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AP-2alpha: a regulator of EGF receptor signaling and proliferation in skin epidermis.

ABSTRACT: AP-2 transcription factors have been implicated in epidermal biology, but their functional significance has remained elusive. Using conditional knockout technology, we show that AP-2alpha is essential for governing the balance between growth and differentiation in epidermis. In vivo, epidermis lacking AP-2alpha exhibits elevated expression of the epidermal growth factor receptor (EGFR) in the differentiating layers, resulting in hyperproliferation when the receptors are activated. Chromatin immunoprecipitation and promoter activity assays identify EGFR as a direct target gene for AP-2alpha repression, and, in the absence of AP-2alpha, this is manifested primarily in excessive EGF-dependent phosphoinositol-3 kinase/Akt activity. Together, our findings unveil a hitherto unrecognized repressive role for AP-2alpha in governing EGFR gene transcription as cells exit the basal layer and withdraw from the cell cycle. These results provide insights into why elevated AP-2alpha levels are often associated with terminal differentiation and why tumor cells often display reduced AP-2alpha and elevated EGFR proteins.

SUBMITTER: Wang X

PROVIDER: S-EPMC2063650 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Opposing Effects of EGF Receptor Signaling on Proliferation and Differentiation Initiated by EGF or TSH/EGF Receptor Transactivation.

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| S-EPMC2172819 | biostudies-other

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| S-EPMC6200932 | biostudies-literature

AP-2alpha regulates migration of GN-11 neurons via a specific genetic programme involving the Axl receptor tyrosine kinase.

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Project description:Previously, we found that bombesin receptor subtype 3 (BRS-3) significantly increased in an ozone-stressed airway hyperresponsiveness animal model and resulted in induced wound repair and protection from acute lung injury. In the present study, we determined molecular mechanisms of BRS-3 regulation in human BECs (bronchial epithelial cells) in response to ozone stress. Ten oligonucleotide probes corresponding to various regions of the BRS-3 promoter were used in EMSA (electrophoretic mobilityshift assays). Four were found to have an enhanced mobility shift with extracts from ozone-stressed cells. On the basis of the assay of mutated probes binding with extracts and antibody supershift, they were verified as MTF-1 (metal-regulatory-element-binding transcription factor-1), PPARalpha (peroxisome-proliferator-activated receptor alpha), AP-2alpha (activator protein 2alpha) and HSF-1 (heat-shock factor 1). Next, ChIP (chromatin immunoprecipitation) assay, site-directed mutagenesis technology and antisense oligonucleotide technology were used to observe these transcription factors associated with the BRS-3 promoter. Only AP-2alpha and PPARalpha increased ozone-inducible DNA binding on the BRS-3 promoter and BRS-3 expression. The time courses of AP-2alpha and PPARalpha activation, followed by BRS-3 expression, were also examined. It was shown that ozone-inducible BRS-3 expression and AP-2alpha- and PPARalpha-binding activity correlated over a 48 h period. The translocation of PPARalpha was observed by immunofluorescence assay, which showed that PPARalpha nuclear translocation increased after ozone exposure. Our data suggest that AP-2alpha and PPARalpha may be especially involved in this ozone-inducible up-regulation mechanism of BRS-3 expression.

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Transcriptional interpretation of the EGF receptor signaling gradient.

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| S-EPMC3277169 | biostudies-literature

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