HIF-2α phosphorylation by CK1δ promotes erythropoietin secretion in liver cancer cells under hypoxia.
Hypoxia inducible factor 2 (HIF-2) is a transcriptional activator implicated in the cellular response to hypoxia. Regulation of its inducible subunit, HIF-2α (also known as EPAS1), involves post-translational modifications. Here, we demonstrate that casein kinase 1δ (CK1δ; also known as CSNK1D) phosphorylates HIF-2α at Ser383 and Thr528 in vitro We found that disruption of these phosphorylation sites, and silencing or chemical inhibition of CK1δ, reduced the expression of HIF-2 target genes and the secretion of erythropoietin (EPO) in two hepatic cancer cell lines, Huh7 and HepG2, without affecting the levels of HIF-2α protein expression. Furthermore, when CK1δ-dependent phosphorylation of HIF-2α was inhibited, we observed substantial cytoplasmic mislocalization of HIF-2α, which was reversed upon the addition of the nuclear protein export inhibitor leptomycin B. Taken together, these data suggest that CK1δ enhances EPO secretion from liver cancer cells under hypoxia by modifying HIF-2α and promoting its nuclear accumulation. This modification represents a new mechanism of HIF-2 regulation that might allow HIF isoforms to undertake differing functions.
Laboratory of Biochemistry, Faculty of Medicine, University of Thessaly, Biopolis, Larissa 41500, Greece.
Evanthia
E
Pangou
Laboratory of Biochemistry, Faculty of Medicine, University of Thessaly, Biopolis, Larissa 41500, Greece.
Christina
C
Befani
Laboratory of Biochemistry, Faculty of Medicine, University of Thessaly, Biopolis, Larissa 41500, Greece.
Ilias
I
Mylonis
Protein Chemistry Laboratory, Biomedical Sciences Research Center "Alexander Fleming", Vari 16672, Greece.
Martina
M
Samiotaki
Protein Chemistry Laboratory, Biomedical Sciences Research Center "Alexander Fleming", Vari 16672, Greece.
George
G
Panayotou
Laboratory of Biochemistry, Faculty of Medicine, University of Thessaly, Biopolis, Larissa 41500, Greece.
George
0000-0001-5453-3185
G
Simos
Laboratory of Biochemistry, Faculty of Medicine, University of Thessaly, Biopolis, Larissa 41500, Greece pliakos@med.uth.gr.
Panagiotis
0000-0002-3800-5056
P
Liakos
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D048148:Casein Kinase Idelta / Q000378:metabolism*; D015687:Cell Hypoxia; D002467:Cell Nucleus / Q000378:metabolism; D004921:Erythropoietin / Q000378:metabolism*; D020868:Gene Silencing; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D028884:Karyopherins / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D011485:Protein Binding; D055550:Protein Stability; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D014158:Transcription, Genetic; D051720:Upstream Stimulatory Factors / Q000378:metabolism; D000097606:Exportin 1 Protein; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D048148:Casein Kinase Idelta; D004921:Erythropoietin; D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D051720:Upstream Stimulatory Factors; D000097606:Exportin 1 Protein; D000099162:Endothelial PAS Domain-Containing Protein 1; C497184:USF2 protein, human
CK1; CRM1; EPO; HIF-2; Liver cancer cell; Phosphorylation