title: FoxK2 is required for cellular proliferation and survival.
abstract: FoxK2 is a forkhead transcription factor expressed ubiquitously in the developing murine central nervous system. Here we investigated the role of FoxK2 in vitro and focused on proliferation and cellular survival. Knockdown of FoxK2 results in a decrease in BrdU incorporation and H3 phosphorylation, suggesting attenuation of proliferation. In the absence of growth factors, FoxK2 knockdown results in a dramatic increase in caspase 3 activity and propidium iodide positive cells, indicative of cell death. Additionally, knockdown of FoxK2 results in an increase in the mRNA of Gadd45α, Gadd45γ, as well as an increase in the phosphorylation of the mTOR dependent kinase p70S6K. Rapamycin treatment completely blocked the increase in p70S6K and synergistically potentiated the decrease in H3 phosphorylation upon FoxK2 knockdown. To gain more insight into the proapoptotic effects upon FoxK2 knockdown we screened for changes in Bcl2 genes. Upon FoxK2 knockdown both Puma and Noxa were significantly upregulated. Both genes were not inhibited by rapamycin treatment, instead rapamycin increased Noxa mRNA. FoxK2 requirement in cellular survival is further emphasized by the fact that resistance to TGFβ-induced cell death was greatly diminished after FoxK2 knockdown. Overall our data suggest FoxK2 is required for proliferation and survival, that mTOR is part of a feedback loop partly compensating for FoxK2 loss, possibly by upregulating Gadd45s, whereas cell death upon FoxK2 loss is induced in a Bcl2 dependent manner via Puma and Noxa.
authors.affiliation: Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Lars P
authors.initials: LP
authors.lastname: van der Heide
authors.forename: Patrick J E C
authors.initials: PJ
authors.lastname: Wijchers
authors.forename: Lars
authors.initials: L
authors.lastname: von Oerthel
authors.forename: J Peter H
authors.initials: JP
authors.lastname: Burbach
authors.forename: Marco F M
authors.initials: MF
authors.lastname: Hoekman
authors.forename: Marten P
authors.initials: MP
authors.lastname: Smidt
mesh_terms: D000818:Animals; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D041681:NIH 3T3 Cells; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D015203:Reproducibility of Results; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D000097642:GADD45 Proteins
chemical_list: D051858:Forkhead Transcription Factors; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D016212:Transforming Growth Factor beta; D000097642:GADD45 Proteins; C000596673:FoxK2 protein, mouse