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Nickerson AJ, Sheng S, Cox NA, Szekely KG, Marciszyn AL, Lam T, Chen J, Gingras S, Kashlan OB, Kirabo A, Hughey RP, Ray EC, Kleyman TR. Loss of the alpha subunit distal furin cleavage site blunts ENaC activation following Na + restriction. J Physiol 2024; 602:4309-4326. [PMID: 39196791 PMCID: PMC11384278 DOI: 10.1113/jp286559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 07/17/2024] [Indexed: 08/30/2024] Open
Abstract
Epithelial Na+ channels (ENaCs) are activated by proteolysis of the α and γ subunits at specific sites flanking embedded inhibitory tracts. To examine the role of α subunit proteolysis in channel activation in vivo, we generated mice lacking the distal furin cleavage site in the α subunit (αF2M mice). On a normal Na+ control diet, no differences in ENaC protein abundance in kidney or distal colon were noted between wild-type (WT) and αF2M mice. Patch-clamp analyses revealed similar levels of ENaC activity in kidney tubules, while no physiologically relevant differences in blood chemistry or aldosterone levels were detected. Male αF2M mice did exhibit diminished ENaC activity in the distal colon, as measured by amiloride-sensitive short-circuit current (ISC). Following dietary Na+ restriction, WT and αF2M mice had similar natriuretic and colonic ISC responses to amiloride. However, single-channel activity was significantly lower in kidney tubules from Na+-restricted αF2M mice compared with WT littermates. ENaC α and γ subunit expression in kidney and distal colon were also enhanced in Na+-restricted αF2M vs. WT mice, in association with higher aldosterone levels. These data provide evidence that disrupting α subunit proteolysis impairs ENaC activity in vivo, requiring compensation in response to Na+ restriction. KEY POINTS: The epithelial Na+ channel (ENaC) is activated by proteolytic cleavage in vitro, but key questions regarding the role of ENaC proteolysis in terms of whole-animal physiology remain to be addressed. We studied the in vivo importance of this mechanism by generating a mouse model with a genetic disruption to a key cleavage site in the ENaC's α subunit (αF2M mice). We found that αF2M mice did not exhibit a physiologically relevant phenotype under normal dietary conditions, but have impaired ENaC activation (channel open probability) in the kidney during salt restriction. ENaC function at the organ level was preserved in salt-restricted αF2M mice, but this was associated with higher aldosterone levels and increased expression of ENaC subunits, suggesting compensation was required to maintain homeostasis. These results provide the first evidence that ENaC α subunit proteolysis is a key regulator of channel activity in vivo.
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Affiliation(s)
- Andrew J Nickerson
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Shaohu Sheng
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Natalie A Cox
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Kennedy G Szekely
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Allison L Marciszyn
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Tracey Lam
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jingxin Chen
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Sebastien Gingras
- Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Ossama B Kashlan
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Annet Kirabo
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Rebecca P Hughey
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Evan C Ray
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Schork A, Vogel E, Bohnert BN, Essigke D, Wörn M, Fischer I, Heyne N, Birkenfeld AL, Artunc F. Amiloride versus furosemide for the treatment of edema in patients with nephrotic syndrome: A pilot study (AMILOR). Acta Physiol (Oxf) 2024; 240:e14183. [PMID: 38822593 DOI: 10.1111/apha.14183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 05/14/2024] [Accepted: 05/18/2024] [Indexed: 06/03/2024]
Abstract
AIM In rodent models of nephrotic syndrome (NS), edema formation was prevented by blockade of the epithelial sodium channel ENaC with amiloride. However, apart from case reports, there is no evidence favoring ENaC blockade in patients with NS. METHODS The monocentric randomized controlled AMILOR study investigated the antiedematous effect of amiloride (starting dose 5 mg/day, max. 15 mg/day) in comparison to standard therapy with the loop diuretic furosemide (40 mg/day, max. 120 mg/day) over 16 days. Overhydration (OH) was measured by bioimpedance spectroscopy (BCM, Fresenius). Depending on the OH response, diuretic dose was adjusted on days 2, 5, 8 and 12, and if necessary, hydrochlorothiazide (HCT) was added from d8 (12.5 mg/day, max. 25 mg/day). The primary endpoint was the decrease in OH on d8. The study was terminated prematurely due to insufficient recruitment and a low statistical power due to a low actual effect size. RESULTS Median baseline OH was +26.4 (interquartile range 15.5-35.1)% extracellular water (ECW) in the amiloride arm and + 27.9 (24.1-29.4)% ECW in the furosemide arm and decreased by 1.95 (0.80-6.40) and 5.15 (0.90-8.30)% ECW after 8 days, respectively, and by 10.10 (1.30-14.40) and 7.40 (2.80-10.10)% ECW after 16 days, respectively. OH decrease on d8 and d16 was not significantly different between both arms. CONCLUSION The AMILOR study is the first randomized controlled pilot study suggesting a similar antiedematous effect as furosemide. Further studies are required to better define the role of amiloride in NS (EudraCT 2019-002607-18).
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Affiliation(s)
- Anja Schork
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Elisabeth Vogel
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Bernhard N Bohnert
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Daniel Essigke
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Matthias Wörn
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Imma Fischer
- Institute for Clinical Epidemiology and Applied Biometry, University Hospital Tübingen, Tübingen, Germany
| | - Nils Heyne
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Andreas L Birkenfeld
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Ferruh Artunc
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
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Huang N, Wang Q, Bernard RB, Chen CY, Hu JM, Wang JK, Chan KS, Johnson MD, Lin CY. SPINT2 mutations in the Kunitz domain 2 found in SCSD patients inactivate HAI-2 as prostasin inhibitor via abnormal protein folding and N-glycosylation. Hum Mol Genet 2024; 33:752-767. [PMID: 38271183 PMCID: PMC11031362 DOI: 10.1093/hmg/ddae005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 11/30/2023] [Accepted: 01/05/2024] [Indexed: 01/27/2024] Open
Abstract
Mutations in the Kunitz-type serine protease inhibitor HAI-2, encoded by SPINT2, are responsible for the pathogenesis of syndromic congenital sodium diarrhea (SCSD), an intractable secretory diarrhea of infancy. Some of the mutations cause defects in the functionally required Kunitz domain 1 and/or subcellular targeting signals. Almost all SCSD patients, however, harbor SPINT2 missense mutations that affect the functionally less important Kunitz domain 2. How theses single amino acid substitutions inactivate HAI-2 was, here, investigated by the doxycycline-inducible expression of three of these mutants in HAI-2-knockout Caco-2 human colorectal adenocarcinoma cells. Examining protein expressed from these HAI-2 mutants reveals that roughly 50% of the protein is synthesized as disulfide-linked oligomers that lose protease inhibitory activity due to the distortion of the Kunitz domains by disarrayed disulfide bonding. Although the remaining protein is synthesized as monomers, its glycosylation status suggests that the HAI-2 monomer remains in the immature, lightly glycosylated form, and is not converted to the heavily glycosylated mature form. Heavily glycosylated HAI-2 possesses full anti-protease activity and appropriate subcellular targeting signals, including the one embedded in the complex-type N-glycan. As predicted, these HAI-2 mutants cannot suppress the excessive prostasin proteolysis caused by HAI-2 deletion. The oligomerization and glycosylation defects have also been observed in a colorectal adenocarcinoma line that harbors one of these SPINT2 missense mutations. Our study reveals that the abnormal protein folding and N-glycosylation can cause widespread HAI-2 inactivation in SCSD patents.
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Affiliation(s)
- Nanxi Huang
- Lombardi Comprehensive Cancer Center, Department of Oncology, Georgetown University, 3970 Reservoir Road NW W422 New Research Building, Washington DC 20057, United States
| | - Qiaochu Wang
- Lombardi Comprehensive Cancer Center, Department of Oncology, Georgetown University, 3970 Reservoir Road NW W422 New Research Building, Washington DC 20057, United States
| | - Robert B Bernard
- Lombardi Comprehensive Cancer Center, Department of Oncology, Georgetown University, 3970 Reservoir Road NW W422 New Research Building, Washington DC 20057, United States
| | - Chao-Yang Chen
- School of Medicine, National Defense Medical Center, No. 161, sec. 6, Minquan E. Road, Neihu Dist. Taipei City 11490, Taiwan, ROC
- Division of Colorectal Surgery, Department of Surgery, Tri-Service General Hospital, No. 325, Sec. 2, Chenggon Road, Neihu Dist. Taipei City 114202, Taiwan, ROC
| | - Je-Ming Hu
- School of Medicine, National Defense Medical Center, No. 161, sec. 6, Minquan E. Road, Neihu Dist. Taipei City 11490, Taiwan, ROC
- Division of Colorectal Surgery, Department of Surgery, Tri-Service General Hospital, No. 325, Sec. 2, Chenggon Road, Neihu Dist. Taipei City 114202, Taiwan, ROC
- Graduate Institute of Medical Sciences, National Defense Medical Center, No. 161, sec. 6, Minquan E. Neihu Dist. Taipei City 11490, Taiwan, ROC
| | - Jehng-Kang Wang
- Department of Biochemistry, National Defense Medical Center, No. 161, sec. 6, Minquan E. Road, Taipei City, 11490, Taiwan, ROC
| | - Khee-Siang Chan
- Department of Intensive Care Medicine, Chi Mei Medical Center, No. 901, Zhonghua Road, Yongkang Dist., Tainan City, 71004, Taiwan, ROC
| | - Michael D Johnson
- Lombardi Comprehensive Cancer Center, Department of Oncology, Georgetown University, 3970 Reservoir Road NW W422 New Research Building, Washington DC 20057, United States
| | - Chen-Yong Lin
- Lombardi Comprehensive Cancer Center, Department of Oncology, Georgetown University, 3970 Reservoir Road NW W422 New Research Building, Washington DC 20057, United States
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Sure F, Einsiedel J, Gmeiner P, Duchstein P, Zahn D, Korbmacher C, Ilyaskin AV. The small molecule activator S3969 stimulates the epithelial sodium channel by interacting with a specific binding pocket in the channel's β-subunit. J Biol Chem 2024; 300:105785. [PMID: 38401845 PMCID: PMC11065748 DOI: 10.1016/j.jbc.2024.105785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 01/13/2024] [Accepted: 02/19/2024] [Indexed: 02/26/2024] Open
Abstract
The epithelial sodium channel (ENaC) is essential for mediating sodium absorption in several epithelia. Its impaired function leads to severe disorders, including pseudohypoaldosteronism type 1 and respiratory distress. Therefore, pharmacological ENaC activators have potential therapeutic implications. Previously, a small molecule ENaC activator (S3969) was developed. So far, little is known about molecular mechanisms involved in S3969-mediated ENaC stimulation. Here, we identified an S3969-binding site in human ENaC by combining structure-based simulations with molecular biological methods and electrophysiological measurements of ENaC heterologously expressed in Xenopus laevis oocytes. We confirmed a previous observation that the extracellular loop of β-ENaC is essential for ENaC stimulation by S3969. Molecular dynamics simulations predicted critical residues in the thumb domain of β-ENaC (Arg388, Phe391, and Tyr406) that coordinate S3969 within a binding site localized at the β-γ-subunit interface. Importantly, mutating each of these residues reduced (R388H; R388A) or nearly abolished (F391G; Y406A) the S3969-mediated ENaC activation. Molecular dynamics simulations also suggested that S3969-mediated ENaC stimulation involved a movement of the α5 helix of the thumb domain of β-ENaC away from the palm domain of γ-ENaC. Consistent with this, the introduction of two cysteine residues (βR437C - γS298C) to form a disulfide bridge connecting these two domains prevented ENaC stimulation by S3969 unless the disulfide bond was reduced by DTT. Finally, we demonstrated that S3969 stimulated ENaC endogenously expressed in cultured human airway epithelial cells (H441). These new findings may lead to novel (patho-)physiological and therapeutic concepts for disorders associated with altered ENaC function.
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Affiliation(s)
- Florian Sure
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jürgen Einsiedel
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Peter Gmeiner
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Patrick Duchstein
- Theoretical Chemistry/Computer Chemistry Center (CCC), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Dirk Zahn
- Theoretical Chemistry/Computer Chemistry Center (CCC), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Christoph Korbmacher
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Alexandr V Ilyaskin
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
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Ortmann LA, Nandi S, Li YL, Zheng H, Patel KP. Activation of renal epithelial Na + channels (ENaC) in infants with congenital heart disease. Front Pediatr 2024; 12:1338672. [PMID: 38379911 PMCID: PMC10876900 DOI: 10.3389/fped.2024.1338672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 01/25/2024] [Indexed: 02/22/2024] Open
Abstract
Introduction This study was designed to measure the concentration and activity of urinary proteases that activate renal epithelial sodium channel (ENaC) mediated Na+ transport in infants with congenital heart disease, a potential mechanism for fluid retention. Methods Urine samples from infants undergoing cardiac surgery were collected at three time points: T1) pre-operatively, T2) 6-8 h after surgery, and T3) 24 h after diuretics. Urine was collected from five heathy infant controls. The urine was tested for four proteases and whole-cell patch-clamp testing was conducted in renal collecting duct M-1 cells to test whether patient urine increased Na+ currents consistent with ENaC activation. Results Heavy chain of plasminogen, furin, and prostasin were significantly higher in cardiac patients prior to surgery compared to controls. There was no difference in most proteases before and after surgery. Urine from cardiac patients produced a significantly greater increase in Na+ inward currents compared to healthy controls. Conclusion Urine from infants with congenital heart disease is richer in proteases and has the potential to increase activation of ENaC in the nephron to enhance Na+ reabsorption, which may lead to fluid retention in this population.
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Affiliation(s)
- Laura A. Ortmann
- Department of Pediatrics, University of Nebraska Medical Center, Omaha, NE, United States
| | - Shyam Nandi
- Department of Integrative and Cellular Physiology, University of Nebraska Medical Center, Omaha, NE, United States
| | - Yu-long Li
- Department of Emergency Medicine, University of Nebraska Medical Center, Omaha, NE, United States
| | - Hong Zheng
- Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, United States
| | - Kaushik P. Patel
- Department of Integrative and Cellular Physiology, University of Nebraska Medical Center, Omaha, NE, United States
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Olde Hanhof CJA, Dilmen E, Yousef Yengej FA, Latta F, Ammerlaan CME, Schreurs J, Hooijmaijers L, Jansen J, Rookmaaker MB, Orhon I, Verhaar MC, Hoenderop JG. Differentiated mouse kidney tubuloids as a novel in vitro model to study collecting duct physiology. Front Cell Dev Biol 2023; 11:1086823. [PMID: 36760360 PMCID: PMC9905633 DOI: 10.3389/fcell.2023.1086823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 01/06/2023] [Indexed: 01/26/2023] Open
Abstract
Kidney tubuloids are cell models that are derived from human or mouse renal epithelial cells and show high similarities with their in vivo counterparts. Tubuloids grow polarized in 3D, allow for long-term expansion, and represent multiple segments of the nephron, as shown by their gene expression pattern. In addition, human tubuloids form tight, functional barriers and have been succesfully used for drug testing. Our knowledge of mouse tubuloids, on the other hand, is only minimal. In this study, we further characterized mouse tubuloids and differentiated them towards the collecting duct, which led to a significant upregulation of collecting duct-specific mRNAs of genes and protein expression, including the water channel AQP2 and the sodium channel ENaC. Differentiation resulted in polarized expression of collecting duct water channels AQP2 and AQP3. Also, a physiological response to desmopressin and forskolin stimulation by translocation of AQP2 to the apical membrane was demonstrated. Furthermore, amiloride-sensitive ENaC-mediated sodium uptake was shown in differentiated tubuloids using radioactive tracer sodium. This study demonstrates that mouse tubuloids can be differentiated towards the collecting duct and exhibit collecting duct-specific function. This illustrates the potential use of mouse kidney tubuloids as novel in vitro models to study (patho)physiology of kidney diseases.
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Affiliation(s)
- C. J. A. Olde Hanhof
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - E. Dilmen
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - F. A. Yousef Yengej
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences, Utrecht, Netherlands,Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, Netherlands
| | - F. Latta
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - C. M. E. Ammerlaan
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences, Utrecht, Netherlands,Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, Netherlands
| | - J. Schreurs
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - L. Hooijmaijers
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - J. Jansen
- Department of Pathology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands,Department of Pediatric Nephrology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Amalia Children’s Hospital, Nijmegen, Netherlands,Institute of Experimental Medicine and Systems Biology, Medical Faculty RWTH Aachen University, Aachen, Germany
| | - M. B. Rookmaaker
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, Netherlands
| | - I. Orhon
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - M. C. Verhaar
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, Netherlands
| | - J. G. Hoenderop
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands,*Correspondence: J. G. Hoenderop,
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Yang M, Ni L, Wang Y, Xuan Z, Wu H, Zhan W, Wan X, Wang J, Xu F. Screening bioactive compounds from Danggui-shaoyao-san for treating sodium retention in nephrotic syndrome using bio-affinity ultrafiltration. JOURNAL OF ETHNOPHARMACOLOGY 2022; 292:115171. [PMID: 35259444 DOI: 10.1016/j.jep.2022.115171] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 02/26/2022] [Accepted: 03/02/2022] [Indexed: 06/14/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Danggui-shaoyao-san (DSS), a representative formula of Traditional Chinese Medicine (TCM) for promoting blood circulation and diuresis (Huo-Xue-Li-Shui) therapy, has been used to clinically nephrotic syndrome (NS) and relieve nephrotic edema. AIM OF THE STUDY To explore the effects and mechanisms of DSS in improving sodium retention and to identify the bioactive compounds from DSS. MATERIALS AND METHODS DSS prescriptions were disassembled into Yangxue-Huoxue (YXHX) and Jianpi-Lishui (JPLS). A nephrotic rat model was induced with puromycin aminonucleoside (PAN), and the effects on urinary sodium excretion, urinary plasmin(gen) content, and plasmin activity of DSS, YXHX, and JPLS extracts were assessed. The inhibitory effects on urokinase-type plasminogen activator (uPA) and plasmin activity of extracts were evaluated in vitro. Bio-affinity ultrafiltration and high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (BAU-UPLC-Q/TOF-MS) were used to rapidly screen and qualitatively analyze the uPA/plasmin affinity compounds from DSS extract. Additionally, uPA/plasmin inhibition assays and molecular docking were used to verify the activity and affinity mechanisms of the potential bioactive compounds. RESULTS In vivo, DSS, YXHX, and JPLS prevented sodium retention in nephrotic rats. DSS and YXHX treatment decreased urinary plasmin activity but did not alter urinary plasmin(ogen) concentration, and their extracts showed strong uPA and plasmin inhibitory activity in vitro. These results suggested that uPA and plasmin are direct targets of DSS and YXHX in intervening NS sodium retention. Using BAU-UPLC-Q/TOF-MS, gallic acids, methyl gallate, albiflorin, and 1,2,3,4,6-O-pentagalloylglucose (PGG) were screened as uPA or plasmin affinity compounds. Among them, PGG was found to be a uPA and plasmin dual inhibitor, with an IC50 of 6.861 μM against uPA and an IC50 of 149.0 μM against plasmin. The molecular docking results of PGG with uPA and plasmin were consistent with the verification results. CONCLUSION Intervening in sodium retention by inhibiting uPA-mediated plasmin generation and plasmin activity in the kidneys could be possible mechanisms for DSS, as indicated by the results in PAN-induced nephrotic rats. We conclude that PGG is a potential bioactive compound responsible for the effect of DSS on natriuresis.
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Affiliation(s)
- Mo Yang
- Scientific Research & Technology Center, Anhui University of Chinese Medicine, Hefei, 230038, PR China; Key Laboratory of Xin'an Medicine, Ministry of Education, Anhui University of Chinese Medicine, Hefei, 230038, PR China.
| | - Lianghou Ni
- School of Pharmacy, Anhui University of Chinese Medicine, Hefei, 230012, PR China.
| | - Yunlai Wang
- School of Pharmacy, Anhui University of Chinese Medicine, Hefei, 230012, PR China; Anhui Province Key Laboratory of Chinese Medicinal Formula, Hefei, 230012, PR China.
| | - Zihua Xuan
- School of Pharmacy, Anhui University of Chinese Medicine, Hefei, 230012, PR China.
| | - Huan Wu
- Scientific Research & Technology Center, Anhui University of Chinese Medicine, Hefei, 230038, PR China; Key Laboratory of Xin'an Medicine, Ministry of Education, Anhui University of Chinese Medicine, Hefei, 230038, PR China; Anhui Province Key Laboratory of Chinese Medicinal Formula, Hefei, 230012, PR China.
| | - Wenjing Zhan
- School of Pharmacy, Anhui Medical University, Hefei, 230032, PR China.
| | - Xinyu Wan
- School of Integrated Chinese and Western Medicine, Anhui University of Chinese Medicine, Hefei, 230012, PR China.
| | - Jinghui Wang
- School of Integrated Chinese and Western Medicine, Anhui University of Chinese Medicine, Hefei, 230012, PR China.
| | - Fan Xu
- School of Pharmacy, Anhui University of Chinese Medicine, Hefei, 230012, PR China; Anhui Province Key Laboratory of Chinese Medicinal Formula, Hefei, 230012, PR China.
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8
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Xiao M, Bohnert BN, Grahammer F, Artunc F. Rodent models to study sodium retention in experimental nephrotic syndrome. Acta Physiol (Oxf) 2022; 235:e13844. [PMID: 35569011 DOI: 10.1111/apha.13844] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 05/02/2022] [Accepted: 05/10/2022] [Indexed: 12/12/2022]
Abstract
Sodium retention and edema are hallmarks of nephrotic syndrome (NS). Different experimental rodent models have been established for simulating NS, however, not all of them feature sodium retention which requires proteinuria to exceed a certain threshold. In rats, puromycin aminonucleoside nephrosis (PAN) is a classic NS model introduced in 1955 that was adopted as doxorubicin-induced nephropathy (DIN) in 129S1/SvImJ mice. In recent years, mice with inducible podocin deletion (Nphs2Δipod ) or podocyte apoptosis (POD-ATTAC) have been developed. In these models, sodium retention is thought to be caused by activation of the epithelial sodium channel (ENaC) in the distal nephron through aberrantly filtered serine proteases or proteasuria. Strikingly, rodent NS models follow an identical chronological time course after the development of proteinuria featuring sodium retention within days and spontaneous reversal thereafter. In DIN and Nphs2Δipod mice, inhibition of ENaC by amiloride or urinary serine protease activity by aprotinin prevents sodium retention, opening up new and promising therapeutic approaches that could be translated into the treatment of nephrotic patients. However, the essential serine protease(s) responsible for ENaC activation is (are) still unknown. With the use of nephrotic rodent models, there is the possibility that this (these) will be identified in the future. This review summarizes the various rodent models used to study experimental nephrotic syndrome and the insights gained from these models with regard to the pathophysiology of sodium retention.
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Affiliation(s)
- Mengyun Xiao
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine University Hospital Tübingen Tübingen Germany
| | - Bernhard N. Bohnert
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine University Hospital Tübingen Tübingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tübingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tübingen Germany
| | - Florian Grahammer
- III. Department of Medicine University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Ferruh Artunc
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine University Hospital Tübingen Tübingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tübingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tübingen Germany
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9
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Anand D, Hummler E, Rickman OJ. ENaC activation by proteases. Acta Physiol (Oxf) 2022; 235:e13811. [PMID: 35276025 PMCID: PMC9540061 DOI: 10.1111/apha.13811] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/04/2022] [Accepted: 03/08/2022] [Indexed: 12/13/2022]
Abstract
Proteases are fundamental for a plethora of biological processes, including signalling and tissue remodelling, and dysregulated proteolytic activity can result in pathogenesis. In this review, we focus on a subclass of membrane‐bound and soluble proteases that are defined as channel‐activating proteases (CAPs), since they induce Na+ ion transport through an autocrine mechanism when co‐expressed with the highly amiloride‐sensitive epithelial sodium channel (ENaC) in Xenopus oocytes. These experiments first identified CAP1 (channel‐activating protease 1, prostasin) followed by CAP2 (channel‐activating protease 2, TMPRSS4) and CAP3 (channel‐activating protease 3, matriptase) as in vitro mediators of ENaC current. Since then, more serine‐, cysteine‐ and metalloproteases were confirmed as in vitro CAPs that potentially cleave and regulate ENaC, and thus this nomenclature was not further followed, but is accepted as functional term or alias. The precise mechanism of ENaC modulation by proteases has not been fully elucidated. Studies in organ‐specific protease knockout models revealed evidence for their role in increasing ENaC activity, although the proteases responsible for ENaC activation are yet to be identified. We summarize recent findings in animal models of these CAPs with respect to their implication in ENaC activation. We discuss the consequences of dysregulated CAPs underlying epithelial phenotypes in pathophysiological conditions, and the role of selected protease inhibitors. We believe that these proteases may present interesting therapeutic targets for diseases with aberrant sodium homoeostasis.
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Affiliation(s)
- Deepika Anand
- Department of Biomedical Sciences University of Lausanne Lausanne Switzerland
- National Center of Competence in Research, Kidney.CH Lausanne Switzerland
| | - Edith Hummler
- Department of Biomedical Sciences University of Lausanne Lausanne Switzerland
- National Center of Competence in Research, Kidney.CH Lausanne Switzerland
| | - Olivia J. Rickman
- Department of Biomedical Sciences University of Lausanne Lausanne Switzerland
- National Center of Competence in Research, Kidney.CH Lausanne Switzerland
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10
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Essigke D, Bohnert BN, Janessa A, Wörn M, Omage K, Kalbacher H, Birkenfeld AL, Bugge TH, Szabo R, Artunc F. Sodium retention in nephrotic syndrome is independent of the activation of the membrane-anchored serine protease prostasin (CAP1/PRSS8) and its enzymatic activity. Pflugers Arch 2022; 474:613-624. [PMID: 35312839 PMCID: PMC9117342 DOI: 10.1007/s00424-022-02682-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 02/25/2022] [Accepted: 03/04/2022] [Indexed: 12/11/2022]
Abstract
Experimental nephrotic syndrome leads to activation of the epithelial sodium channel (ENaC) by proteolysis and promotes renal sodium retention. The membrane-anchored serine protease prostasin (CAP1/PRSS8) is expressed in the distal nephron and participates in proteolytic ENaC regulation by serving as a scaffold for other serine proteases. However, it is unknown whether prostasin is also involved in ENaC-mediated sodium retention of experimental nephrotic syndrome. In this study, we used genetically modified knock-in mice with Prss8 mutations abolishing its proteolytic activity (Prss8-S238A) or prostasin activation (Prss8-R44Q) to investigate the development of sodium retention in doxorubicin-induced nephrotic syndrome. Healthy Prss8-S238A and Prss8-R44Q mice had normal ENaC activity as reflected by the natriuretic response to the ENaC blocker triamterene. After doxorubicin injection, all genotypes developed similar proteinuria. In all genotypes, urinary prostasin excretion increased while renal expression was not altered. In nephrotic mice of all genotypes, triamterene response was similarly increased, consistent with ENaC activation. As a consequence, urinary sodium excretion dropped in all genotypes and mice similarly gained body weight by + 25 ± 3% in Prss8-wt, + 20 ± 2% in Prss8-S238A and + 28 ± 3% in Prss8-R44Q mice (p = 0.16). In Western blots, expression of fully cleaved α- and γ-ENaC was similarly increased in nephrotic mice of all genotypes. In conclusion, proteolytic ENaC activation and sodium retention in experimental nephrotic syndrome are independent of the activation of prostasin and its enzymatic activity and are consistent with the action of aberrantly filtered serine proteases or proteasuria.
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Affiliation(s)
- Daniel Essigke
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine, University Hospital Tübingen, Otfried-Mueller-Str.10, 72076, Tuebingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen, Tuebingen, Germany
- German Center for Diabetes Research (DZD) at the University Tübingen, Tuebingen, Germany
| | - Bernhard N Bohnert
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine, University Hospital Tübingen, Otfried-Mueller-Str.10, 72076, Tuebingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen, Tuebingen, Germany
- German Center for Diabetes Research (DZD) at the University Tübingen, Tuebingen, Germany
| | - Andrea Janessa
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine, University Hospital Tübingen, Otfried-Mueller-Str.10, 72076, Tuebingen, Germany
| | - Matthias Wörn
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine, University Hospital Tübingen, Otfried-Mueller-Str.10, 72076, Tuebingen, Germany
| | - Kingsley Omage
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine, University Hospital Tübingen, Otfried-Mueller-Str.10, 72076, Tuebingen, Germany
| | | | - Andreas L Birkenfeld
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine, University Hospital Tübingen, Otfried-Mueller-Str.10, 72076, Tuebingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen, Tuebingen, Germany
- German Center for Diabetes Research (DZD) at the University Tübingen, Tuebingen, Germany
| | - Thomas H Bugge
- Proteases and Tissue Remodeling Section, NIDCR, National Institutes of Health, Bethesda, MD, USA
| | - Roman Szabo
- Proteases and Tissue Remodeling Section, NIDCR, National Institutes of Health, Bethesda, MD, USA
| | - Ferruh Artunc
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine, University Hospital Tübingen, Otfried-Mueller-Str.10, 72076, Tuebingen, Germany.
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen, Tuebingen, Germany.
- German Center for Diabetes Research (DZD) at the University Tübingen, Tuebingen, Germany.
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11
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Artunc F, Bohnert BN, Schneider JC, Staudner T, Sure F, Ilyaskin AV, Wörn M, Essigke D, Janessa A, Nielsen NV, Birkenfeld AL, Etscheid M, Haerteis S, Korbmacher C, Kanse SM. Proteolytic activation of the epithelial sodium channel (ENaC) by factor VII activating protease (FSAP) and its relevance for sodium retention in nephrotic mice. Pflugers Arch 2021; 474:217-229. [PMID: 34870751 PMCID: PMC8766372 DOI: 10.1007/s00424-021-02639-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 10/05/2021] [Accepted: 10/18/2021] [Indexed: 12/18/2022]
Abstract
Proteolytic activation of the epithelial sodium channel (ENaC) by aberrantly filtered serine proteases is thought to contribute to renal sodium retention in nephrotic syndrome. However, the identity of the responsible proteases remains elusive. This study evaluated factor VII activating protease (FSAP) as a candidate in this context. We analyzed FSAP in the urine of patients with nephrotic syndrome and nephrotic mice and investigated its ability to activate human ENaC expressed in Xenopus laevis oocytes. Moreover, we studied sodium retention in FSAP-deficient mice (Habp2−/−) with experimental nephrotic syndrome induced by doxorubicin. In urine samples from nephrotic humans, high concentrations of FSAP were detected both as zymogen and in its active state. Recombinant serine protease domain of FSAP stimulated ENaC-mediated whole-cell currents in a time- and concentration-dependent manner. Mutating the putative prostasin cleavage site in γ-ENaC (γRKRK178AAAA) prevented channel stimulation by the serine protease domain of FSAP. In a mouse model for nephrotic syndrome, active FSAP was present in nephrotic urine of Habp2+/+ but not of Habp2−/− mice. However, Habp2−/− mice were not protected from sodium retention compared to nephrotic Habp2+/+ mice. Western blot analysis revealed that in nephrotic Habp2−/− mice, proteolytic cleavage of α- and γ-ENaC was similar to that in nephrotic Habp2+/+ animals. In conclusion, active FSAP is excreted in the urine of nephrotic patients and mice and activates ENaC in vitro involving the putative prostasin cleavage site of γ-ENaC. However, endogenous FSAP is not essential for sodium retention in nephrotic mice.
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Affiliation(s)
- Ferruh Artunc
- Department of Internal Medicine, Division of Endocrinology, Diabetology and Nephrology, University Hospital Tübingen, Tubingen, Germany. .,Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen, Tubingen, Germany. .,German Center for Diabetes Research (DZD) at the University Tübingen, Tubingen, Germany.
| | - Bernhard N Bohnert
- Department of Internal Medicine, Division of Endocrinology, Diabetology and Nephrology, University Hospital Tübingen, Tubingen, Germany.,Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen, Tubingen, Germany.,German Center for Diabetes Research (DZD) at the University Tübingen, Tubingen, Germany
| | - Jonas C Schneider
- Department of Internal Medicine, Division of Endocrinology, Diabetology and Nephrology, University Hospital Tübingen, Tubingen, Germany
| | - Tobias Staudner
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Florian Sure
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Alexandr V Ilyaskin
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Matthias Wörn
- Department of Internal Medicine, Division of Endocrinology, Diabetology and Nephrology, University Hospital Tübingen, Tubingen, Germany
| | - Daniel Essigke
- Department of Internal Medicine, Division of Endocrinology, Diabetology and Nephrology, University Hospital Tübingen, Tubingen, Germany.,Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen, Tubingen, Germany.,German Center for Diabetes Research (DZD) at the University Tübingen, Tubingen, Germany
| | - Andrea Janessa
- Department of Internal Medicine, Division of Endocrinology, Diabetology and Nephrology, University Hospital Tübingen, Tubingen, Germany
| | - Nis V Nielsen
- Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Andreas L Birkenfeld
- Department of Internal Medicine, Division of Endocrinology, Diabetology and Nephrology, University Hospital Tübingen, Tubingen, Germany.,Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen, Tubingen, Germany.,German Center for Diabetes Research (DZD) at the University Tübingen, Tubingen, Germany
| | | | - Silke Haerteis
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany.,Institute of Anatomy, University of Regensburg, Regensburg, Germany
| | - Christoph Korbmacher
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Sandip M Kanse
- Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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12
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Althaus M, Lawong RY. Proteolytic ENaC activation in health and disease-a complicated puzzle. Pflugers Arch 2021; 474:177-179. [PMID: 34799769 PMCID: PMC8766370 DOI: 10.1007/s00424-021-02644-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 11/04/2021] [Accepted: 11/09/2021] [Indexed: 11/30/2022]
Affiliation(s)
- Mike Althaus
- Institute for Functional Gene Analytics, Department of Natural Sciences, Bonn-Rhein-Sieg University of Applied Sciences, Von-Liebig-Strasse 20, 53359, Rheinbach, Germany.
| | - Rene Yufenyuy Lawong
- Institute for Functional Gene Analytics, Department of Natural Sciences, Bonn-Rhein-Sieg University of Applied Sciences, Von-Liebig-Strasse 20, 53359, Rheinbach, Germany
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