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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.

SUBMITTER: Ambrosini G

PROVIDER: S-EPMC2733857 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Differentiation-related gene-1 decreases Bim stability by proteasome-mediated degradation.

Ambrosini Grazia G Seelman Sharon L SL Schwartz Gary K GK

Cancer research 20090721 15

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-regul ...[more]

PMID: 19622774

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Project description:The key pathogenic steps leading to spinal muscular atrophy (SMA), a genetic disease characterized by selective motor neuron degeneration, are not fully clarified. The full-length SMN protein (FL-SMN), the main protein product of the disease gene SMN1, plays an established role in the cytoplasm in snRNP biogenesis ultimately leading to mRNA splicing within the nucleus. It is also involved in the mRNA axonal transport. However, to what extent the impairment of these two SMN functions contributes to SMA pathogenesis remains unknown. A shorter SMN isoform, axonal-SMN or a-SMN, with more specific axonal localization, has been discovered, but whether it might act in concert with FL-SMN in SMA pathogenesis is not known. As a first step in defining common or divergent intracellular roles of FL-SMN vs a-SMN proteins, we here characterized the turn-over of both proteins and investigated which pathway contributed to a-SMN degradation. We performed real time western blot and confocal immunofluorescence analysis in easily controllable in vitro settings. We analyzed co-transfected NSC34 and HeLa cells and cell clones stably expressing both a-SMN and FL-SMN proteins after specific blocking of transcript or protein synthesis and inhibition of known intracellular degradation pathways. Our data indicated that whereas the stability of both FL-SMN and a-SMN transcripts was comparable, the a-SMN protein was characterized by a much shorter half-life than FL-SMN. In addition, as already demonstrated for FL-SMN, the Ub/proteasome pathway played a major role in the a-SMN protein degradation. We hypothesize that the faster degradation rate of a-SMN vs FL-SMN is related to the protection provided by the protein complex in which FL-SMN is assembled. The diverse a-SMN vs FL-SMN C-terminus may dictate different protein interactions and complex formation explaining the different localization and role in the neuronal compartment, and the lower expression and stability of a-SMN.

Dataset Information

Differentiation-related gene-1 decreases Bim stability by proteasome-mediated degradation.

Publications

Differentiation-related gene-1 decreases Bim stability by proteasome-mediated degradation.

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