Figure 2.

BCL-2^wt lowers levels of releasable ER Ca²⁺, and nonphosphorylatable BCL-2^AAA mutants further reduces levels. (A) MEF lines stably transfected with various BCL-2 constructs were loaded with the cytosolic calcium indicator Fura-2, and pulsed with 200 nM thapsigargin (TG) in the absence of extracellular calcium. After baseline was reached, calcium was added back to a final concentration of 2 mM free [Ca²⁺]. (B) For the curves shown in (A), basal and peak cytosolic levels of calcium were measured following TG-induced release of ER stores (average of 10 experiments).