title: Differentiation-related gene-1 decreases Bim stability by proteasome-mediated degradation.
abstract: Drg1 was identified as a differentiation-related, putative metastatic suppressor gene in human colon and prostate cancer. Its expression is associated with resistance to irinotecan (CPT-11) therapy in preclinical colorectal cancer models both in vitro and in vivo. However, the functional significance of Drg1 in these processes is unknown. We have shown for the first time that Drg1 directly binds to the BH3-only proapoptotic protein Bim. Depletion of Drg1 by small interfering RNA induced up-regulation of Bim and its accumulation in the mitochondria, which correlated with loss of mitochondrial membrane potential and induction of apoptosis in cells exposed to SN-38. Further analyses revealed that Drg1 promotes degradation of Bim through the Cullin2/ElonginB-CIS ubiquitin-protein ligase complex. Conversely, in the absence of Drg1, Bim was stabilized and bound more abundantly to Hsp70. These results show that Drg1 renders cancer cells more resistant to chemotherapy through enhanced proteasome-mediated Bim degradation.
authors.affiliation: Department of Medicine, Laboratory of New Drug Development, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: Grazia
authors.initials: G
authors.lastname: Ambrosini
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Seelman
authors.forename: Gary K
authors.initials: GK
authors.lastname: Schwartz
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D002166:Camptothecin / Q000031:analogs & derivatives / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D016373:DNA, Antisense / Q000235:genetics; D015536:Down-Regulation; D019204:GTP-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D045325:HCT116 Cells; D006801:Humans; D000077146:Irinotecan; D008565:Membrane Proteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D016373:DNA, Antisense; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; C078418:developmentally regulated GTP-binding protein; D000077146:Irinotecan; D046988:Proteasome Endopeptidase Complex; D019204:GTP-Binding Proteins; D002166:Camptothecin