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Updated: Aug 13, 2026

Detection of Toxin Translocation into the Host Cytosol by Surface Plasmon Resonance
Published on: January 3, 2012
Cholera toxin and its B subunit do not change cytosolic free calcium concentration
E I Astashkin1, A M Surin, M G Mikhna
1All-Union Research Institute of Biotechnology, Moscow, USSR.
Abstract:
Using the fluorescent Ca2+ probe Quin-2 it has been reported that cholera toxin (CT) and its B subunit (B-CT) increase cytosolic free Ca2+ concentration ([Ca2+]i) in entherocytes, thymocytes and fibroblasts. In this work we show, however, that the fluorescence increases of Quin-2-loaded cells (rat thymocytes, mouse splenocytes, P-388 macrophages and 3T3 fibroblasts) observed upon addition of CT or B-CT are not caused by an increase in [Ca2+]i. The observed effect appears to be accounted for by EDTA-2Na admixtures (present as conservation agent in all CT and B-CT preparations) which 'unquenches' the fluorescence of Quin-2 acid leaked out from the cells into the extracellular medium and produces influorescent complexes with contaminating heavy metal ions. Thus the mitogenic effect of B-CT is not obviously connected with the cytosolic free Ca2+ increase but is probably due to ganglioside-mediated protein phosphorylation.
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