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Korbakis D, Brinc D, Schiza C, Soosaipillai A, Jarvi K, Drabovich AP, Diamandis EP. Immunocapture-Selected Reaction Monitoring Screening Facilitates the Development of ELISA for the Measurement of Native TEX101 in Biological Fluids. Mol Cell Proteomics 2015; 14:1517-26. [PMID: 25813379 DOI: 10.1074/mcp.m114.047571] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Indexed: 11/06/2022] Open
Abstract
Monoclonal antibodies that bind the native conformation of proteins are indispensable reagents for the development of immunoassays, production of therapeutic antibodies and delineating protein interaction networks by affinity purification-mass spectrometry. Antibodies generated against short peptides, protein fragments, or even full length recombinant proteins may not bind the native protein form in biological fluids, thus limiting their utility. Here, we report the application of immunocapture coupled with selected reaction monitoring measurements (immunocapture-SRM), in the rapid screening of hybridoma culture supernatants for monoclonal antibodies that bind the native protein conformation. We produced mouse monoclonal antibodies, which detect in human serum or seminal plasma the native form of the human testis-expressed sequence 101 (TEX101) protein-a recently proposed biomarker of male infertility. Pairing of two monoclonal antibodies against unique TEX101 epitopes led to the development of an ELISA for the measurement of TEX101 in seminal plasma (limit of detection: 20 pg/ml) and serum (limit of detection: 40 pg/ml). Measurements of matched seminal plasma samples, obtained from men pre- and post-vasectomy, confirmed the absolute diagnostic specificity and sensitivity of TEX101 for noninvasive identification of physical obstructions in the male reproductive tract. Measurement of male and female serum samples revealed undetectable levels of TEX101 in the systemic circulation of healthy individuals. Immunocapture-SRM screening may facilitate development of monoclonal antibodies and immunoassays against native forms of challenging protein targets.
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Affiliation(s)
- Dimitrios Korbakis
- From the ‡Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada; §Department of Clinical Biochemistry, University Health Network, Toronto, Canada
| | - Davor Brinc
- ¶Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Canada
| | - Christina Schiza
- From the ‡Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada; ¶Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Canada
| | | | - Keith Jarvi
- ‖Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada; **Department of Surgery, Division of Urology, Mount Sinai Hospital, University of Toronto, Canada
| | - Andrei P Drabovich
- From the ‡Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada; §Department of Clinical Biochemistry, University Health Network, Toronto, Canada;
| | - Eleftherios P Diamandis
- From the ‡Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada; §Department of Clinical Biochemistry, University Health Network, Toronto, Canada; ¶Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Canada; ‖Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada;
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Robert JC, Benkouka F, Bayle D, Hervatin F, Soumarmon A. H+/K(+)-ATPase contents of human, rabbit, hog and rat gastric mucosa. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1024:167-72. [PMID: 2159803 DOI: 10.1016/0005-2736(90)90220-i] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A monoclonal antibody (mAb 95-111) was used to titrate the amounts of H+/K(+)-ATPase in subcellular fractions of the fundus of rats, pigs, rabbits and humans. All four had similar amounts of H+/K(+)-ATPase: 2.1 +/- 0.5 (human), 1.9 +/- 0.4 (rabbit), 4.4 +/- 0.5 (rat) and 4.2 +/- 0.8 (hog) mg ATPase/g wet tissue. The antigen concentrations and H+/K(+)-ATPase enzymatic activities of subcellular fractions were linearly correlated in all species but rat suggesting that human, rabbit and hog H+/K(+)-ATPases have similar rates of catalysis (223 mumol Pi/h per mg ATPase). The non-correlation of rat data probably reflects the known lability of the rat enzyme. Hence, immuno-titration promises to be a more reliable method of estimating rat ATPase than the currently used enzymatic assay. The H+/K(+)-ATPase content of human biopsies was 20-fold higher than previously-published (Smolka, A. and Weinstein, W.M. (1986) Gastroenterology 90, 532-539) suggesting that the previous immuno-titration underestimated the H+/K(+)-ATPase content of the human fundus.
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Affiliation(s)
- J C Robert
- INSERM Unité 10, Ancien Hôpital Bichat, Paris, France
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Thornton DJ, Sheehan JK, Nieduszynski IA. A study of the interaction between cartilage proteoglycan and link protein. Biochem J 1987; 248:943-51. [PMID: 3435493 PMCID: PMC1148641 DOI: 10.1042/bj2480943] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The interaction between proteoglycan and link protein extracted from bovine articular cartilage (15-18-month-old animals) was investigated in 0.5 M-guanidinium chloride. The proteoglycans, radiolabelled as the aggregate (A1 fraction), were fractionated by two 'dissociative' density-gradient centrifugations (A1D1D1) followed by a rate-zonal centrifugation (S1) to yield an A1D1D1S1 preparation. At least 65% of these proteoglycans were able to bind to hyaluronate, but only 52% were able to bind to link protein as assessed by chromatography on Sepharose CL-2B. Over 80% of the [3H]link-protein preparation, radiolabelled as the aggregate, was able to interact with proteoglycan as assessed by chromatography on Sepharose CL-4B. Equilibrium-boundary-centrifugation studies performed at low link-protein concentrations (2.42 x 10(-9) M-5.93 x 10(-8) M) were analysed by Scatchard-type plots and indicated a Kd of 1.5 x 10(-8) M and a stoichiometry, n = 0.56, i.e. approx. 56% of those proteoglycans capable of binding to link protein had a strong site for link protein if a 1:1 stoichiometry were assumed. However, experiments performed at higher link-protein concentrations (3.5 x 10(-7) M and 8 x 10(-7) M) yielded stoichiometry values which were link-protein-concentration-dependent. Non-equilibrium binding studies using chromatography on Sepharose CL-2B and rate-zonal centrifugation yielded apparent stoichiometries between 0.6 and 7.5 link-protein molecules per proteoglycan monomer as a function of increasing link-protein concentration. It was concluded that a proportion of the proteoglycan molecules had a strong site for binding a single link protein (Kd 1.5 x 10(-8) M) and that at high link-protein concentrations a weaker, open-ended, process of link-protein self-association nucleated upon the strong link-protein-proteoglycan complex occurred. Hyaluronate oligosaccharides appeared to abolish a proportion of this self-association (as observed by Bonnet, Dunham & Hardingham [(1985) Biochem. J. 228, 77-85] in a study of link-protein-hyaluronate-oligosaccharide interactions) so as to leave a link protein:proteoglycan stoichiometry of 2. It is not clear whether this second link-protein molecule binds directly to the proteoglycan or to the first link protein.
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Affiliation(s)
- D J Thornton
- Department of Biological Sciences, University of Lancaster, Bailrigg, U.K
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