Dataset Information

Negative regulation of the FOXO3a transcription factor by mTORC2 induces a pro-survival response following exposure to ultraviolet-B irradiation.

ABSTRACT: Exposure to ultraviolet-B (UVB) irradiation, the principal cause of non-melanoma skin cancer (NMSC), activates both the rapamycin-sensitive mammalian target of rapamycin complex 1 (mTORC1) and the rapamycin-resistant mTORC2. We have previously reported that UVB-induced keratinocyte survival is dependent on mTORC2, though the specific mechanism is not well understood. FOXO3a is an important transcription factor involved in regulating cell survival. The activity of FOXO3a is reduced as a result of protein kinase B (AKT/PKB) activation, which is downstream of mTORC2; however, the specific function of FOXO3a during UVB-induced apoptosis is unclear. In this study, we establish that in cells with wild-type mTORC2 activity, FOXO3a is quickly phosphorylated in response to UVB and sequestered in the cytoplasm. In contrast, loss of mTORC2 causes FOXO3a to be localized to the nucleus and sensitizes cells to UVB-induced apoptosis. Furthermore, this sensitization is rescued by knockdown of FOXO3a. Taken together, these studies provide strong evidence that inhibition of mTORC2 enhances UVB-induced apoptosis in a FOXO3a-dependent manner, and suggest that FOXO3a activation by mTORC2 inhibitors may be a valuable chemopreventive target in NMSC.

SUBMITTER: Feehan RP

PROVIDER: S-EPMC4899167 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Negative regulation of the FOXO3a transcription factor by mTORC2 induces a pro-survival response following exposure to ultraviolet-B irradiation.

Feehan Robert P RP Shantz Lisa M LM

Cellular signalling 20160404 8

Exposure to ultraviolet-B (UVB) irradiation, the principal cause of non-melanoma skin cancer (NMSC), activates both the rapamycin-sensitive mammalian target of rapamycin complex 1 (mTORC1) and the rapamycin-resistant mTORC2. We have previously reported that UVB-induced keratinocyte survival is dependent on mTORC2, though the specific mechanism is not well understood. FOXO3a is an important transcription factor involved in regulating cell survival. The activity of FOXO3a is reduced as a result of ...[more]

PMID: 27058291

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Project description:Untreated or 20 J/m2 UVC treated RKO cells were collected and RNA from either whole-cell lysates or from polysomal fractions was extracted at 0 (untreated), 3, 6, and 12 h after treatment. RNA from whole-cell lysates or each of 11 polysomal fraction was reverse-transcribed in the presence of [α-33P]dCTP and the radiolabeled product used to hybridize human cDNA arrays. The experiment was repeated using three independent sample sets. The samples were named T-c-A, T-c-B, T-c-C, T-3h-A, T-3h-B, T-3h-C, T-6h-A, T-6h-B, T-6h-C, T-12h-A, T-12h-B, T-12h-C, P-c-1-A, P-c-2-A, P-c-3-A, P-c-4-A, P-c-5-A, P-c-6-A, P-c-7-A, P-c-8-A, P-c-9-A, P-c-10-A, P-c-11-A, P-c-1-B, P-c-2-B, P-c-3-B, P-c-4-B, P-c-5-B, P-c-6-B, P-c-7-B, P-c-8-B, P-c-9-B, P-c-10-B, P-c-11-B, P-c-2-C, P-c-3-C, P-c-4-C, P-c-5-C, P-c-6-C, P-c-7-C, P-c-8-C, P-c-9-C, P-c-10-C, P-c-11-C, P-3h-1-A, P-3h-2-A, P-3h-3-A, P-3h-4-A, P-3h-5-A, P-3h-6-A, P-3h-7-A, P-3h-8-A, P-3h-9-A, P-3h-10-A, P-3h-11-A, P-3h-1-B, P-3h-2-B, P-3h-3-B, P-3h-4-B, P-3h-5-B, P-3h-6-B, P-3h-7-B, P-3h-8-B, P-3h-9-B, P-3h-10-B, P-3h-11-B, P-3h-1-C, P-3h-2-C, P-3h-3-C, P-3h-4-C, P-3h-6-C, P-3h-7-C, P-3h-8-C, P-3h-9-C, P-3h-10-C, P-3h-11-C, P-6h-1-A, P-6h-2-A, P-6h-3-A, P-6h-4-A, P-6h-5-A, P-6h-6-A, P-6h-7-A, P-6h-8-A, P-6h-9-A, P-6h-10-A, P-6h-11-A, P-6h-1-B, P-6h-2-B, P-6h-3-B, P-6h-4-B, P-6h-5-B, P-6h-6-B, P-6h-7-B, P-6h-8-B, P-6h-9-B, P-6h-10-B, P-6h-11-B, P-6h-1-C, P-6h-2-C, P-6h-3-C, P-6h-4-C, P-6h-5-C, P-6h-6-C, P-6h-7-C, P-6h-8-C, P-6h-9-C, P-6h-10-C, P-6h-11-C, P-12h-1-A, P-12h-2-A, P-12h-3-A, P-12h-4-A, P-12h-5-A, P-12h-6-A, P-12h-7-A, P-12h-8-A, P-12h-9-A, P-12h-10-A, P-12h-11-A, P-12h-1-B, P-12h-2-B, P-12h-3-B, P-12h-4-B, P-12h-5-B, P-12h-6-B, P-12h-7-B, P-12h-8-B, P-12h-9-B, P-12h-10-B, P-12h-11-B, P-12h-1-C, P-12h-2-C, P-12h-3-C, P-12h-6-C, P-12h-7-C, P-12h-8-C, P-12h-9-C, P-12h-10-C, P-12h-11-C. ‘T’ represents total RNA, ‘P’ represents RNA from polysomes fractions, ‘c’ represents RNA from untreated cells, ‘3h’ represents RNA from cells collected 3 h after UVC treatment, ‘6h’ represents RNA from cells collected 6 h after UVC treatment, ‘12h’ represents RNA from cells collected 12 h after UVC treatment. The numbers 1-11 correspond to the each polysomal fraction. The letters A, B and C correspond to the three independent experimental datasets. Keywords = post-transcriptional / translation / nascent protein synthesis / stress response / ribonomics Keywords: ordered

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Project description:BackgroundOnly a small amount of solar ultraviolet C (UV-C) radiation reaches the Earth's surface. This is because of the filtering effects of the stratospheric ozone layer. Artificial UV-C irradiation is used on leaves and fruits to stimulate different biological processes in plants. Grapes are a major fruit crop and are grown in many parts of the world. Research has shown that UV-C irradiation induces the biosynthesis of phenols in grape leaves. However, few studies have analyzed the overall changes in gene expression in grape leaves exposed to UV-C.Methodology/principal findingsIn the present study, transcriptional responses were investigated in grape (Vitis vinifera L.) leaves before and after exposure to UV-C irradiation (6 W·m-2 for 10 min) using an Affymetrix Vitis vinifera (Grape) Genome Array (15,700 transcripts). A total of 5274 differentially expressed probe sets were defined, including 3564 (67.58%) probe sets that appeared at both 6 and 12 h after exposure to UV-C irradiation but not before exposure. A total of 468 (8.87%) probe sets and 1242 (23.55%) probe sets were specifically expressed at these times. The probe sets were associated with a large number of important traits and biological pathways, including cell rescue (i.e., antioxidant enzymes), protein fate (i.e., HSPs), primary and secondary metabolism, and transcription factors. Interestingly, some of the genes involved in secondary metabolism, such as stilbene synthase, responded intensely to irradiation. Some of the MYB and WRKY family transcription factors, such as VvMYBPA1, VvMYB14, VvMYB4, WRKY57-like, and WRKY 65, were also strongly up-regulated (about 100 to 200 fold).ConclusionsUV-C irridiation has an important role in some biology processes, especially cell rescue, protein fate, secondary metabolism, and regulation of transcription.These results opened up ways of exploring the molecular mechanisms underlying the effects of UV-C irradiation on grape leaves and have great implications for further studies.

Dataset Information

Negative regulation of the FOXO3a transcription factor by mTORC2 induces a pro-survival response following exposure to ultraviolet-B irradiation.

Publications

Negative regulation of the FOXO3a transcription factor by mTORC2 induces a pro-survival response following exposure to ultraviolet-B irradiation.

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