apical membrane is required for maximum electrogenic Na(+) absorption.
Collapse
Affiliation(s)
- Z Spicer
- Department of Molecular Genetics, Biochemistry and Microbiology, The University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0524, USA
| | | | | | | |
Collapse
|
39
|
Abstract
Na,K-ATPase and gastric and nongastric H,K-ATPases are the only P-type ATPases of higher organisms that are oligomeric and are associated with a beta subunit, which is obligatory for expression and function of enzymes. Topogenesis studies suggest that beta subunits have a fundamental and unique role in K+-transporting P-type ATPases in that they facilitate the correct membrane integration and packing of the catalytic a subunit of these P-type ATPases, which is necessary for their resistance to cellular degradation, their acquisition of functional properties, and their routing to the cell surface. In addition to this chaperone function, beta subunits also participate in the determination of intrinsic transport properties of Na,K- and H,K-ATPases. Increasing experimental evidence suggests that beta assembly is a highly ordered, beta isoform-specific process, which is mediated by multiple interaction sites that contribute in a coordinate, multistep process to the structural and functional maturation of Na,K- and H,K-ATPases.
Collapse
Affiliation(s)
- K Geering
- Institute of Pharmacology and Toxicology, University of Lausanne, Switzerland.
| |
Collapse
|
40
|
Adams G, Tillekeratne M, Yu C, Pestov NB, Modyanov NN. Catalytic function of nongastric H,K-ATPase expressed in Sf-21 insect cells. Biochemistry 2001; 40:5765-76. [PMID: 11341842 DOI: 10.1021/bi010191y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We previously demonstrated that the alpha-subunit of human nongastric H,K-ATPase (Atp1al1) can assemble with the gastric H,K-ATPase beta-subunit (betaHK) into an active ion pump upon coexpression in Xenopus oocytes. To gain insight into enzymatic functions, we have analyzed the Atp1al1-betaHK complex using a baculovirus expression system. The efficient formation of the functional Atp1al1-betaHK complex in membranes of Sf-21 insect cells was obtained upon co-infection with recombinant baculoviruses expressing Atp1al1 and betaHK. Expression of either protein alone did not produce active ATPase. The effects of K(+), Na(+), pH, and ATP and inhibitors on ATPase activity of the recombinant Atp1al1-betaHK complex were analyzed. The Atp1al1-betaHK complex was shown to exhibit significant ATPase activity in nominally K(+)-free medium. The addition of K(+) stimulated the ATP hydrolysis up to 3-fold with K(m) approximately 116 microM K(+). The ATPase activity was moderately sensitive to ouabain and to SCH 28080 with apparent K(i) values in K(+)-free medium of approximately 64 microM and approximately 93 microM, respectively. Potassium exhibited strong antagonism toward both inhibitors. Assays of the ouabain-sensitive ATPase activity revealed inhibitory effects of Na(+) with the apparent K(i) of approximately 24 mM in the absence of added K(+) and with K(i) within the range of 60-70 mM in the presence of > or = 1 mM K(+). Thus, the human nongastric H,K-ATPase represented by the recombinant Atp1al1-betaHK complex exhibits enzymatic properties of K(+)-dependent ATPase sensitive to ouabain, SCH 28080, and Na(+). It differs from Na,K-ATPase in cation dependence and differs from gastric H,K-ATPase and Na,K-ATPase in sensitivity to inhibitors.
Collapse
Affiliation(s)
- G Adams
- Department of Pharmacology, Medical College of Ohio, Toledo, Ohio 43614-5804, USA
| | | | | | | | | |
Collapse
|
41
|
Laroche-Joubert N, Marsy S, Doucet A. Cellular origin and hormonal regulation of K(+)-ATPase activities sensitive to Sch-28080 in rat collecting duct. Am J Physiol Renal Physiol 2000; 279:F1053-9. [PMID: 11097623 DOI: 10.1152/ajprenal.2000.279.6.f1053] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rat collecting ducts exhibit type I or type III K(+)-ATPase activities when animals are fed a normal (NK) or a K(+)-depleted diet (LK). This study aimed at determining functionally the cell origin of these two K(+)-ATPases. For this purpose, we searched for an effect on K(+)-ATPases of hormones that trigger cAMP production in a cell-specific fashion. The effects of 1-deamino-8-D-arginine vasopressin (dD-AVP), calcitonin, and isoproterenol in principal cells, alpha-intercalated cells, and beta-intercalated cells of cortical collecting duct (CCD), respectively, and of dD-AVP and glucagon in principal and alpha-intercalated cells of outer medullary collecting duct (OMCD), respectively, were examined. In CCDs, K(+)-ATPase was stimulated by calcitonin and isoproterenol in NK rats (type I K(+)-ATPase) and by dD-AVP in LK rats (type III K(+)-ATPase). In OMCDs, dD-AVP and glucagon stimulated type III but not type I K(+)-ATPase. These hormone effects were mimicked by the cAMP-permeant analog dibutyryl-cAMP. In conclusion, in NK rats, cAMP stimulates type I K(+)-ATPase activity in alpha- and beta-intercalated CCD cells, whereas in LK rats it stimulates type III K(+)-ATPase in principal cells of both CCD and OMCD and in OMCD intercalated cells.
Collapse
Affiliation(s)
- N Laroche-Joubert
- Laboratoire de Biologie Intégrée des Cellules Rénales, Service de Biologie Cellulaire, Commissariat à l'Energie Atomique, Saclay, Unité de Recherche Associée 1859, Centre National de la Recherche Scientifique, 91191 Gif-sur-Yvette Cedex, France
| | | | | |
Collapse
|
42
|
Codina J, Cardwell J, Gitomer JJ, Cui Y, Kone BC, Dubose TD. Sch-28080 depletes intracellular ATP selectively in mIMCD-3 cells. Am J Physiol Cell Physiol 2000; 279:C1319-26. [PMID: 11029278 DOI: 10.1152/ajpcell.2000.279.5.c1319] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two H(+)-K(+)-ATPase isoforms are present in kidney: the gastric, highly sensitive to Sch-28080, and the colonic, partially sensitive to ouabain. Upregulation of Sch-28080-sensitive H(+)-K(+)-ATPase, or "gastric" H(+)-K(+)-ATPase, has been demonstrated in hypokalemic rat inner medullary collecting duct cells (IMCDs). Nevertheless, only colonic H(+)-K(+)-ATPase mRNA and protein abundance increase in this condition. This study was designed to determine whether Sch-28080 inhibits transporters other than the gastric H(+)-K(+)-ATPase. In the presence of bumetanide, Sch-28080 (200 microM) and ouabain (2 mM) inhibited (86)Rb(+) uptake (>90%). That (86)Rb(+) uptake was almost completely abolished by Sch-28080 indicates an effect of this agent on the Na(+)-K(+)-ATPase. ATPase assays in membranes, or lysed cells, demonstrated sensitivity to ouabain but not Sch-28080. Thus the inhibitory effect of Sch-28080 was dependent on cell integrity. (86)Rb(+)-uptake studies without bumetanide demonstrated that ouabain inhibited activity by only 50%. Addition of Sch-28080 (200 microM) blocked all residual activity. Intracellular ATP declined after Sch-28080 (200 microM) but recovered after removal of this agent. In conclusion, high concentrations of Sch-28080 inhibit K(+)-ATPase activity in mouse IMCD-3 (mIMCD-3) cells as a result of ATP depletion.
Collapse
Affiliation(s)
- J Codina
- Department of Internal Medicine, University of Kansas School of Medicine, Kansas City, Kansas 66160-7350, USA
| | | | | | | | | | | |
Collapse
|
43
|
Geering K, Crambert G, Yu C, Korneenko TV, Pestov NB, Modyanov NN. Intersubunit interactions in human X,K-ATPases: role of membrane domains M9 and M10 in the assembly process and association efficiency of human, nongastric H,K-ATPase alpha subunits (ATP1al1) with known beta subunits. Biochemistry 2000; 39:12688-98. [PMID: 11027149 DOI: 10.1021/bi0009791] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Na,K- and H,K-ATPase (X,K-ATPase) alpha subunits need association with a beta subunit for their maturation, but the authentic beta subunit of nongastric H,K-ATPase alpha subunits has not been identified. To better define alpha-beta interactions in these ATPases, we coexpressed human, nongastric H,K-ATPase alpha (AL1) and Na,K-ATPase alpha1 (alpha1NK) as well as AL1-alpha1 and alpha1-AL1 chimeras, which contain exchanged M9 and M10 membrane domains, together with each of the known beta subunits in Xenopus oocytes and followed their resistance to cellular and proteolytic degradation and their ER exit. We show that all beta subunits (gastric betaHK, beta1NK, beta2NK, beta3NK, or Bufo bladder beta) can associate efficiently with alpha1NK, but only gastric betaHK, beta2NK, and Bufo bladder beta can form stably expressed AL1-beta complexes that can leave the ER. The trypsin resistance and the forces of subunit interaction, probed by detergent resistance, are lower for AL1-beta complexes than for alpha1NK-beta complexes. Furthermore, chimeric alpha1-AL1 can be stabilized by beta subunits, but alpha1-AL1-gastric betaHK complexes are retained in the ER. On the other hand, chimeric AL1-alpha1 cannot be stabilized by any beta subunit. In conclusion, these results indicate that (1) none of the known beta subunits is the real partner subunit of AL1 but an as yet unidentified, authentic beta should have structural features resembling gastric betaHK, beta2NK, or Bufo bladder beta and (2) beta-mediated maturation of alpha subunits is a multistep process which depends on the membrane insertion properties of alpha subunits as well as on several discrete events of intersubunit interactions.
Collapse
Affiliation(s)
- K Geering
- Institut de Pharmacologie et de Toxicologie de l'Université, rue du Bugnon 27, CH-1005 Lausanne, Switzerland.
| | | | | | | | | | | |
Collapse
|
44
|
Sangan P, Brill SR, Sangan S, Forbush B, Binder HJ. Basolateral K-Cl cotransporter regulates colonic potassium absorption in potassium depletion. J Biol Chem 2000; 275:30813-6. [PMID: 10878016 DOI: 10.1074/jbc.m003931200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Active potassium absorption in the rat distal colon is electroneutral, Na(+)-independent, partially chloride-dependent, and energized by an apical membrane H,K-ATPase. Both dietary sodium and dietary potassium depletion substantially increase active potassium absorption. We have recently reported that sodium depletion up-regulates H,K-ATPase alpha-subunit mRNA and protein expression, whereas potassium depletion up-regulates H,K-ATPase beta-subunit mRNA and protein expression. Because overall potassium absorption is non-conductive, K-Cl cotransport (KCC) at the basolateral membrane may also be involved in potassium absorption. Although KCC1 has not been cloned from the colon, we established, in Northern blot analysis with mRNA from the rat distal colon using rabbit kidney KCC1 cDNA as a probe, the presence of an expected size mRNA in the rat colon. This KCC1 mRNA is substantially increased by potassium depletion but only minimally by sodium depletion. KCC1-specific antibody identified a 155-kDa protein in rat colonic basolateral membrane. Potassium depletion but not sodium depletion resulted in an increase in KCC1 protein expression in basolateral membrane. The increase of colonic KCC1 mRNA abundance and KCC1 protein expression in potassium depletion of the rat colonic basolateral membrane suggests that K-Cl cotransporter: 1) is involved in transepithelial potassium absorption and 2) regulates the increase in potassium absorption induced by dietary potassium depletion. We conclude that active potassium absorption in the rat distal colon involves the coordinated regulation of both apical membrane H,K-ATPase and basolateral membrane KCC1 protein.
Collapse
Affiliation(s)
- P Sangan
- Departments of Internal Medicine and Cellular and Molecular Physiology, Yale University, New Haven, Connecticut 06520, USA
| | | | | | | | | |
Collapse
|
45
|
Reinhardt J, Grishin AV, Oberleithner H, Caplan MJ. Differential localization of human nongastric H(+)-K(+)-ATPase ATP1AL1 in polarized renal epithelial cells. Am J Physiol Renal Physiol 2000; 279:F417-25. [PMID: 10966921 DOI: 10.1152/ajprenal.2000.279.3.f417] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The human H(+)-K(+)-ATPase, ATP1AL1, belongs to the subgroup of nongastric, K(+)-transporting ATPases. In concert with the structurally related gastric H(+)-K(+)-ATPase, it plays a major role in K(+) reabsorption in various tissues, including colon and kidney. Physiological and immunocytochemical data suggest that the functional heteromeric ion pumps are usually found in the apical plasma membranes of renal epithelial cells. However, the low expression levels of characteristic nongastric ion pumps makes it difficult to verify their spatial distribution in vivo. To investigate the sorting behavior of ATP1AL1, we expressed this pump by stable transfection in MDCK and LLC-PK(1) renal epithelial cell lines. Stable interaction of ATP1AL1 with either the endogenous Na(+)-K(+)-ATPase beta-subunit or the gastric H(+)-K(+)-ATPase beta-subunit was tested by confocal immunofluorescence microscopy and surface biotinylation. In cells transfected with ATP1AL1 alone, the alpha-subunit accumulated intracellularly, consistent with its inability to assemble and travel to the plasma membrane with the endogenous Na(+)-K(+)-ATPase beta-subunit. Cotransfection of ATP1AL1 with the gastric H(+)-K(+)-ATPase beta-subunit resulted in plasma membrane localization of both pump subunits. In cotransfected MDCK cells the heteromeric ion pump was predominantly polarized to the apical plasma membrane. Functional expression of ATP1AL1 was confirmed by (86)Rb(+) uptake measurements. In contrast, cotransfected LLC-PK(1) cells accumulate ATP1AL1 at the lateral membrane. The distinct polarization of ATP1AL1 indicates that the alpha-subunit encodes sorting information that is differently interpreted by cell type-specific sorting mechanisms.
Collapse
Affiliation(s)
- J Reinhardt
- Department of Physiology, University of Münster, 48149 Münster, Germany
| | | | | | | |
Collapse
|
46
|
Rajendran VM, Sangan P, Geibel J, Binder HJ. Ouabain-sensitive H,K-ATPase functions as Na,K-ATPase in apical membranes of rat distal colon. J Biol Chem 2000; 275:13035-40. [PMID: 10777607 DOI: 10.1074/jbc.275.17.13035] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Na,K-ATPase activity has been identified in the apical membrane of rat distal colon, whereas ouabain-sensitive and ouabain-insensitive H,K-ATPase activities are localized solely to apical membranes. This study was designed to determine whether apical membrane Na,K-ATPase represented contamination of basolateral membranes or an alternate mode of H,K-ATPase expression. An antibody directed against the H, K-ATPase alpha subunit (HKcalpha) inhibited apical Na,K-ATPase activity by 92% but did not alter basolateral membrane Na,K-ATPase activity. Two distinct H,K-ATPase isoforms exist; one of which, the ouabain-insensitive HKcalpha, has been cloned. Because dietary sodium depletion markedly increases ouabain-insensitive active potassium absorption and HKcalpha mRNA and protein expression, Na, K-ATPase and H,K-ATPase activities and protein expression were determined in apical membranes from control and sodium-depleted rats. Sodium depletion substantially increased ouabain-insensitive H, K-ATPase activity and HKcalpha protein expression by 109-250% but increased ouabain-sensitive Na,K-ATPase and H,K-ATPase activities by only 30% and 42%, respectively. These studies suggest that apical membrane Na,K-ATPase activity is an alternate mode of ouabain-sensitive H,K-ATPase and does not solely represent basolateral membrane contamination.
Collapse
Affiliation(s)
- V M Rajendran
- Department of Internal Medicine, Yale University, New Haven, Connecticut 06520, USA
| | | | | | | |
Collapse
|
47
|
Levine DZ, Iacovitti M, Luck B, Hincke MT, Burns KD, Fryer JN. Surviving rat distal tubule bicarbonate reabsorption: effects of chronic AT(1) blockade. Am J Physiol Renal Physiol 2000; 278:F476-83. [PMID: 10710552 DOI: 10.1152/ajprenal.2000.278.3.f476] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To determine the in vivo effects of chronic ANG II type 1 (AT(1))-receptor blockade by losartan (Los) on enhanced unidirectional bicarbonate reabsorption (J(HCO(3))) of surviving distal tubules, nephrectomized rats drank either water or a solution of Los, 7 days before microperfusion. J(HCO(3)) was suppressed by 50% after Los without further reduction by 5 nM concanamycin A (Conc), suggesting that Los suppresses all Conc-sensitive H(+)-ATPase pumping. Indeed, ultrastructural analysis of A-type intercalated cells revealed a 50% reduction of H(+)-ATPase immunogold labeling of the apical plasma membrane, whereas Western blotting showed that H(+)-ATPase protein levels were also reduced by one-half by Los treatment. To identify other transporters sustaining J(HCO(3)), we perfused three inhibitors simultaneously [5-(N, N-dimethyl) amiloride hydrochloride, Conc, Schering 28080] with or without prior Los treatment: J(HCO(3)) was unchanged despite marked reduction of water reabsorption. We conclude enhanced distal tubule J(HCO(3)) of surviving nephrons is largely mediated by AT(1) receptor-dependent synthesis and insertion of apical H(+)-ATPase pumps in A-type intercalated cells.
Collapse
MESH Headings
- Absorption
- Angiotensin Receptor Antagonists
- Animals
- Anti-Bacterial Agents/pharmacology
- Bicarbonates/metabolism
- Blotting, Western
- Enzyme Inhibitors/pharmacology
- Immunohistochemistry
- Kidney Tubules, Distal/cytology
- Kidney Tubules, Distal/metabolism
- Kidney Tubules, Distal/ultrastructure
- Losartan/pharmacology
- Macrolides
- Male
- Microscopy, Electron
- Nephrectomy
- Proton-Translocating ATPases/antagonists & inhibitors
- Proton-Translocating ATPases/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
Collapse
Affiliation(s)
- D Z Levine
- Department of Medicine, Division of Nephrology, University of Ottawa and Ottawa Hospital, Ottawa, Ontario, Canada K1H 8M5
| | | | | | | | | | | |
Collapse
|
48
|
Frank AE, Wingo CS, Weiner ID. Effects of ammonia on bicarbonate transport in the cortical collecting duct. Am J Physiol Renal Physiol 2000; 278:F219-26. [PMID: 10662726 DOI: 10.1152/ajprenal.2000.278.2.f219] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Both acidosis and hypokalemia stimulate renal ammoniagenesis, and both regulate urinary proton and potassium excretion. We hypothesized that ammonia might play an important role in this processing by stimulating H(+)-K(+)-ATPase-mediated ion transport. Rabbit cortical collecting ducts (CCD) were studied using in vitro microperfusion, bicarbonate reabsorption was measured using microcalorimetry, and intracellular pH (pH(i)) was measured using the fluorescent, pH-sensitive dye, 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Ammonia caused a concentration-dependent increase in net bicarbonate reabsorption that was inhibited by luminal addition of either of the H(+)-K(+)-ATPase inhibitors, Sch-28080 or ouabain. The stimulation of net bicarbonate reabsorption was not mediated through apical H(+)-ATPase, basolateral Na(+)-K(+)-ATPase, or luminal electronegativity. Although ammonia caused intracellular acidification, similar changes in pH(i) induced by inhibiting basolateral Na(+)/H(+) exchange did not alter net bicarbonate reabsorption. We conclude that ammonia regulates CCD proton and potassium transport, at least in part, by stimulating apical H(+)-K(+)-ATPase.
Collapse
Affiliation(s)
- A E Frank
- Division of Nephrology, Gainesville Veterans Affairs Medical Center, Gainesville, Florida 32610-0224, USA
| | | | | |
Collapse
|
49
|
Sangan P, Thevananther S, Sangan S, Rajendran VM, Binder HJ. Colonic H-K-ATPase alpha- and beta-subunits express ouabain-insensitive H-K-ATPase. Am J Physiol Cell Physiol 2000; 278:C182-9. [PMID: 10644526 DOI: 10.1152/ajpcell.2000.278.1.c182] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Active K absorption in the rat distal colon is energized by an apical H-K-ATPase, a member of the gene family of P-type ATPases. The H-K-ATPase alpha-subunit (HKcalpha) has been cloned and characterized (together with the beta-subunit of either Na-K-ATPase or gastric H-K-ATPase) in Xenopus oocytes as ouabain-sensitive (86)Rb uptake. In contrast, HKcalpha, when expressed in Sf9 cells without a beta-subunit, yielded evidence of ouabain-insensitive H-K-ATPase. Because a beta-subunit (HKcbeta) has recently been cloned from rat colon, this present study was initiated to determine whether H-K-ATPase and its sensitivity to ouabain are expressed when these two subunits (HKcalpha and HKcbeta) are transfected into a mammalian cell expression system. Transfection of HEK-293 cells with HKcalpha and HKcbeta cDNAs resulted in the expression of HKcalpha and HKcbeta proteins and their delivery to plasma membranes. H-K-ATPase activity was identified in crude plasma membranes prepared from transfected cells and was 1) saturable as a function of increasing K concentration with a K(m) for K of 0.63 mM; 2) inhibited by orthovanadate; and 3) insensitive to both ouabain and Sch-28080. In parallel transfection studies with HKcalpha and Na-K-ATPase beta1 cDNAs and with HKcalpha cDNA alone, there was expression of ouabain-insensitive H-K-ATPase activity that was 60% and 21% of that in HKcalpha/HKcbeta cDNA transfected cells, respectively. Ouabain-insensitive (86)Rb uptake was also identified in cells transfected with HKcalpha and HKcbeta cDNAs. These studies establish that HKcalpha cDNA with HKcbeta cDNA express ouabain-insensitive H-K-ATPase similar to that identified in rat distal colon.
Collapse
Affiliation(s)
- P Sangan
- Departments of Internal Medicine and Pediatrics, Yale University, New Haven, Connecticut 06520-8019, USA
| | | | | | | | | |
Collapse
|
50
|
Abstract
The H+,K+-ATPases comprise a group of integral membrane proteins that belong to the X+,K+-ATPase subfamily of P-type cation-transporting ATPases. Although these H+,K+-ATPase isoforms share approximately 60-70% amino acid identity, they exhibit discrete kinetic and pharmacological properties when expressed in heterologous systems. HK alpha2 has been categorized by its insensitivity to Sch-28080, an inhibitor of the gastric H+,K+-ATPase, and partial sensitivity to ouabain, an inhibitor of the Na+,K+-ATPase. This functional profile contrasts with the pharmacological sensitivities ascribed to HK alpha2 in transport studies in rat isolated medullary collecting ducts perfused in vitro and in mouse medullary collecting duct cell lines. HK alpha2 mRNA and protein abundance appears to be both tissue and site-specifically upregulated in response to chronic hypokalemia. This regulatory response has been localized to the outer and inner medulla. To reconcile these expressed sensitivities to those reported in vitro in isolated tubules and cells in culture, it would be necessary to invoke modification of the pharmacologic insensitivity of the colonic H+,K+-ATPase to Sch-28080. Although a 'unique' beta-subunit has been reported recently, this beta-subunit (beta(c)) is identical at the amino acid level to the recently cloned beta3-Na+,K+-ATPase. Moreover, while HK alpha2 can assemble indiscriminately with any X+,K+-ATPase beta-subunit, HK alpha2 has been reported to assemble stably with beta1-Na+,K+-ATPase in the renal medulla and in the distal colon. It remains conceivable that subunit assembly could be tissue specific and might respond to different physiological and pathophysiological stimuli. Furthermore, recent studies have suggested that the H+,K+-ATPase is both Na+-dependent and localized to the apical membrane in the distal colon. Therefore, future studies will need to resolve these discrepancies by determining if a unique, yet undiscovered H+,K+-ATPase isoform exists in kidney, or if post-translational modifications of the alpha- and/or beta-subunits could account for these functional diversities.
Collapse
Affiliation(s)
- T D DuBose
- Department of Internal Medicine, University of Texas-Houston Medical School 77030, USA.
| | | | | |
Collapse
|