Study summary · research use only
EGF Relays Signals to COP1 and Facilitates FOXO4 Degradation to Promote Tumorigenesis
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
This study (cell line experiments, species not specified) examined how EGF signaling regulates FOXO4 (Forkhead-Box Class O 4) stability via COP9 Signalosome subunit 6 (CSN6) and the E3 ubiquitin ligase COP1. The abstract reports that FOXO4 levels were downregulated in response to EGF treatment alongside elevated CSN6 and COP1 levels, that CSN6 bound and regulated FOXO4 stability by enhancing COP1's E3 ligase activity, and that COP1 directly interacted with FOXO4 through a VP motif to accelerate its ubiquitin-mediated degradation. Metabolomic analysis linked CSN6 expression to serine and glycine production, and FOXO4 was reported to bind and suppress promoters of serine-glycine-one-carbon pathway genes. The authors describe CSN6 and FOXO4 levels as possible prognostic markers in cancer.
Abstract
Forkhead-Box Class O 4 (FOXO4) is involved in critical biological functions, but its response to EGF-PKB/Akt signal regulation is not well characterized. Here, it is reported that FOXO4 levels are downregulated in response to EGF treatment, with concurrent elevation of COP9 Signalosome subunit 6 (CSN6) and E3 ubiquitin ligase constitutive photomorphogenic 1 (COP1) levels. Mechanistic studies show that CSN6 binds and regulates FOXO4 stability through enhancing the E3 ligase activity of COP1, and that COP1 directly interacts with FOXO4 through a VP motif on FOXO4 and accelerates the ubiquitin-mediated degradation of FOXO4. Metabolomic studies demonstrate that CSN6 expression leads to serine and glycine production. It is shown that FOXO4 directly binds and suppresses the promoters of serine-glycine-one-carbon (SGOC) pathway genes, thereby diminishing SGOC metabolism. Evidence shows that CSN6 can regulate FOXO4-mediated SGOC gene expression. Thus, these data suggest a link of CSN6-FOXO4 axis and ser/gly metabolism. Further, it is shown that CSN6-COP1-FOXO4 axis is deregulated in cancer and that the protein expression levels of CSN6 and FOXO4 can serve as prognostic markers for cancers. The results illustrate a pathway regulation of FOXO4-mediated serine/glycine metabolism through the function of CSN6-COP1 axis. Insights into this pathway may be strategically designed for therapeutic intervention in cancers.
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