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Nutrient/serum starvation derived TRIP-Br3 down-regulation accelerates apoptosis by destabilizing XIAP.

Li C, Jung S, Lee S, Jeong D, Yang Y, Kim KI, Lim JS, Cheon CI, Kim C, Kang YS, Lee MS - Oncotarget (2015)

Bottom Line: However, the prolonged extreme stressful condition of nutrient starvation causes a dramatic decrease of TRIP-Br3, which in turn induces apoptosis by destabilizing XIAP.Up-regulated TRIP-Br1 in cancer cells compensates this effect and delays apoptosis.This can be explained by the competitive alternative binding of TRIP-Br3 and TRIP-Br1 to the BIR2 domain of XIAP.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Systems, Sookmyung Women's University, Seoul, 140-742, South Korea.

ABSTRACT
TRIP-Br3 and TRIP-Br1 have shown to have important biological functions. However, the function of TRIP-Br3 in tumorigenesis is not well characterized compared to oncogenic TRIP-Br1. Here, we investigated the function of TRIP-Br3 in tumorigenesis by comparing with that of TRIP-Br1. Under nutrient/serum starvation, TRIP-Br3 expression was down-regulated slightly in cancer cells and significantly in normal cells. Unexpectedly, TRIP-Br1 expression was greatly up-regulated in cancer cells but not in normal cells. Moreover, TRIP-Br3 activated autophagy while TRIP-Br1 inactivated it under serum starvation. In spite of different expression and roles of TRIP-Br3 and TRIP-Br1, both of them alleviate cell death by directly binding to and stabilizing XIAP, a potent apoptosis inhibitor, through blocking its ubiquitination. Taken together, we propose that TRIP-Br3 primarily activates the autophagy and suppresses apoptosis in nutrient sufficient condition. However, the prolonged extreme stressful condition of nutrient starvation causes a dramatic decrease of TRIP-Br3, which in turn induces apoptosis by destabilizing XIAP. Up-regulated TRIP-Br1 in cancer cells compensates this effect and delays apoptosis. This can be explained by the competitive alternative binding of TRIP-Br3 and TRIP-Br1 to the BIR2 domain of XIAP. In an extended study, our immunohistochemical analysis revealed a markedly lower level of TRIP-Br3 protein in human carcinoma tissues compared to normal epithelial tissues, implying the role of TRIP-Br3 as a tumor suppressor rather than onco-protein.

No MeSH data available.


Related in: MedlinePlus

Inhibitory role of TRIP-Br3 in serum depletion induced cell death(A) Different expression levels of TRIP-Br3 gene in nine cancer cell lines. B, C, D, and E. TRIP-Br3 gene was overexpressed or suppressed by transiently transfecting with TRIP-Br3 silencing RNAs (siTRIP-Br3) or TRIP-Br3 overexpressing plasmid (pEF/TRIP-Br3) with corresponding controls (scRNA or pEF-BOS-EX) as detailed in Methods and Materials. Transfected cells were then incubated in the complete (CM) or serum starved (SS) medium for the indicated times. Microscopic phenotypes of each cell line were photographed (B). Transfected MDA-MB-231 cells were harvested and stained with Annexin V-FITC/propidium iodide for Flow Cytometry Analysis to quantify the serum starvation induced cell death (C) Each protein level was checked using Western blot (D) HEK293T cells were transfected with TRIP-Br3 overexpressing plasmid (pEF/TRIP-Br3) and then treated with 20 μM of etoposide for 48 h (E).
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Figure 3: Inhibitory role of TRIP-Br3 in serum depletion induced cell death(A) Different expression levels of TRIP-Br3 gene in nine cancer cell lines. B, C, D, and E. TRIP-Br3 gene was overexpressed or suppressed by transiently transfecting with TRIP-Br3 silencing RNAs (siTRIP-Br3) or TRIP-Br3 overexpressing plasmid (pEF/TRIP-Br3) with corresponding controls (scRNA or pEF-BOS-EX) as detailed in Methods and Materials. Transfected cells were then incubated in the complete (CM) or serum starved (SS) medium for the indicated times. Microscopic phenotypes of each cell line were photographed (B). Transfected MDA-MB-231 cells were harvested and stained with Annexin V-FITC/propidium iodide for Flow Cytometry Analysis to quantify the serum starvation induced cell death (C) Each protein level was checked using Western blot (D) HEK293T cells were transfected with TRIP-Br3 overexpressing plasmid (pEF/TRIP-Br3) and then treated with 20 μM of etoposide for 48 h (E).

Mentions: To elucidate the role of TRIP-Br3 under the nutrient deficient stressful conditions, TRIP-Br3 expression levels were at first compared in nine different cancer cell lines. The highest and lowest TRIP-Br3 levels were detected in MDA-MB-231 and HEK293T cells, respectively (Figure 3A). Therefore, they were chosen for the suppression or overexpression of TRIP-Br3 gene. Interestingly, MDA-MB-231 cells treated with TRIP-Br3 silencing siTRIP-Br3 were much more sensitive to serum starvation-induced cell death compared to control cells, whereas HEK293T cells transfected with TRIP-Br3 overexpressing pEF/TRIP-Br3 vector showed the similar result with control cells (Figure 3B). This data suggest that down-regulation of TRIP-Br3 induces cell death. This conclusion was supported with FACS analysis as shown in Figure 3C. Both in complete or serum starved media, the cell death rates were much higher (~13.1% and ~25.7%) in MDA-MB-231 cells treated with TRIP-Br3 silencing siTRIP-Br3 compared to control cells (~7.7% and ~15.7%).


Nutrient/serum starvation derived TRIP-Br3 down-regulation accelerates apoptosis by destabilizing XIAP.

Li C, Jung S, Lee S, Jeong D, Yang Y, Kim KI, Lim JS, Cheon CI, Kim C, Kang YS, Lee MS - Oncotarget (2015)

Inhibitory role of TRIP-Br3 in serum depletion induced cell death(A) Different expression levels of TRIP-Br3 gene in nine cancer cell lines. B, C, D, and E. TRIP-Br3 gene was overexpressed or suppressed by transiently transfecting with TRIP-Br3 silencing RNAs (siTRIP-Br3) or TRIP-Br3 overexpressing plasmid (pEF/TRIP-Br3) with corresponding controls (scRNA or pEF-BOS-EX) as detailed in Methods and Materials. Transfected cells were then incubated in the complete (CM) or serum starved (SS) medium for the indicated times. Microscopic phenotypes of each cell line were photographed (B). Transfected MDA-MB-231 cells were harvested and stained with Annexin V-FITC/propidium iodide for Flow Cytometry Analysis to quantify the serum starvation induced cell death (C) Each protein level was checked using Western blot (D) HEK293T cells were transfected with TRIP-Br3 overexpressing plasmid (pEF/TRIP-Br3) and then treated with 20 μM of etoposide for 48 h (E).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4480697&req=5

Figure 3: Inhibitory role of TRIP-Br3 in serum depletion induced cell death(A) Different expression levels of TRIP-Br3 gene in nine cancer cell lines. B, C, D, and E. TRIP-Br3 gene was overexpressed or suppressed by transiently transfecting with TRIP-Br3 silencing RNAs (siTRIP-Br3) or TRIP-Br3 overexpressing plasmid (pEF/TRIP-Br3) with corresponding controls (scRNA or pEF-BOS-EX) as detailed in Methods and Materials. Transfected cells were then incubated in the complete (CM) or serum starved (SS) medium for the indicated times. Microscopic phenotypes of each cell line were photographed (B). Transfected MDA-MB-231 cells were harvested and stained with Annexin V-FITC/propidium iodide for Flow Cytometry Analysis to quantify the serum starvation induced cell death (C) Each protein level was checked using Western blot (D) HEK293T cells were transfected with TRIP-Br3 overexpressing plasmid (pEF/TRIP-Br3) and then treated with 20 μM of etoposide for 48 h (E).
Mentions: To elucidate the role of TRIP-Br3 under the nutrient deficient stressful conditions, TRIP-Br3 expression levels were at first compared in nine different cancer cell lines. The highest and lowest TRIP-Br3 levels were detected in MDA-MB-231 and HEK293T cells, respectively (Figure 3A). Therefore, they were chosen for the suppression or overexpression of TRIP-Br3 gene. Interestingly, MDA-MB-231 cells treated with TRIP-Br3 silencing siTRIP-Br3 were much more sensitive to serum starvation-induced cell death compared to control cells, whereas HEK293T cells transfected with TRIP-Br3 overexpressing pEF/TRIP-Br3 vector showed the similar result with control cells (Figure 3B). This data suggest that down-regulation of TRIP-Br3 induces cell death. This conclusion was supported with FACS analysis as shown in Figure 3C. Both in complete or serum starved media, the cell death rates were much higher (~13.1% and ~25.7%) in MDA-MB-231 cells treated with TRIP-Br3 silencing siTRIP-Br3 compared to control cells (~7.7% and ~15.7%).

Bottom Line: However, the prolonged extreme stressful condition of nutrient starvation causes a dramatic decrease of TRIP-Br3, which in turn induces apoptosis by destabilizing XIAP.Up-regulated TRIP-Br1 in cancer cells compensates this effect and delays apoptosis.This can be explained by the competitive alternative binding of TRIP-Br3 and TRIP-Br1 to the BIR2 domain of XIAP.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Systems, Sookmyung Women's University, Seoul, 140-742, South Korea.

ABSTRACT
TRIP-Br3 and TRIP-Br1 have shown to have important biological functions. However, the function of TRIP-Br3 in tumorigenesis is not well characterized compared to oncogenic TRIP-Br1. Here, we investigated the function of TRIP-Br3 in tumorigenesis by comparing with that of TRIP-Br1. Under nutrient/serum starvation, TRIP-Br3 expression was down-regulated slightly in cancer cells and significantly in normal cells. Unexpectedly, TRIP-Br1 expression was greatly up-regulated in cancer cells but not in normal cells. Moreover, TRIP-Br3 activated autophagy while TRIP-Br1 inactivated it under serum starvation. In spite of different expression and roles of TRIP-Br3 and TRIP-Br1, both of them alleviate cell death by directly binding to and stabilizing XIAP, a potent apoptosis inhibitor, through blocking its ubiquitination. Taken together, we propose that TRIP-Br3 primarily activates the autophagy and suppresses apoptosis in nutrient sufficient condition. However, the prolonged extreme stressful condition of nutrient starvation causes a dramatic decrease of TRIP-Br3, which in turn induces apoptosis by destabilizing XIAP. Up-regulated TRIP-Br1 in cancer cells compensates this effect and delays apoptosis. This can be explained by the competitive alternative binding of TRIP-Br3 and TRIP-Br1 to the BIR2 domain of XIAP. In an extended study, our immunohistochemical analysis revealed a markedly lower level of TRIP-Br3 protein in human carcinoma tissues compared to normal epithelial tissues, implying the role of TRIP-Br3 as a tumor suppressor rather than onco-protein.

No MeSH data available.


Related in: MedlinePlus