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Hypoxia-induced MIR155 is a potent autophagy inducer by targeting multiple players in the MTOR pathway.

Wan G, Xie W, Liu Z, Xu W, Lao Y, Huang N, Cui K, Liao M, He J, Jiang Y, Yang BB, Xu H, Xu N, Zhang Y - Autophagy (2013)

Bottom Line: MIR155 suppresses target-gene expression by directly interacting with their 3' untranslated regions (UTRs), mutations of the binding sites abolish their MIR155 responsiveness.Furthermore, by downregulating MTOR signaling, MIR155 also attenuates cell proliferation and induces G 1/S cell cycle arrest.Collectively, these data present a new role for MIR155 as a key regulator of autophagy via dysregulation of MTOR pathway.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences; Tsinghua University; Beijing, China; Key Lab in Healthy Science and Technology; Division of Life Science; Graduate School at Shenzhen; Tsinghua University; Shenzhen, China.

ABSTRACT
Hypoxia activates autophagy, an evolutionarily conserved cellular catabolic process. Dysfunction in the autophagy pathway has been implicated in an increasing number of human diseases, including cancer. Hypoxia induces upregulation of a specific set of microRNAs (miRNAs) in a variety of cell types. Here, we describe hypoxia-induced MIR155 as a potent inducer of autophagy. Enforced expression of MIR155 increases autophagic activity in human nasopharyngeal cancer and cervical cancer cells. Knocking down endogenous MIR155 inhibits hypoxia-induced autophagy. We demonstrated that MIR155 targets multiple players in MTOR signaling, including RHEB, RICTOR, and RPS6KB2. MIR155 suppresses target-gene expression by directly interacting with their 3' untranslated regions (UTRs), mutations of the binding sites abolish their MIR155 responsiveness. Furthermore, by downregulating MTOR signaling, MIR155 also attenuates cell proliferation and induces G 1/S cell cycle arrest. Collectively, these data present a new role for MIR155 as a key regulator of autophagy via dysregulation of MTOR pathway.

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Figure 1. Hypoxia-induced MIR155 promotes autophagosome accumulation. (A) Hypoxia induces MIR155 expression. CNE or HeLa cells were exposed to 1% oxygen for 24, 36 and 48 h. Cells were collected for qRT-PCR to quantify the expression of MIR155. (mean ± s.d. of independent experiments, n = 4, *P < 0.05, **P < 0.01, ***P < 0.001, Student 2-tailed t test). (B) MIR155 promotes GFP-LC3 translocation. CNE or HeLa cells stably expressing GFP-LC3 were transfected with negative control (NC), MIR155 or MIR203. Cells were fixed 48 h post transfection. Representative images are shown. Scale bar: 10 μm. (C) Quantitative analysis of GFP-LC3 puncta in (B). At least 200 cells were examined in each experimental group. Data shown are means ± s.d. of four independent experiments. **P < 0.01, Wilcoxon rank sum test.
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Figure 1: Figure 1. Hypoxia-induced MIR155 promotes autophagosome accumulation. (A) Hypoxia induces MIR155 expression. CNE or HeLa cells were exposed to 1% oxygen for 24, 36 and 48 h. Cells were collected for qRT-PCR to quantify the expression of MIR155. (mean ± s.d. of independent experiments, n = 4, *P < 0.05, **P < 0.01, ***P < 0.001, Student 2-tailed t test). (B) MIR155 promotes GFP-LC3 translocation. CNE or HeLa cells stably expressing GFP-LC3 were transfected with negative control (NC), MIR155 or MIR203. Cells were fixed 48 h post transfection. Representative images are shown. Scale bar: 10 μm. (C) Quantitative analysis of GFP-LC3 puncta in (B). At least 200 cells were examined in each experimental group. Data shown are means ± s.d. of four independent experiments. **P < 0.01, Wilcoxon rank sum test.

Mentions: To investigate the function of MIR155 in hypoxia-induced autophagy, first we examined the expression of MIR155 in CNE and HeLa cells under hypoxic stress. As shown in Figure 1A, the expression level of MIR155 was low in normal culture conditions (21% oxygen). Hypoxia (1% oxygen) treatment induced a sustained upregulation of MIR155 in a time-dependent manner in both cell types. At 48 h after hypoxia treatment, more than a 12-fold increase of the MIR155 expression level was detected.


Hypoxia-induced MIR155 is a potent autophagy inducer by targeting multiple players in the MTOR pathway.

Wan G, Xie W, Liu Z, Xu W, Lao Y, Huang N, Cui K, Liao M, He J, Jiang Y, Yang BB, Xu H, Xu N, Zhang Y - Autophagy (2013)

Figure 1. Hypoxia-induced MIR155 promotes autophagosome accumulation. (A) Hypoxia induces MIR155 expression. CNE or HeLa cells were exposed to 1% oxygen for 24, 36 and 48 h. Cells were collected for qRT-PCR to quantify the expression of MIR155. (mean ± s.d. of independent experiments, n = 4, *P < 0.05, **P < 0.01, ***P < 0.001, Student 2-tailed t test). (B) MIR155 promotes GFP-LC3 translocation. CNE or HeLa cells stably expressing GFP-LC3 were transfected with negative control (NC), MIR155 or MIR203. Cells were fixed 48 h post transfection. Representative images are shown. Scale bar: 10 μm. (C) Quantitative analysis of GFP-LC3 puncta in (B). At least 200 cells were examined in each experimental group. Data shown are means ± s.d. of four independent experiments. **P < 0.01, Wilcoxon rank sum test.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 1: Figure 1. Hypoxia-induced MIR155 promotes autophagosome accumulation. (A) Hypoxia induces MIR155 expression. CNE or HeLa cells were exposed to 1% oxygen for 24, 36 and 48 h. Cells were collected for qRT-PCR to quantify the expression of MIR155. (mean ± s.d. of independent experiments, n = 4, *P < 0.05, **P < 0.01, ***P < 0.001, Student 2-tailed t test). (B) MIR155 promotes GFP-LC3 translocation. CNE or HeLa cells stably expressing GFP-LC3 were transfected with negative control (NC), MIR155 or MIR203. Cells were fixed 48 h post transfection. Representative images are shown. Scale bar: 10 μm. (C) Quantitative analysis of GFP-LC3 puncta in (B). At least 200 cells were examined in each experimental group. Data shown are means ± s.d. of four independent experiments. **P < 0.01, Wilcoxon rank sum test.
Mentions: To investigate the function of MIR155 in hypoxia-induced autophagy, first we examined the expression of MIR155 in CNE and HeLa cells under hypoxic stress. As shown in Figure 1A, the expression level of MIR155 was low in normal culture conditions (21% oxygen). Hypoxia (1% oxygen) treatment induced a sustained upregulation of MIR155 in a time-dependent manner in both cell types. At 48 h after hypoxia treatment, more than a 12-fold increase of the MIR155 expression level was detected.

Bottom Line: MIR155 suppresses target-gene expression by directly interacting with their 3' untranslated regions (UTRs), mutations of the binding sites abolish their MIR155 responsiveness.Furthermore, by downregulating MTOR signaling, MIR155 also attenuates cell proliferation and induces G 1/S cell cycle arrest.Collectively, these data present a new role for MIR155 as a key regulator of autophagy via dysregulation of MTOR pathway.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences; Tsinghua University; Beijing, China; Key Lab in Healthy Science and Technology; Division of Life Science; Graduate School at Shenzhen; Tsinghua University; Shenzhen, China.

ABSTRACT
Hypoxia activates autophagy, an evolutionarily conserved cellular catabolic process. Dysfunction in the autophagy pathway has been implicated in an increasing number of human diseases, including cancer. Hypoxia induces upregulation of a specific set of microRNAs (miRNAs) in a variety of cell types. Here, we describe hypoxia-induced MIR155 as a potent inducer of autophagy. Enforced expression of MIR155 increases autophagic activity in human nasopharyngeal cancer and cervical cancer cells. Knocking down endogenous MIR155 inhibits hypoxia-induced autophagy. We demonstrated that MIR155 targets multiple players in MTOR signaling, including RHEB, RICTOR, and RPS6KB2. MIR155 suppresses target-gene expression by directly interacting with their 3' untranslated regions (UTRs), mutations of the binding sites abolish their MIR155 responsiveness. Furthermore, by downregulating MTOR signaling, MIR155 also attenuates cell proliferation and induces G 1/S cell cycle arrest. Collectively, these data present a new role for MIR155 as a key regulator of autophagy via dysregulation of MTOR pathway.

Show MeSH
Related in: MedlinePlus