title: Runx2 protein stabilizes hypoxia-inducible factor-1α through competition with von Hippel-Lindau protein (pVHL) and stimulates angiogenesis in growth plate hypertrophic chondrocytes.
abstract: The regulation of hypoxia-inducible factor-1α (HIF-1α) during endochondral bone formation is not fully understood. Here, we investigated the cross-talk between HIF-1α and Runt-related transcription factor 2 (Runx2) in the growth plate. Runx2 caused the accumulation of HIF-1α protein in ATDC5 chondrocytes and HEK293 cells under normoxic conditions. Runx2 also increased the nuclear translocation of HIF-1α when coexpressed in HEK293 cells and interacted with HIF-1α at the oxygen-dependent degradation domain (ODDD). In addition, Runx2 competed with von Hippel-Lindau tumor suppressor protein by directly binding to ODDD-HIF-1α and significantly inhibited the ubiquitination of HIF-1α, even though Runx2 did not change the hydroxylation status of HIF-1α. Furthermore, overexpression of Runx2 resulted in the significant enhancement of vascular endothelial growth factor (VEGF) promoter reporter activity and protein secretion. Runx2 significantly increased angiogenic activity in human umbilical vein endothelial cells in vitro. In wild-type mice, HIF-1α and Runx2 were colocalized in hypertrophic chondrocytes in which the cluster of differentiation 31 (CD31) protein was expressed at embryonic day 15.5 (E15.5). In contrast, the expression of HIF-1α was markedly reduced in areas of CD31 expression in Runx2(-/-) mice. These results suggest that Runx2 stabilizes HIF-1α by binding to ODDD to block the interaction between von Hippel-Lindau protein and HIF-1α. In conclusion, Runx2, HIF-1α, and VEGF may regulate vascular angiogenesis spatially and temporally in the hypertrophic zone of the growth plate during endochondral bone formation.
authors.affiliation: School of Life Sciences and Biotechnology, College of Natural Sciences, Daegu 702-701, South Korea.
authors.forename: Sun-Hee
authors.initials: SH
authors.lastname: Lee
authors.forename: Xiangguo
authors.initials: X
authors.lastname: Che
authors.forename: Jae-Hwan
authors.initials: JH
authors.lastname: Jeong
authors.forename: Je-Yong
authors.initials: JY
authors.lastname: Choi
authors.forename: Young-Joo
authors.initials: YJ
authors.lastname: Lee
authors.forename: Yong-Hee
authors.initials: YH
authors.lastname: Lee
authors.forename: Suk-Chul
authors.initials: SC
authors.lastname: Bae
authors.forename: You-Mie
authors.initials: YM
authors.lastname: Lee
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D006900:Hydroxylation / Q000502:physiology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C493709:RUNX2 protein, human; C493716:Runx2 protein, mouse; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D051794:Von Hippel-Lindau Tumor Suppressor Protein; C497446:VHL protein, human; C494469:VHL protein, mouse