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Maharjan AS, Wyness SP, Ray JA, Willcox TL, Seiter JD, Genzen JR. Detection and characterization of estradiol (E2) and unconjugated estriol (uE3) immunoassay interference due to anti-bovine alkaline phosphatase (ALP) antibodies. Pract Lab Med 2019; 17:e00131. [PMID: 31538105 PMCID: PMC6745434 DOI: 10.1016/j.plabm.2019.e00131] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 07/17/2019] [Accepted: 08/26/2019] [Indexed: 11/15/2022] Open
Abstract
Objectives Competitive immunoenyzmatic assays for estradiol (E2) and unconjugated estriol (uE3) on UniCel DxI 800 Access immunoassay systems (Beckman Coulter) utilize bovine alkaline phosphatase (ALP) for amplification. In these assays, rare 'IND' error flags indicate that a relative light unit (RLU) raw result is past the high or low end of the calibration curve but cannot be differentiated from an instrument error or analytical interference. The present studies were conducted to establish a protocol to identify analytical interference and to characterize its mechanism when present. Design and methods Matrix and recovery studies were conducted to establish a protocol for interference identification. Spiking experiments with inactivated calf intestinal ALP were performed to determine whether interference could be blocked. Commercial anti-ALP antibodies (Abs) were spiked into human serum to model assay interference. Three E2 immunoassays which do not include ALP as a reagent component (cobas e602, Roche; Centaur XP, Siemens; ARCHITECT i2000SR, Abbott) were tested for comparative purposes. Results 1:2 dilution of specimen into Access Sample Diluent A (Beckman) differentiated IND error flags due to true low results (e.g. less than the analytical measurement range; AMR) from those due to assay interference. Interferences were reduced by pre-incubation with inactivated ALP and could be replicated by spiking with commercial anti-ALP Abs. Conclusions Patient anti-bovine ALP Abs can cause interference on DxI 800 E2 and uE3 assays. This model can be used to investigate interference risk with other ALP-dependent assays.
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Key Words
- ALP, alkaline phosphatase
- AMR, analytical measurement range
- Alkaline phosphatase
- Analytical systems
- CLIA, Clinical Laboratory Improvement Amendments
- E2, estradiol
- Endocrinology
- IND, indeterminate ‘no value’ error flag
- Immunoassay
- Interference
- MoM, multiple of the median
- PBS, phosphate buffered saline
- RLU, relative light unit
- ddH2O, demineralized distilled water
- uE3, unconjugated estriol
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Affiliation(s)
- Anu S. Maharjan
- Department of Pathology, University of Utah, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Sara P. Wyness
- ARUP Institute for Clinical and Experimental Pathology, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Julie A. Ray
- ARUP Institute for Clinical and Experimental Pathology, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Tanya L. Willcox
- ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | | | - Jonathan R. Genzen
- Department of Pathology, University of Utah, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
- ARUP Institute for Clinical and Experimental Pathology, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
- ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
- Corresponding author. University of Utah, Department of Pathology, ARUP Laboratories, 500 Chipeta Way, Mail Code 115, Salt Lake City, UT, 84108, USA.
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Decock M, El Haylani L, Stanga S, Dewachter I, Octave JN, Smith SO, Constantinescu SN, Kienlen-Campard P. Analysis by a highly sensitive split luciferase assay of the regions involved in APP dimerization and its impact on processing. FEBS Open Bio 2015; 5:763-73. [PMID: 26500837 PMCID: PMC4588712 DOI: 10.1016/j.fob.2015.09.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 08/07/2015] [Accepted: 09/01/2015] [Indexed: 12/27/2022] Open
Abstract
Amyloid precursor protein (APP) dimerizes more than its C-terminal fragments in cells. Mutations of membrane GXXXG motifs affect Aβ production but not APP dimerization. Deletion of the APP intracellular domain increases APP dimerization.
Alzheimer’s disease (AD) is a neurodegenerative disease that causes progressive loss of cognitive functions, leading to dementia. Two types of lesions are found in AD brains: neurofibrillary tangles and senile plaques. The latter are composed mainly of the β-amyloid peptide (Aβ) generated by amyloidogenic processing of the amyloid precursor protein (APP). Several studies have suggested that dimerization of APP is closely linked to Aβ production. Nevertheless, the mechanisms controlling APP dimerization and their role in APP function are not known. Here we used a new luciferase complementation assay to analyze APP dimerization and unravel the involvement of its three major domains: the ectodomain, the transmembrane domain and the intracellular domain. Our results indicate that within cells full-length APP dimerizes more than its α and β C-terminal fragments, confirming the pivotal role of the ectodomain in this process. Dimerization of the APP transmembrane (TM) domain has been reported to regulate processing at the γ-cleavage site. We show that both non-familial and familial AD mutations in the TM GXXXG motifs strongly modulate Aβ production, but do not consistently change dimerization of the C-terminal fragments. Finally, we found for the first time that removal of intracellular domain strongly increases APP dimerization. Increased APP dimerization is linked to increased non-amyloidogenic processing.
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Key Words
- AD, Alzheimer’s disease
- AICD, APP intracellular domain
- APP
- APP, amyloid precursor protein
- Alzheimer disease
- Amyloid beta peptide
- Aβ, β-amyloid peptide
- CHO, chinese hamster ovary
- CTF, C-terminal fragment
- DAPT, N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester
- DTT, dithiothreitol
- Dimerization
- ECL, enzymatic chemi-luminescence
- ECLIA, electro-chemiluminescence immuno-assay
- FBS, fetal bovine serum
- FRET, fluorescence resonance energy transfer
- GXXXG motifs
- KPI, Kunitz-type protease inhibitor
- NSAIDs, nonsteroidal anti-inflammatory drugs
- PBS, phosphate buffered saline
- PS1/PS2, presenilin1/presenilin2
- RLU, relative light unit
- SP, signal peptide
- Split luciferase
- TM, transmembrane
- YFP, yellow fluorescent protein
- sAPPα, soluble APPα
- sAPPβ, soluble APPβ
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Affiliation(s)
- Marie Decock
- Institute of Neuroscience, Université catholique de Louvain, Brussels 1200, Belgium
| | - Laetitia El Haylani
- Institute of Neuroscience, Université catholique de Louvain, Brussels 1200, Belgium
| | - Serena Stanga
- Institute of Neuroscience, Université catholique de Louvain, Brussels 1200, Belgium
| | - Ilse Dewachter
- Institute of Neuroscience, Université catholique de Louvain, Brussels 1200, Belgium
| | - Jean-Noël Octave
- Institute of Neuroscience, Université catholique de Louvain, Brussels 1200, Belgium
| | - Steven O Smith
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
| | - Stefan N Constantinescu
- de Duve Institute and Ludwig Institute for Cancer Research, Université catholique de Louvain, Brussels 1200, Belgium
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