Figure 6. Effect of the absence of ATP in the activation of mitochondrial Ca²⁺ uptake by genistein or SB202190.

MM5 cells expressing mitochondrially targeted mutated aequorin reconstituted with coelenterazine n were permeabilized as described in the Experimental section. After permeabilization, cells were perfused for 15 min either with the usual intracellular medium containing 1 mM ATP (upper left panel) or with intracellular medium containing 1 mM ADP instead of ATP and 5 μM oligomycin (upper right panel). Then, when indicated, 3.5 μM Ca²⁺ buffers made in the corresponding intracellular medium (with or without ATP) were perfused either in the absence (Control) or in the presence of 10 μM SB202190 (SB10), 40 μM genistein or 1 μM SB202190 (SB1). The lower panel shows the mean uptake rates obtained in 3 similar experiments of each type. SB202190 activated mitochondrial Ca²⁺ uptake similarly when ATP was substituted with nothing or by the non-hydrolysable ATP analogues ATP[S] (50 μM) or (adenosine 5′-[β,γ-imido]triphosphate (AMP-PNP) (100 μM) (results not shown).