title: Isolation of Bcl-2 binding proteins that exhibit homology with BAG-1 and suppressor of death domains protein.
abstract: The Bcl-2 oncoprotein is a potent inhibitor of apoptosis and is overexpressed in a variety of different malignancies. Bcl-2 function is regulated through heterodimerization with other members of the Bcl-2 protein family. In addition, several proteins that are not members of the Bcl-2 family can bind to Bcl-2, including BAG-1 protein. In this study, we screened for proteins that bind to Bcl-2, and isolated two additional members of the BAG-1 protein family, BAG-3 and BAG-4. The BAG-4 protein that we cloned also corresponds to the recently isolated suppressor of death domains (SODD) protein, a molecule that binds and inhibits signaling by tumor necrosis factor receptor 1 (TNFR1). Both BAG-3 and BAG-4/SODD were found to physically associate with Bcl-2, and both proteins are well conserved from human to mouse. A region of homology, comprising 68 amino acids, is present in the carboxyl termini of BAG-3 and BAG-4/SODD, and this region corresponds with sequences termed BAG domains that are found in other members of the BAG-1 protein family. In BAG-3 and BAG-4/SODD, the BAG domains appear to constitute the Bcl-2 binding regions of these molecules. BAG-3 and BAG-4/SODD, like BAG-1, were also shown to bind to Hsp70 inside the cell. Moreover, BAG-3 overexpression modestly inhibited apoptosis resulting from cytokine deprivation of IL-3-dependent 32D cells. Together, our findings demonstrate that other members of the BAG-1 protein family, namely BAG-3 and BAG-4/SODD, bind to Bcl-2 and provide a potential link between pathways regulated by Bcl-2 and pathways regulated by Hsp70, as well as TNFR1.
authors.affiliation: Department of Medicine, Department of Pharmacology, University of Pittsburgh, University of Pittsburgh Cancer Institute, BST E1055, 211 Lothrop Street, Pittsburgh, Pennsylvania 15213-2582, USA.
authors.forename: K
authors.initials: K
authors.lastname: Antoku
authors.forename: R S
authors.initials: RS
authors.lastname: Maser
authors.forename: W J
authors.initials: WJ
authors.lastname: Scully
authors.forename: S M
authors.initials: SM
authors.lastname: Delach
authors.forename: D E
authors.initials: DE
authors.lastname: Johnson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins; D016367:Baculoviridae / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000302:isolation & purification; D002460:Cell Line; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins; D015723:Gene Library; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007313:Insecta; D007377:Interleukin-3 / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014157:Transcription Factors; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD; D051017:Apoptosis Regulatory Proteins; C414431:BAG3 protein, human; C116906:BAG4 protein, human; C091732:BCL2-associated athanogene 1 protein; C498806:Bag3 protein, mouse; C487979:Bag4 protein, mouse; D002352:Carrier Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D007377:Interleukin-3; D019253:Proto-Oncogene Proteins c-bcl-2; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors