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An mTORC1-Mdm2-Drosha axis for miRNA biogenesis in response to glucose- and amino acid-deprivation.

ABSTRACT: mTOR senses nutrient and energy status to regulate cell survival and metabolism in response to environmental changes. Surprisingly, targeted mutation of Tsc1, a negative regulator of mTORC1, caused a broad reduction in miRNAs due to Drosha degradation. Conversely, targeted mutation of Raptor, an essential component of mTORC1, increased miRNA biogenesis. mTOR activation increased expression of Mdm2, which is hereby identified as the necessary and sufficient ubiquitin E3 ligase for Drosha. Drosha was induced by nutrient and energy deprivation and conferred resistance to glucose deprivation. Using a high-throughput screen of a miRNA library, we identified four miRNAs that were necessary and sufficient to protect cells against glucose-deprivation-induced apoptosis. These miRNA was regulated by glucose through the mTORC1-MDM2-DROSHA axis. Taken together, our data reveal an mTOR-Mdm2-Drosha pathway in mammalian cells that broadly regulates miRNA biogenesis as a response to alteration in cellular environment.

SUBMITTER: Ye P

PROVIDER: S-EPMC4511160 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature

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An mTORC1-Mdm2-Drosha axis for miRNA biogenesis in response to glucose- and amino acid-deprivation.

Ye Peiying P Liu Yu Y Chen Chong C Tang Fei F Wu Qi Q Wang Xiang X Liu Chang-Gong CG Liu Xiuping X Liu Runhua R Liu Yang Y Zheng Pan P

Molecular cell 20150129 4

mTOR senses nutrient and energy status to regulate cell survival and metabolism in response to environmental changes. Surprisingly, targeted mutation of Tsc1, a negative regulator of mTORC1, caused a broad reduction in miRNAs due to Drosha degradation. Conversely, targeted mutation of Raptor, an essential component of mTORC1, increased miRNA biogenesis. mTOR activation increased expression of Mdm2, which is hereby identified as the necessary and sufficient ubiquitin E3 ligase for Drosha. Drosha ...[more]

PMID: 25639470

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Project description:Rationale: Post-translational modifications have emerged as vital players in alterations to tumor metabolism, including amino acid metabolic reprogramming. Jumonji domain-containing protein 2B (JMJD2B) enhances colorectal cancer (CRC) cell survival upon glucose deficiency. In the present study, we hypothesized that JMJD2B affects tumor cell amino acid metabolism in CRC and consequently promotes survival of CRC cells upon glucose deprivation. Methods: Non-target metabolic profiling was used to evaluate the roles of JMJD2B in CRC cell metabolism under glucose starvation. The roles of amino acid alterations induced by JMJD2B on CRC cell survival were determined by cell viability, immunoblotting, and clonogenic assays, and flow cytometry. The underlying mechanisms by which JMJD2B affected CRC cell metabolism were assessed using immunofluorescence staining, chromatin immunoprecipitation assays, electron microscopy in CRC cell lines, and using xenograft models. The correlation between JMJD2B and LC3B expression in human CRC specimens was assessed using immunohistochemistry. Results: Profound metabolic reprogramming was detected in JMJD2B knockdown CRC cells under glucose deficiency, especially those involving amino acid metabolites. Silencing of JMJD2B reduced the levels of certain amino acids that were induced by glucose deficiency. Among these amino acids, asparagine (Asn), phenylalanine (Phe), and histidine (His) promoted CRC cell survival under glucose starvation when JMJD2B was knocked down. Mechanistically, downregulation of JMJD2B inhibited autophagy in CRC cells through epigenetic regulation of microtubule associated protein 1 light chain 3 beta (LC3B), and subsequently decreased intracellular amino acid (Asn, Phe, His) levels under glucose deprivation, thus suppressing the survival of CRC cells. Using a nude mouse xenograft model, we verified that inhibiting JMJD2B could decrease the levels of amino acids (Asn, Phe, His). In addition, the inhibitory effects of JMJD2B-knockdown on tumor growth and amino acids level were rescued by overexpression of LC3B. Furthermore, we observed that the high expression of LC3B was more likely detected in tissuses with high expression of JMJD2B (P < 0.001) in 60 human CRC tissues. Conclusion: These results indicated that JMJD2B sustained the intracellular amino acids derived from autophagy in CRC cells upon glucose deficiency, partly through epigenetic regulation of LC3B, thus driving the malignancy of CRC.

Dataset Information

An mTORC1-Mdm2-Drosha axis for miRNA biogenesis in response to glucose- and amino acid-deprivation.

Publications

An mTORC1-Mdm2-Drosha axis for miRNA biogenesis in response to glucose- and amino acid-deprivation.

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