title: Comparison of the C2A domain of synaptotagmin-I and annexin-V as probes for detecting cell death.
abstract: The induction of apoptosis is frequently accompanied by the exposure of phosphatidylserine (PS) on the cell surface, which has been detected using radionuclide and fluorescently labeled derivatives of the PS-binding protein, Annexin V. The fluorescently labeled protein has been used extensively in vitro as a diagnostic reagent for detecting cell death, and radionuclide-labeled derivatives have undergone clinical trials for detecting tumor cell death in vivo following treatment. We show here that the C2A domain of Synaptotagmin-I, which had been fluorescently labeled at a single cysteine residue introduced by site-directed mutagenesis, detected the same levels of cell death as a similarly labeled Annexin-V derivative, in drug-treated murine lymphoma and human breast cancer cell lines in vitro. However, the C2A derivative showed significantly less binding to viable cells and, as a consequence, up to 4-fold more specific binding to apoptotic and necrotic cells when compared with Annexin-V. C2A offers a potential route for the development of a new generation of more specific imaging probes for the detection of tumor cell death in the clinic.
authors.affiliation: Cancer Research UK Cambridge Research Institute, Li-Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom.
authors.forename: Israt S
authors.initials: IS
authors.lastname: Alam
authors.forename: Andre A
authors.initials: AA
authors.lastname: Neves
authors.forename: Timothy H
authors.initials: TH
authors.lastname: Witney
authors.forename: Joan
authors.initials: J
authors.lastname: Boren
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Brindle
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000737:chemistry* / Q000378:metabolism; D001943:Breast Neoplasms / Q000175:diagnosis; D016923:Cell Death; D045744:Cell Line, Tumor; D005260:Female; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D008223:Lymphoma / Q000175:diagnosis; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D050863:Synaptotagmin I / Q000737:chemistry* / Q000378:metabolism
chemical_list: D017304:Annexin A5; D005456:Fluorescent Dyes; D050863:Synaptotagmin I