Regulation of apoptosis by endoplasmic reticulum pathways.
Apoptotic programmed cell death pathways are activated by a diverse array of cell extrinsic and intrinsic signals, most of which are ultimately coupled to the activation of effector caspases. In many instances, this involves an obligate propagation through mitochondria, causing egress of critical proapoptotic regulators to the cytosol. Central to the regulation of the mitochondrial checkpoint is a complex three-way interplay between members of the BCL-2 family, which are comprised of an antiapoptotic subgroup including BCL-2 itself, and the proapoptotic BAX,BAK and BH3-domain-only subgroups. Constituents of all three of these BCL-2 classes, however, also converge on the endoplasmic reticulum (ER), an organelle whose critical contributions to apoptosis is only now becoming apparent. In addition to propagating death-inducing stress signals itself, the ER also contributes in a fundamental way to Fas-mediated apoptosis and to p53-dependent pathways resulting from DNA damage and oncogene expression. Mobilization of ER calcium stores can initiate the activation of cytoplasmic death pathways as well as sensitize mitochondria to direct proapoptotic stimuli. Additionally, the existence of BCL-2-regulated initiator procaspase activation complexes at the ER membrane has also been described. Here, we review the potential underlying mechanisms involved in these events and discuss pathways for ER-mitochondrial crosstalk pertinent to a number of cell death stimuli.
Breckenridge
David G
DG
Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montreal, Quebec, Canada H3G 1Y6.
Germain
Marc
M
Mathai
Jaigi P
JP
Nguyen
Mai
M
Shore
Gordon C
GC
D016564:Amyloid beta-Protein Precursor / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D020169:Caspases / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology; D008928:Mitochondria / Q000502:physiology; D010446:Peptide Fragments / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors / Q000378:metabolism; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein
D016564:Amyloid beta-Protein Precursor; C494772:BAK1 protein, human; C494826:BAX protein, human; C091247:BCAP31 protein, human; C474007:Bax protein (53-86); D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C497390:SREBF2 protein, human; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D020169:Caspases; D002118:Calcium