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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 6. Blockage of endogenous MIR155 led to an increase in RHEB, RICTOR, and RPS6KB2 protein levels. Western blot analysis of RHEB, RICTOR, RPS6KB2, MTOR, phospho-MTOR (Ser2448), and GAPDH in CNE or HeLa cells transfected with LNA-NC or LNA-155. Protein ratios were calculated following ImageJ densitometric analysis. (3 independent experiments gave similar results).
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Figure 6: Figure 6. Blockage of endogenous MIR155 led to an increase in RHEB, RICTOR, and RPS6KB2 protein levels. Western blot analysis of RHEB, RICTOR, RPS6KB2, MTOR, phospho-MTOR (Ser2448), and GAPDH in CNE or HeLa cells transfected with LNA-NC or LNA-155. Protein ratios were calculated following ImageJ densitometric analysis. (3 independent experiments gave similar results).

Mentions: To test whether silencing endogenous MIR155 would have an impact on target protein expression, we transfected cells with antagomir-155 (LNA-155) or nonspecific control antagomir (LNA-NC). Then, we checked the protein expression levels of RHEB, RICTOR, and RPS6KB2 by western blot. We showed that hypoxia induced downregulation of RHEB, RICTOR, and RPS6KB2 proteins. The amounts of all 3 proteins were increased when hypoxia-induced upregulation of MIR155 was suppressed by LNA-155. In addition, there was a clear increase of in the phosphorylation of MTOR (Ser2448) (Fig. 6; Fig. S5). In the light of these results, we demonstrate that endogenous MIR155 targets the expression of MTOR signaling, and hence the autophagic activity.


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 6. Blockage of endogenous MIR155 led to an increase in RHEB, RICTOR, and RPS6KB2 protein levels. Western blot analysis of RHEB, RICTOR, RPS6KB2, MTOR, phospho-MTOR (Ser2448), and GAPDH in CNE or HeLa cells transfected with LNA-NC or LNA-155. Protein ratios were calculated following ImageJ densitometric analysis. (3 independent experiments gave similar results).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389881&req=5

Figure 6: Figure 6. Blockage of endogenous MIR155 led to an increase in RHEB, RICTOR, and RPS6KB2 protein levels. Western blot analysis of RHEB, RICTOR, RPS6KB2, MTOR, phospho-MTOR (Ser2448), and GAPDH in CNE or HeLa cells transfected with LNA-NC or LNA-155. Protein ratios were calculated following ImageJ densitometric analysis. (3 independent experiments gave similar results).
Mentions: To test whether silencing endogenous MIR155 would have an impact on target protein expression, we transfected cells with antagomir-155 (LNA-155) or nonspecific control antagomir (LNA-NC). Then, we checked the protein expression levels of RHEB, RICTOR, and RPS6KB2 by western blot. We showed that hypoxia induced downregulation of RHEB, RICTOR, and RPS6KB2 proteins. The amounts of all 3 proteins were increased when hypoxia-induced upregulation of MIR155 was suppressed by LNA-155. In addition, there was a clear increase of in the phosphorylation of MTOR (Ser2448) (Fig. 6; Fig. S5). In the light of these results, we demonstrate that endogenous MIR155 targets the expression of MTOR signaling, and hence the autophagic activity.

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