title: Bcl-2 targeted to the endoplasmic reticulum can inhibit apoptosis induced by Myc but not etoposide in Rat-1 fibroblasts.
abstract: Bcl-2 is a key inhibitor of a broad range of apoptotic pathways, yet neither the mechanism of action nor the role of Bcl-2 subcellular localization are well understood. The subcellular localization of Bcl-2 includes the mitochondrial membrane as well as the contiguous membrane of the endoplasmic reticulum and nuclear envelope. Most studies suggest that the ability of Bcl-2 to confer cell survival is dependent upon its localization to the mitochondria. In this manuscript, we show that Bcl-2 targeted to the endoplasmic reticulum can inhibit Myc-, but not etoposide-induced apoptosis in the Rat-1 fibroblast cell line. By contrast, wild type Bcl-2 can inhibit apoptosis triggered by either death agonist. We further show both Myc and etoposide trigger disruption of mitochondrial membrane potential (MMP) and induce poly-ADP ribose polymerase (PARP) cleavage, but release of calcium was not evident. Bcl-2 abrogates apoptosis at or upstream of MMP depletion showing that Bcl-2 does not have to reside at the mitochondria to prevent apoptosis. These results further elucidate the biochemical events associated with Myc- and etoposide-induced apoptosis and significantly advance our understanding of Bcl-2 function.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Ontario Cancer Institute/Princess Margaret Hospital, Canada.
authors.forename: S T
authors.initials: ST
authors.lastname: Lee
authors.forename: K P
authors.initials: KP
authors.lastname: Hoeflich
authors.forename: G W
authors.initials: GW
authors.lastname: Wasfy
authors.forename: J R
authors.initials: JR
authors.lastname: Woodgett
authors.forename: B
authors.initials: B
authors.lastname: Leber
authors.forename: D W
authors.initials: DW
authors.lastname: Andrews
authors.forename: D W
authors.initials: DW
authors.lastname: Hedley
authors.forename: L Z
authors.initials: LZ
authors.lastname: Penn
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D020169:Caspases / Q000502:physiology; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000502:physiology*; D004789:Enzyme Activation; D005047:Etoposide / Q000494:pharmacology; D007425:Intracellular Membranes / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000502:physiology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology; D051381:Rats
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D019384:Nucleic Acid Synthesis Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D005047:Etoposide; D020169:Caspases; D002118:Calcium