Figure 2. Knocking down STIM1 does not reduce agonist-activated TRPC5 activity.

A, representative Ca²⁺ imaging experiment (fura-5f) showing the effects of RNAi against STIM1 on endogenous SOCE evoked by store depletion with the SERCA pump inhibitor, thapsigargin (TG; 2 μm). B, bar graph showing STIM1 siRNA treatment significantly reduces (unpaired t test; P= 0.00047) endogenous SOCE in HEK293 cells. C, experiments carried out as in A; however, TRPC5 was transiently expressed in these cells (see Methods) and 200 μm carbachol was used instead of thapsigargin in order to activate TRPC5. Note also the presence of 5 μm Gd³⁺ in these experiments to inhibit endogenous SOCE. D, bar graph showing no effect (unpaired t test) of STIM1 knockdown on TRPC5-evoked Ca²⁺ entry after stimulation with carbachol. Three to four coverslips with at least 25 cells for each coverslip were carried out for each condition.