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A PRDX1-FOXO3 signaling pathway acts as a redox sensor controlling FOXO3 subcellular localization and target gene transactivation

Hopkins, Barbara L (2018) A PRDX1-FOXO3 signaling pathway acts as a redox sensor controlling FOXO3 subcellular localization and target gene transactivation. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

Precision in redox signaling is attained through posttranslational protein modifications such as oxidation of protein thiols. The peroxidase peroxiredoxin 1 (PRDX1) regulates signal transduction through changes in thiol oxidation of its cysteines. We demonstrate here that PRDX1 is a binding partner for the tumor suppressive transcription factor FOXO3 that directly regulates the FOXO3 stress response. Heightened oxidative stress evokes formation of disulfide-bound heterotrimers linking dimeric PRDX1 to monomeric FOXO3. Absence of PRDX1 enhances FOXO3 nuclear localization and transcription that are dependent on the presence of Cys31 or Cys150 within FOXO3. Notably, FOXO3-T32 phosphorylation is constitutively enhanced in these mutants, but nuclear translocation of mutant FOXO3 is restored with PI3K inhibition. Here we show that on H2O2 exposure, transcription of tumor suppressive miRNAs let-7b and let-7c is regulated by FOXO3 or PRDX1 expression levels and that let-7c is a novel target for FOXO3. Conjointly, inhibition of let-7 microRNAs increases let-7-phenotypes in PRDX1-deficient breast cancer cells. Altogether, these data ascertain the existence of an H2O2-sensitive PRDX1-FOXO3 signaling axis that fine tunes FOXO3 activity toward the transcription of gene targets in response to oxidative stress.
The public health significance of this research lies in the fact that elevated levels of oxidative stress in a major cancer risk factor. In breast cancer it has been found that post-menopausal women, who are generally at increased risk for breast cancer development, show an even higher level of oxidative stress markers. Unfortunately, antioxidant therapies have proven ineffectual. If we can gain a deeper understand of how these oxidative stress induced redox-signaling pathways work, it is possible to develop more effective therapies for those at-risk patients for whom therapies fail.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Hopkins, Barbara Lblh63@pitt.edublh63
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorNeumann, Carola Aneumannc@upmc.educan44
Committee MemberLee, Adrian Vleeav@upmc.eduavl10
Committee MemberFinegold, David Ndnf@pitt.edudnf
Committee MemberMinster, Ryan Lrminster@pitt.edurminster
Date: 30 January 2018
Date Type: Publication
Defense Date: 5 September 2017
Approval Date: 30 January 2018
Submission Date: 6 November 2017
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 138
Institution: University of Pittsburgh
Schools and Programs: Graduate School of Public Health > Human Genetics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: FOXO3; PRDX1; breast cancer; let-7; oxidative stress; tumor supressor
Date Deposited: 30 Jan 2018 22:42
Last Modified: 30 Jan 2018 22:42
URI: http://d-scholarship.pitt.edu/id/eprint/33319

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