title: Differentiation-inducing factor-1 induces cyclin D1 degradation through the phosphorylation of Thr286 in squamous cell carcinoma.
abstract: Differentiation-inducing factors (DIFs) are morphogens which induce cell differentiation in Dictyostelium. We reported that DIF-1 and DIF-3 inhibit proliferation and induce differentiation in mammalian cells. In this study, we investigated the effect of DIF-1 on oral squamous cell carcinoma cell lines NA and SAS, well differentiated and poorly differentiated cell lines, respectively. Although DIF-1 did not induce the expression of cell differentiation makers in these cell lines, it inhibited the proliferation of NA and SAS in a dose-dependent manner by restricting the cell cycle in the G0/G1 phase. DIF-1 induced cyclin D1 degradation, but this effect was prevented by treatment with lithium chloride and SB216763, the inhibitors of glycogen synthase kinase-3beta (GSK-3beta). Depletion of endogenous GSK-3beta by RNA interference also attenuated the effect of DIF-1 on cyclin D1 degradation. Therefore, we investigated the effect of DIF-1 on GSK-3beta and found that DIF-1 dephosphorylated GSK-3beta on Ser9 and induced the nuclear translocation of GSK-3beta, suggesting that DIF-1 activated GSK-3beta. Then, we examined the effect of DIF-1 on cyclin D1 mutants (Thr286Ala, Thr288Ala, and Thr286/288Ala). We revealed that Thr286Ala and Thr286/288Ala mutants were highly resistant to DIF-1-induced degradation compared with wild-type cyclin D1, indicating that the phosphorylation of Thr286 was critical for cyclin D1 degradation induced by DIF-1. These results suggest that DIF-1 induces degradation of cyclin D1 through the GSK-3beta-mediated phosphorylation of Thr286.
authors.affiliation: Department of Clinical Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Mori
authors.forename: Fumi
authors.initials: F
authors.lastname: Takahashi-Yanaga
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Miwa
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Masato
authors.initials: M
authors.lastname: Hirata
authors.forename: Sachio
authors.initials: S
authors.lastname: Morimoto
authors.forename: Kanemitsu
authors.initials: K
authors.lastname: Shirasuna
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Sasaguri
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006588:Hexanones / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000494:pharmacology / Q000627:therapeutic use*; D009062:Mouth Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D021381:Protein Transport; D034622:RNA Interference; D013912:Threonine / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C490570:Differentiation-inducing factor-1, Dictyostelium; D006588:Hexanones; D006843:Hydrocarbons, Chlorinated; D019938:Cyclin D1; D013912:Threonine; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3