title: PP2A regulates the pro-apoptotic activity of FOXO1.
abstract: FOXO1, a member of the evolutionarily conserved forkhead family of transcription factors, regulates expression of a number of genes that play critical roles in cell cycle and apoptosis. A pivotal regulatory mechanism of FOXO is reversible phosphorylation, catalyzed by kinases and phosphatases. Phosphorylation of FOXO1 is associated with 14-3-3 binding and cytosolic localization, whereas dephosphorylated FOXO1 translocates to the nucleus and is transcriptionally active. Experiments were performed to identify the serine/threonine phosphatase that dephosphorylates FOXO1. PP2A inhibitors, okadaic acid and fostriecin, increased FOXO1 phosphorylation in vitro and in cells. Microcystin-agarose pull-downs suggested that a phosphatase binds to FOXO1, and PP2A catalytic subunit was identified in endogenous FOXO1 immunocomplexes, indicating that PP2A is a FOXO1 phosphatase. Purified PP2A interacted directly with FOXO1 and dephosphorylated FOXO1 in vitro. Silencing of PP2A protected FOXO1 from dephosphorylation and delayed FOXO1 nuclear translocation, confirming the physiologic role of PP2A in the regulation of FOXO1 function. Furthermore, inhibition of PP2A phosphatases rescued FOXO1-mediated cell death by regulating the level of the pro-apoptotic protein BIM. We conclude that PP2A is a physiologic phosphatase of FOXO1.
authors.affiliation: Department of Pediatrics, Cancer Biology, , The Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Yan
authors.forename: Viviana A
authors.initials: VA
authors.lastname: Lavin
authors.forename: Leta R
authors.initials: LR
authors.lastname: Moser
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Cui
authors.forename: Cindy
authors.initials: C
authors.lastname: Kanies
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Yang
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D020134:Catalytic Domain / Q000502:physiology; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D019319:Okadaic Acid / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism
chemical_list: D048948:14-3-3 Proteins; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D004791:Enzyme Inhibitors; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019319:Okadaic Acid; D054648:Protein Phosphatase 2