Bc1-2, Raf-1 and mitochondrial regulation of apoptosis.
Raf-1 kinase was shown to bind via its catalytic domain (Cat) to Bcl-2 in a BH4 domain-dependent manner. Using a green fluorescent protein (GFP)-Raf-1 (Cat) fusion protein, Bcl-2 but not Bcl-2(delta BH4) was found to target Raf-1 to mitochondria in cells. Targeting Raf-1 (Cat) to mitochondrial membranes by fusing with the transmembrane domain of an outer mitochondrial membrane protein protected cells from apoptosis and resulted in phosphorylation of BAD protein, whereas plasma-membrane targeted Raf-1 failed to phosphorylate BAD and did not protect against cell death. Moreover, a Bcl-2 binding protein, BAG-1, was shown to not only bind Raf-1, but also increase the activity of this kinase through a protein-protein interaction. The findings suggest that Bcl-2 targets Raf-1 to mitochondria, allowing this kinase to contribute to cellular survival by phosphorylating BAD or possibly other protein substrates in the vicinity of Bcl-2.
Wang
H G
HG
Burnham Institute, La Jolla, CA 92037, USA. hgwang@ljcrf.edu
Reed
J C
JC
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D020134:Catalytic Domain; D002460:Cell Line; D006706:Homeostasis; D006801:Humans; D007425:Intracellular Membranes / Q000502:physiology; D008928:Mitochondria / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D019908:Proto-Oncogene Proteins c-raf