Abstract 1436: Determination of antibody's specificity towards phosphorylated protein targets with automated in-capillary enzyme treatment and immunoassay

Abstract

Protein phosphorylation is a reversible reaction that is integral in numerous signaling cascades. Characterization of signaling cascades has been largely detected by immunoblotting with phospho-specific antibodies, which may or may not have enough specificity or affinity. Currently, a separate lysate without any phosphatase inhibitors or a separate blot is needed to determine an antibody's specificity. Here we describe a simple assay that leverages automation and quantitation with capillary electrophoresis-based immunoassay (CEIA) to assess the specificity of these antibodies with a single lysate preparation. In this study, three lysate models are used: K562 ± TNFα treatment, 50 ng/mL phorbol myristate acetate (PMA) differentiated THP-1 ± 1 μg/mL lipopolysaccharide (LPS) treatment, and cytotoxic T lymphocytes (CTL) ± 10 ng/mL PMA and 500 ng/mL ionomycin treatment. K562 cell lysates are commercially purchased whereas THP-1 lysates are generated in-house. For CTL cells, whole blood cells from a single donor are isolated and expanded with commercially available kits. Expanded CTL cells are then stimulated with PMA and ionomycin for 15 minutes. Untreated and treated lysate samples are separated and captured to the inner lumen of the capillary wall with UV activated crosslink chemistry. Cross-linked proteins are treated with lambda phosphatase for 1 hour followed by the immunoassay to investigate the specificity of antibodies against phosphorylated protein targets respective to each activated pathway using either chemiluminescent or fluorescent detection. Preliminary data suggest phospho-specific signal decreased >90% with no significant changes to the non-specific noise. The method described here eliminates the need for multiple lysate preparations or an additional blot to assess an antibody's specificity to a phosphorylated protein target. Citation Format: Daryl A. Taketa, Rainer Grant, Tufan Aydogdu. Determination of antibody's specificity towards phosphorylated protein targets with automated in-capillary enzyme treatment and immunoassay [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1436.