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Figure 4 | BMC Cancer

Figure 4

From: Carnosine inhibits carbonic anhydrase IX-mediated extracellular acidosis and suppresses growth of HeLa tumor xenografts

Figure 4

Carnosine impairs binding of CA IX-specific inhibitor and antibodies and affects formation of a CA IX metabolon. (A) Immunofluorescence signal of FITC-labeled CA specific inhibitor, which binds only to hypoxic cells with catalytically active CA IX, was markedly reduced after treatment of HeLa cells with 20 mM carnosine in hypoxia for 48 h. (B) Graph of competitive inhibition ELISA showing the percentage of inhibition after cultivation of HeLa cells with different concentrations of carnosine together with specific CA IX antibodies MAb10 and MAb12. Binding of antibodies to conformational epitopes in the catalytic domain of CA IX was inhibited by carnosine in a concentration-dependent manner. (C) SiHa cells cultured in islands under hypoxic conditions were analyzed by proximity ligation assay to visualize direct interaction between CA IX and the anion exchanger AE2 in the functional metabolon. The positive signal represented by bright white dots was considerably reduced in cells treated with 20 mM carnosine for 24 h, supporting the proposal that binding of carnosine alters the conformation of CA IX. Scale bar, 20 μm.

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