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Deprez L, Piggott C, van der Hagen EAE, Frasa M, Benton SC. Comparison and commutability study among four faecal immunochemical tests (FIT) systems. Clin Chem Lab Med 2024; 62:50-59. [PMID: 37327361 DOI: 10.1515/cclm-2023-0278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 06/09/2023] [Indexed: 06/18/2023]
Abstract
OBJECTIVES Faecal immunochemical tests for haemoglobin (FIT) are used in colorectal cancer screening programs around the world and increasingly for triage of symptomatic patients. FIT results are currently not traceable to a common reference standard and results obtained on various FIT systems may not be equivalent. The size of the bias between the systems is difficult to quantify due to the complex pre-analytical aspects of FIT. METHODS This study aimed to quantify the bias and the correlation between four FIT systems by measuring a panel of 38 faecal samples while limiting the effect of the pre-analytical aspects. In addition, the commutability of seven candidate reference materials (RM) was assessed. RESULTS Pairwise method comparisons based on faecal samples demonstrated Pearson correlation coefficients ranging between 0.944 and 0.970 and an average proportional bias of -30 to -35 % for one FIT system compared to the other three. The relative standard deviation among biases of the individual samples was around 20 %. Due to these sample specific differences, no decisive conclusions could be drawn in the commutability study. However, two candidate RMs, prepared in the FIT system-specific storage/extraction buffers, had a better commutable profile than the other five. CONCLUSIONS The use of a common threshold for all FIT systems is currently not possible due to the presence of a proportional bias. We have identified potential commutable RMs to take to further studies on the production of a common calibrator, with the aim being to reduce the analytical bias observed on different FIT systems.
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Affiliation(s)
- Liesbet Deprez
- European Commission, Joint Research Centre (JRC), Geel, Belgium
| | - Carolyn Piggott
- NHS Bowel Cancer Screening Programme, South of England Hub, Guildford, UK
| | - Eline A E van der Hagen
- Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, The Netherlands
- Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), Nijmegen, The Netherlands
| | - Marieke Frasa
- Department of Clinical Chemistry, Reinier Haga Medical Diagnostic Center, Delft, The Netherlands
| | - Sally C Benton
- NHS Bowel Cancer Screening Programme, South of England Hub, Guildford, UK
- Clinical Biochemistry, Royal Surrey Foundation Trust, Berkshire and Surrey Pathology Services, Guildford, UK
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Kootstra-Ros JE, van der Hagen EAE, van Schrojenstein Lantman M, Thelen M, van Berkel M. (In)direct chloride ISE measurements, room for improvement. Clin Chem Lab Med 2022; 60:e168-e171. [PMID: 35512217 DOI: 10.1515/cclm-2022-0220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/13/2022] [Indexed: 11/15/2022]
Affiliation(s)
- Jenny E Kootstra-Ros
- Department of Laboratory Medicine, University Medical Center Groningen, Groningen, The Netherlands
| | | | | | - Marc Thelen
- Department of Laboratory Medicine, Radboud University Hospital, Nijmegen, The Netherlands.,SKML, Nijmegen, The Netherlands
| | - Miranda van Berkel
- Department of Laboratory Medicine, Radboud University Hospital, Nijmegen, The Netherlands
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van der Hagen EAE, Leppink S, Bokkers K, Siebelder C, Weykamp CW. Evaluation of the ARKRAY HA-8190V instrument for HbA 1c. Clin Chem Lab Med 2020; 59:965-970. [PMID: 33554536 DOI: 10.1515/cclm-2020-1300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 12/11/2020] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Hemoglobin A1c (HbA1c) is a valuable parameter in the monitoring of diabetic patients and increasingly in diagnosis of diabetes. Manufacturers continuously optimize instruments, currently the main focus is to achieve faster turnaround times. It is important that performance specifications remain of high enough standard, which is evaluated in this study for the new ARKRAY HA-8190V instrument. METHODS The Clinical and Laboratory Standards Institute (CLSI) protocols EP-5, EP-9 and EP-10 were applied to investigate imprecision, bias and linearity. In addition potential interferences, performance in External Quality Assessment (EQA) and performance against the HA-8180V instrument in 220 clinical samples was evaluated. RESULTS The HA-8190V demonstrates a CV of ≤0.8% in IFCC SI units (≤0.6% National Glycohemoglobin Standardization Program [NGSP]) at 34 and 102 mmol/mol levels (5.3 and 11.5% NGSP) and a bias of -0.1 mmol/mol (-0.01% NGSP) at a concentration of 50 mmol/mol (6.7% NGSP), but with a significant slope as compared to target values. This results in a bias of -1.0 and 0.9 mmol/mol (-2.0 and 0.9% NGSP) at the 30 and 70 mmol/mol (4.9 and 8.6% NGSP) concentration level. Simulation of participation in the IFCC certification programme results in a Silver score (bias -0.1 mmol/mol, CV 1.1%). Interference in the presence of the most important Hb variants (AS, AC, AE, AD) and elevated HbA2 and HbF concentrations is less than 3 mmol/mol (0.3% NGSP) at a concentration of 50 mmol/mol (6.7% NGSP). CONCLUSIONS Analytical performance of the HA-8190V is very good, especially with respect to precision and HbA1c quantification in the presence of the most common Hb variants.
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Affiliation(s)
- Eline A E van der Hagen
- European Reference Laboratory for Glycohemoglobin, Queen Beatrix Hospital, Winterswijk, The Netherlands.,Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, The Netherlands
| | - Sanne Leppink
- Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, The Netherlands
| | - Karin Bokkers
- Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, The Netherlands
| | - Carla Siebelder
- European Reference Laboratory for Glycohemoglobin, Queen Beatrix Hospital, Winterswijk, The Netherlands.,Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, The Netherlands
| | - Cas W Weykamp
- European Reference Laboratory for Glycohemoglobin, Queen Beatrix Hospital, Winterswijk, The Netherlands.,Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, The Netherlands
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van der Hagen EAE, Cobbaert CM, Meijer R, Thelen MHM. Fast 0/1-h algorithm for detection of NSTEMI: are current high-sensitivity cardiac troponin assays fit for purpose? An EQA-based evaluation. Clin Chem Lab Med 2020; 57:1999-2007. [PMID: 31326959 DOI: 10.1515/cclm-2019-0253] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 06/20/2019] [Indexed: 02/06/2023]
Abstract
Background High-sensitivity cardiac troponin T/I (hs-cTnT/I) assays have improved analytical sensitivity for the detection of myocardial infarction (MI). To gain clinical specificity and sensitivity, interpretation of changes in cTn concentrations over time is crucial. The 2015 ESC NSTEMI guideline defines absolute delta values as additional rule-in and rule-out criteria for MI. A critical assumption for application of this rule is that total analytical imprecision within the delta period, including inter-instrument bias, is comparable to analytical imprecision in the validation studies. Methods Data from the Dutch External Quality Assessment Scheme (EQAS) were used to calculate inter-instrument bias and estimate imprecision for the measuring range where the proposed delta values are relevant: for Roche Elecsys hs-cTnT, 5-52 and 5-12 ng/L; for Abbott Architect hs-cTnI, 2-52 and 2-5 ng/L for rule-in and rule-out, respectively. Results For Elecsys, the median inter-instrument bias is 0.3 ng/L (n = 33 laboratories), resulting in reference change values (RCVs) of 3.0 and 1.7 ng/L, respectively, for rule-in and rule-out with imprecision as claimed by the manufacturer. With RCVs smaller than the guideline's delta thresholds, 100% of the laboratories have adequate specifications. RCVs for rule-in/rule-out increased to 4.6 ng/L/2.5 ng/L, respectively, with individual imprecisions as estimated from EQA data, resulting in 64% and 82% of laboratories with adequate specifications. For Architect, 40% of instruments (n = 10) might falsely qualify the result as clinically relevant; hence, inter-instrument bias could not be determined. Conclusions We advise laboratories that use the fast 0/1-h algorithm to introduce stringent internal quality procedures at the relevant/low concentration level, especially when multiple analyzers are randomly used.
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Affiliation(s)
- Eline A E van der Hagen
- Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), Nijmegen, The Netherlands.,Department of Clinical Chemistry, Queen Beatrix Hospital, Beatrixpark 1, 7101 BN Winterswijk, The Netherlands, Phone: +31 543544774
| | - Christa M Cobbaert
- Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Center, Leiden, The Netherlands
| | - Ron Meijer
- Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), Nijmegen, The Netherlands
| | - Marc H M Thelen
- Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), Nijmegen, The Netherlands.,Department of Clinical Chemistry and Haematology, Amphia Hospital, Breda, The Netherlands
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van der Hagen EAE, Weykamp C, Sandberg S, Stavelin AV, MacKenzie F, Miller WG. Feasibility for aggregation of commutable external quality assessment results to evaluate metrological traceability and agreement among results. Clin Chem Lab Med 2020; 59:117-125. [PMID: 32759402 DOI: 10.1515/cclm-2020-0736] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 07/22/2020] [Indexed: 11/15/2022]
Abstract
Objectives External quality assessment (EQA) with commutable samples is used for assessing agreement of results for patients' samples. We investigated the feasibility to aggregate results from four different EQA schemes to determine the bias between different measurement procedures and a reference target value. Methods We aggregated EQA results for creatinine from programs that used commutable EQA material by calculating the relative difference between individual participant results and the reference target value for each sample. The means and standard errors of the means were calculated for the relative differences. Results were partitioned by methods, manufacturers and instrument platforms to evaluate the biases for the measurement procedures. Results Data aggregated for enzymatic methods had biases that varied from -8.2 to 3.8% among seven instrument platforms for creatinine at normal concentrations (61-85 μmol/L). EQA schemes differed in the evidence provided about the commutability of their samples, and in the amount of detail collected from participants regarding the measurement procedures which limited the ability to sub-divide aggregated data by instrument platforms and models. Conclusions EQA data could be aggregated from four different programs using different commutable samples to determine bias among different measurement procedures. Criteria for commutability for EQA samples as well as standardization of reporting the measurement methods, reagents, instrument platforms and models used by participants are needed to improve the ability to aggregate the results for optimal assessment of performance of measurement procedures. Aggregating data from a larger number of EQA schemes is feasible to assess trueness on a global scale.
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Affiliation(s)
- Eline A E van der Hagen
- Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), Nijmegen, The Netherlands.,Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, The Netherlands
| | - Cas Weykamp
- Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), Nijmegen, The Netherlands.,Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, The Netherlands
| | - Sverre Sandberg
- The Norwegian Organisation for Quality Improvement of Laboratory Examinations (Noklus), Haraldsplass Deaconess Hospital, Noklus, Bergen, Norway
| | - Anne V Stavelin
- The Norwegian Organisation for Quality Improvement of Laboratory Examinations (Noklus), Haraldsplass Deaconess Hospital, Noklus, Bergen, Norway
| | - Finlay MacKenzie
- Birmingham Quality/UK NEQAS, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
| | - W Greg Miller
- Department of Pathology, Virginia Commonwealth University, Richmond, VA, USA
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van der Hagen EAE, Fokkert MJ, Kleefman AMD, Thelen MHM, van den Berg SAA, Slingerland RJ. Technical and clinical validation of the Greiner FC-Mix glycaemia tube. Clin Chem Lab Med 2017; 55:1530-1536. [PMID: 28284032 DOI: 10.1515/cclm-2016-0944] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 01/30/2017] [Indexed: 12/19/2022]
Abstract
BACKGROUND Measurement of adequate glucose concentrations is complicated by in vitro breakdown of glucose due to glycolysis. Unlike the commonly used NaF-EDTA and NaF-oxalate phlebotomy tubes, citrated NaF-EDTA tubes are reported to directly and thereby completely inhibit glycolysis. Recently, Greiner introduced the Vacuette® FC-Mix NaF-EDTA-citrate tube, currently the only NaF-citrate tube without volume-disturbing liquid additions available on the European market. Here we present its potential as alternative for the laborious and therefore unfeasible conditions for glucose sampling as recommended by the World Health Organization (WHO). METHODS The FC-Mix tube was tested against the WHO recommended method of optimal laboratory conditions, both in healthy volunteers and pregnant woman undergoing oral glucose tolerance test (oGTT) for screening of gestational diabetes mellitus (GDM). Glucose concentrations were measured after different incubation times (0-48 h) and temperatures (room temperature, 37 °C), both in uncentrifuged whole blood and centrifuged material. RESULTS Deming regression analysis shows that glucose concentrations measured in the FC-Mix tube correlate to the WHO recommended method. Stability is maintained at room temperature for 48 h and at least 24 h at 37 °C. The use of the FC-Mix tube was also validated in screening for GDM and proved comparable to the WHO recommended method in diagnostic outcome. CONCLUSIONS The new Greiner FC-Mix tube combines the easy handling of a routine tube with dry additive with the ability to immediately inhibit glycolysis as in the WHO method for optimal pre-analytical and analytical conditions and performs equally to those conditions when screening for GDM.
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van der Hagen EAE, van Loon EPM, Verkaart S, Latta F, Bindels RJM, Hoenderop JGJ. The Na+/Ca2+ Exchanger 1 (NCX1) Variant 3 as the Major Extrusion System in Renal Distal Tubular Transcellular Ca2+-Transport. Nephron Clin Pract 2015; 131:145-52. [PMID: 26418956 DOI: 10.1159/000440655] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 08/24/2015] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Fine-tuning of renal calcium (Ca(2+)) reabsorption takes place in the late distal convoluted and connecting tubules (DCT2/CNT) of the kidney via transcellular Ca(2+) transport. Here, Ca(2+) enters the cell at the apical side via the epithelial Ca(2+) channel transient receptor potential vanilloid 5 and is subsequently extruded at the basolateral side by the concerted actions of the plasma membrane Ca(2+) ATPases and the Na(+)/Ca(2+) exchanger 1 (NCX1). NCX1 is responsible for ∼ 70% of basolateral Ca(2+) extrusion. The aim of this study was to determine the predominant NCX1 variant in the kidney and its role in Ca(2+) transport. METHODS DCT2/CNT specific tubules were used to show the abundance of NCX1 specific isoforms. Renal NCX1 variants were cloned from mouse kidney tissue. Human Embryonic Kidney 293(T) cells were transiently transfected with NCX1.3, and Fura-2 measurements and 45Ca(2+) uptake assays were performed to determine several characteristics of NCX1.3 in the reverse mode. RESULTS NCX1.3 was demonstrated to be the predominant NCX1 variant in the DCT2/CNT, next to NCX1.2 and NCX1.7. NCX1.3 could be inhibited by SN-6, an NCX-specific inhibitor, whereas stimulation of the cAMP/PKA or PKC-mediated pathway did not affect Ca(2+) influx as measured in the reverse mode. Lowering intracellular Ca(2+) concentrations resulted in a decreased Ca(2+) uptake. CONCLUSION NCX1.3 is the predominant NCX variant in the DCT2/CNT tubules. Its function is dependent on intracellular Ca(2+) concentrations.
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Affiliation(s)
- Eline A E van der Hagen
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
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8
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van Loon EPM, Pulskens WP, van der Hagen EAE, Lavrijsen M, Vervloet MG, van Goor H, Bindels RJM, Hoenderop JGJ. Shedding of klotho by ADAMs in the kidney. Am J Physiol Renal Physiol 2015; 309:F359-68. [PMID: 26155844 DOI: 10.1152/ajprenal.00240.2014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 07/01/2015] [Indexed: 11/22/2022] Open
Abstract
The anti-aging gene klotho plays an important role in Ca(2+) and phosphate homeostasis. Membrane-bound klotho is an essential coreceptor for fibroblast growth factor-23 and can be cleaved by proteases, including a disintegrin and metalloproteinase (ADAM)10 and ADAM17. Cleavage of klotho occurs at a site directly above the plasma membrane (α-cut) or between the KL1 and KL2 domain (β-cut), resulting in soluble full-length klotho or KL1 and KL2 fragments, respectively. The aim of the present study was to gain insights into the mechanisms behind klotho cleavage processes in the kidney. Klotho shedding was demonstrated using a Madin-Darby canine kidney cell line stably expressing klotho and human embryonic kidney-293 cells transiently transfected with klotho. Here, we report klotho expression on both the basolateral and apical membrane, with a higher abundance of klotho at the apical membrane and in the apical media. mRNA expression of ADAM17 and klotho were enriched in mouse distal convoluted and connecting tubules. In vitro ADAM/matrix metalloproteinase inhibition by TNF484 resulted in a concentration-dependent inhibition of the α-cut, with a less specific effect on β-cut shedding. In vivo TNF484 treatment in wild-type mice did not change urinary klotho levels. However, ADAM/matrix metalloproteinase inhibition did increase renal and duodenal mRNA expression of phosphate transporters, whereas serum phosphate levels were significantly decreased. In conclusion, our data show that renal cells preferentially secrete klotho to the apical side and suggest that ADAMs are responsible for α-cut cleavage.
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Affiliation(s)
- Ellen P M van Loon
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Wilco P Pulskens
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Eline A E van der Hagen
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Marla Lavrijsen
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Marc G Vervloet
- Department of Nephrology, VU University Medical Center, Amsterdam, The Netherlands; and
| | - Harry van Goor
- Department of Pathology and Medical Biology, University Medical Center Groningen, Groningen, The Netherlands
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joost G J Hoenderop
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands;
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van der Hagen EAE, Tudpor K, Verkaart S, Lavrijsen M, van der Kemp A, van Zeeland F, Bindels RJM, Hoenderop JGJ. β1-Adrenergic receptor signaling activates the epithelial calcium channel, transient receptor potential vanilloid type 5 (TRPV5), via the protein kinase A pathway. J Biol Chem 2014; 289:18489-96. [PMID: 24828496 DOI: 10.1074/jbc.m113.491274] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Epinephrine and norepinephrine are present in the pro-urine. β-Adrenergic receptor (β-AR) blockers administered to counteract sympathetic overstimulation in patients with congestive heart failure have a negative inotropic effect, resulting in reduced cardiac contractility. Positive inotropes, β1-AR agonists, are used to improve cardiac functions. Active Ca(2+) reabsorption in the late distal convoluted and connecting tubules (DCT2/CNT) is initiated by Ca(2+) influx through the transient receptor potential vanilloid type 5 (TRPV5) Ca(2+) channel. Although it was reported that β-ARs are present in the DCT2/CNT region, their role in active Ca(2+) reabsorption remains elusive. Here we revealed that β1-AR, but not β2-AR, is localized with TRPV5 in DCT2/CNT. Subsequently, treatment of TRPV5-expressing mouse DCT2/CNT primary cell cultures with the β1-AR agonist dobutamine showed enhanced apical-to-basolateral transepithelial Ca(2+) transport. In human embryonic kidney (HEK293) cells, dobutamine was shown to stimulate cAMP production, signifying functional β1-AR expression. Fura-2 experiments demonstrated increased activity of TRPV5 in response to dobutamine, which could be prevented by the PKA inhibitor H89. Moreover, nonphosphorylable T709A-TRPV5 and phosphorylation-mimicking T709D-TRPV5 mutants were unresponsive to dobutamine. Surface biotinylation showed that dobutamine did not affect plasma membrane abundance of TRPV5. In conclusion, activation of β1-AR stimulates active Ca(2+) reabsorption in DCT2/CNT; an increase in TRPV5 activity via PKA phosphorylation of residue Thr-709 possibly plays an important role. These data explicate a calciotropic role in addition to the inotropic property of β1-AR.
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Affiliation(s)
- Eline A E van der Hagen
- From the Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - Kukiat Tudpor
- From the Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - Sjoerd Verkaart
- From the Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - Marla Lavrijsen
- From the Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - Annemiete van der Kemp
- From the Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - Femke van Zeeland
- From the Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - René J M Bindels
- From the Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - Joost G J Hoenderop
- From the Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
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de Groot T, van der Hagen EAE, Verkaart S, te Boekhorst VAM, Bindels RJM, Hoenderop JGJ. Role of the transient receptor potential vanilloid 5 (TRPV5) protein N terminus in channel activity, tetramerization, and trafficking. J Biol Chem 2011; 286:32132-9. [PMID: 21795703 DOI: 10.1074/jbc.m111.226878] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The epithelial Ca(2+) channel transient receptor potential vanilloid 5 (TRPV5) constitutes the apical entry site for active Ca(2+) reabsorption in the kidney. The TRPV5 channel is a member of the TRP family of cation channels, which are composed of four subunits together forming a central pore. Regulation of channel activity is tightly controlled by the intracellular N and C termini. The TRPV5 C terminus regulates channel activity by various mechanisms, but knowledge regarding the role of the N terminus remains scarce. To study the role of the N terminus in TRPV5 regulation, we generated different N-terminal deletion constructs. We found that deletion of the first 32 residues did not affect TRPV5-mediated (45)Ca(2+) uptake, whereas deletion up to residue 34 and 75 abolished channel function. Immunocytochemistry demonstrated that these mutant channels were retained in the endoplasmic reticulum and in contrast to wild-type TRPV5 did not reach the Golgi apparatus, explaining the lack of complex glycosylation of the mutants. A limited amount of mutant channels escaped the endoplasmic reticulum and reached the plasma membrane, as shown by cell surface biotinylation. These channels did not internalize, explaining the reduced but significant amount of these mutant channels at the plasma membrane. Wild-type TRPV5 channels, despite significant plasma membrane internalization, showed higher plasma membrane levels compared with the mutant channels. The assembly into tetramers was not affected by the N-terminal deletions. Thus, the N-terminal residues 34-75 are critical in the formation of a functional TRPV5 channel because the deletion mutants were present at the plasma membrane as tetramers, but lacked channel activity.
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Affiliation(s)
- Theun de Groot
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands
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