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lncRNA NBR2 engages a metabolic checkpoint by regulating AMPK under energy stress

View Article: PubMed Central - PubMed

ABSTRACT

Long noncoding RNAs (lncRNAs) have emerged as critical regulators in various cellular processes. However, the potential involvement of lncRNAs in kinase signaling remains largely unknown. AMP-activated protein kinase (AMPK) acts as a critical sensor of cellular energy status. Here we show that lncRNA NBR2 (neighbor of BRCA1 gene 2) is induced by the LKB1-AMPK pathway under energy stress. Upon energy stress, NBR2 in turn interacts with AMPK and promotes AMPK kinase activity, thus forming a feed-forward loop to potentiate AMPK activation during energy stress. Depletion of NBR2 attenuates energy stress-induced AMPK activation, resulting in unchecked cell cycling, altered apoptosis/autophagy response, and increased tumor development in vivo. NBR2 is down-regulated and its low expression correlates with poor clinical outcomes in some human cancers. Together, our study uncovers a mechanism coupling lncRNAs with metabolic stress response, and provides a broad framework to further understand the regulation of kinase signaling by lncRNAs.

No MeSH data available.


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NBR2 inhibits tumor development(a, b) 786-O (a) or MDA-MB-231 cells (b) infected with either control shRNA or NBR2 shRNA were seeded in soft agar containing high or low concentrations of glucose as indicated. Bar graph showing the mean colony numbers from the soft agar assay (Mean ± s.d., n=5 fields per group, each field was assessed from an independent experiment, two-tailed paired Student’s t-test). (c) Relative tumor volumes of MDA-MB-231 xenograft tumors infected with either control shRNA or NBR2 shRNA at different weeks (Mean ± s.e.m., n = 5 xenograft tumors, *: P < 0.05; **: P < 0.01 two-tailed paired Student’s t-test). (d) Protein lysates obtained from xenograft tumors infected with either control shRNA or NBR2 shRNA at the end point were subjected to Western blotting analysis as indicated. (e, f) The box plot showing the expression pattern of NBR2 for each pair of tumor and normal samples in BRCA (e, n=104 matched pairs, Sutdent's t-test and Wilcoxon test) and KIRC (f, n=65 matched pairs, Sutdent's t-test and Wilcoxon test). The boxes show the median ±1 quartile, with whiskers extending to the most extreme data point within 1.5 interquartile range from the box boundaries. (g) Kaplan Meier plots of breast cancer patients stratified by the expression levels of NBR2 (nhigh = 1767, nlow = 1787, Log-Rank Test). Unprocessed original scans of blots are shown in Supplemental Fig. 8.
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Figure 4: NBR2 inhibits tumor development(a, b) 786-O (a) or MDA-MB-231 cells (b) infected with either control shRNA or NBR2 shRNA were seeded in soft agar containing high or low concentrations of glucose as indicated. Bar graph showing the mean colony numbers from the soft agar assay (Mean ± s.d., n=5 fields per group, each field was assessed from an independent experiment, two-tailed paired Student’s t-test). (c) Relative tumor volumes of MDA-MB-231 xenograft tumors infected with either control shRNA or NBR2 shRNA at different weeks (Mean ± s.e.m., n = 5 xenograft tumors, *: P < 0.05; **: P < 0.01 two-tailed paired Student’s t-test). (d) Protein lysates obtained from xenograft tumors infected with either control shRNA or NBR2 shRNA at the end point were subjected to Western blotting analysis as indicated. (e, f) The box plot showing the expression pattern of NBR2 for each pair of tumor and normal samples in BRCA (e, n=104 matched pairs, Sutdent's t-test and Wilcoxon test) and KIRC (f, n=65 matched pairs, Sutdent's t-test and Wilcoxon test). The boxes show the median ±1 quartile, with whiskers extending to the most extreme data point within 1.5 interquartile range from the box boundaries. (g) Kaplan Meier plots of breast cancer patients stratified by the expression levels of NBR2 (nhigh = 1767, nlow = 1787, Log-Rank Test). Unprocessed original scans of blots are shown in Supplemental Fig. 8.

Mentions: Given the important functions of AMPK in the regulation of human cancers22, we next examined the potential roles of NBR2 in tumor development. NBR2 deficiency led to increased anchorage-independent growth, one of the hallmarks of cell transformation, with a more prominent effect under glucose starvation conditions (Fig. 4a, b). In vivo experiments using the xenograft model showed that NBR2 deficiency increased tumor development (Fig. 4c). Further analyses of the tumor samples by Western blotting confirmed down-regulation of AMPK and up-regulation of mTORC1 signaling in NBR2 deficient tumors (Fig. 4d).


lncRNA NBR2 engages a metabolic checkpoint by regulating AMPK under energy stress
NBR2 inhibits tumor development(a, b) 786-O (a) or MDA-MB-231 cells (b) infected with either control shRNA or NBR2 shRNA were seeded in soft agar containing high or low concentrations of glucose as indicated. Bar graph showing the mean colony numbers from the soft agar assay (Mean ± s.d., n=5 fields per group, each field was assessed from an independent experiment, two-tailed paired Student’s t-test). (c) Relative tumor volumes of MDA-MB-231 xenograft tumors infected with either control shRNA or NBR2 shRNA at different weeks (Mean ± s.e.m., n = 5 xenograft tumors, *: P < 0.05; **: P < 0.01 two-tailed paired Student’s t-test). (d) Protein lysates obtained from xenograft tumors infected with either control shRNA or NBR2 shRNA at the end point were subjected to Western blotting analysis as indicated. (e, f) The box plot showing the expression pattern of NBR2 for each pair of tumor and normal samples in BRCA (e, n=104 matched pairs, Sutdent's t-test and Wilcoxon test) and KIRC (f, n=65 matched pairs, Sutdent's t-test and Wilcoxon test). The boxes show the median ±1 quartile, with whiskers extending to the most extreme data point within 1.5 interquartile range from the box boundaries. (g) Kaplan Meier plots of breast cancer patients stratified by the expression levels of NBR2 (nhigh = 1767, nlow = 1787, Log-Rank Test). Unprocessed original scans of blots are shown in Supplemental Fig. 8.
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Figure 4: NBR2 inhibits tumor development(a, b) 786-O (a) or MDA-MB-231 cells (b) infected with either control shRNA or NBR2 shRNA were seeded in soft agar containing high or low concentrations of glucose as indicated. Bar graph showing the mean colony numbers from the soft agar assay (Mean ± s.d., n=5 fields per group, each field was assessed from an independent experiment, two-tailed paired Student’s t-test). (c) Relative tumor volumes of MDA-MB-231 xenograft tumors infected with either control shRNA or NBR2 shRNA at different weeks (Mean ± s.e.m., n = 5 xenograft tumors, *: P < 0.05; **: P < 0.01 two-tailed paired Student’s t-test). (d) Protein lysates obtained from xenograft tumors infected with either control shRNA or NBR2 shRNA at the end point were subjected to Western blotting analysis as indicated. (e, f) The box plot showing the expression pattern of NBR2 for each pair of tumor and normal samples in BRCA (e, n=104 matched pairs, Sutdent's t-test and Wilcoxon test) and KIRC (f, n=65 matched pairs, Sutdent's t-test and Wilcoxon test). The boxes show the median ±1 quartile, with whiskers extending to the most extreme data point within 1.5 interquartile range from the box boundaries. (g) Kaplan Meier plots of breast cancer patients stratified by the expression levels of NBR2 (nhigh = 1767, nlow = 1787, Log-Rank Test). Unprocessed original scans of blots are shown in Supplemental Fig. 8.
Mentions: Given the important functions of AMPK in the regulation of human cancers22, we next examined the potential roles of NBR2 in tumor development. NBR2 deficiency led to increased anchorage-independent growth, one of the hallmarks of cell transformation, with a more prominent effect under glucose starvation conditions (Fig. 4a, b). In vivo experiments using the xenograft model showed that NBR2 deficiency increased tumor development (Fig. 4c). Further analyses of the tumor samples by Western blotting confirmed down-regulation of AMPK and up-regulation of mTORC1 signaling in NBR2 deficient tumors (Fig. 4d).

View Article: PubMed Central - PubMed

ABSTRACT

Long noncoding RNAs (lncRNAs) have emerged as critical regulators in various cellular processes. However, the potential involvement of lncRNAs in kinase signaling remains largely unknown. AMP-activated protein kinase (AMPK) acts as a critical sensor of cellular energy status. Here we show that lncRNA NBR2 (neighbor of BRCA1 gene 2) is induced by the LKB1-AMPK pathway under energy stress. Upon energy stress, NBR2 in turn interacts with AMPK and promotes AMPK kinase activity, thus forming a feed-forward loop to potentiate AMPK activation during energy stress. Depletion of NBR2 attenuates energy stress-induced AMPK activation, resulting in unchecked cell cycling, altered apoptosis/autophagy response, and increased tumor development in vivo. NBR2 is down-regulated and its low expression correlates with poor clinical outcomes in some human cancers. Together, our study uncovers a mechanism coupling lncRNAs with metabolic stress response, and provides a broad framework to further understand the regulation of kinase signaling by lncRNAs.

No MeSH data available.


Related in: MedlinePlus