Fig. 1. Expression of wild-type Bcl-2 and Bcl-2 mutants with restricted subcellular location. Jurkat T-cells were stably transfected with expression constructs targeting Bcl-2 to the endoplasmic reticulum (Bcl-2/ER) or mitochondria (Bcl-2/MT), a construct lacking the transmembrane domain (Bcl-2/TM) or with wild-type Bcl-2. Confocal microscopy was performed to confirm the subcellular localization of Bcl-2 in the appropriate compartment. The pool-transfected cells were co-stained with Bcl-2 (in red) and either with the calcium ATPase SERCA for endoplasmic staining or with cytochrome c for mitochondrial staining (in green). Colocalization of the molecules is indicated by the yellow color in the merged micrographs. In Bcl-2/ER cells (A) Bcl-2 colocalizes with SERCA but not with cytochrome c. In Bcl-2/MT cells (B) Bcl-2 clearly colocalizes with cytochrome c but not with SERCA. By contrast, Bcl-2/TM (C) shows a diffuse expression pattern in the cytoplasm and nucleus. Wild-type Bcl-2 (D) is detectable in the perinuclear region, the ER and the mitochondria.