The zinc chelator, N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine, increases the level of nonfunctional HIF-1alpha protein in normoxic cells.
The hypoxia-inducible factor-1alpha (HIF-1alpha) subunit is activated in response to lack of oxygen. HIF-1alpha-specific prolyl hydroxylase and factor inhibiting HIF-1alpha (FIH-1) catalyze hydroxylation of the proline and asparagine residues of HIF-1alpha, respectively. The hydroxyproline then interacts with ubiquitin E3 ligase, the von Hippel-Lindau protein, leading to degradation of HIF-1alpha by ubiquitin-dependent proteasomes, while the hydroxylation of the asparagine residue prevents recruitment of the coactivator, cAMP-response element-binding protein (CBP), thereby decreasing the transactivation ability of HIF-1alpha. We found that the Zn-specific chelator, N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), enhances the activity of HIF-1alpha-proline hydroxylase 2 but the level of HIF-1alpha protein does not fall because TPEN also inhibits ubiquitination. Since the Zn chelator does not prevent FIH-1 from hydroxylating the asparagine residue of HIF-1alpha, its presence leads to the accumulation of HIF-1alpha that is both prolyl and asparaginyl hydroxylated and is therefore nonfunctional. In hypoxic cells, TPEN also prevents HIF-1alpha from interacting with CBP, so reducing expression of HIF-1alpha target genes. As a result, Zn chelation causes the accumulation of nonfunctional HIF-1alpha protein in both normoxia and hypoxia.
Choi
Su Mi
SM
Department of Life Science, University of Seoul, 90 Cheonnong-dong, Tongdaemun-gu, Seoul 130-743, Republic of Korea.
Choi
Kyung-Ok
KO
Lee
Naery
N
Oh
Myoungsuk
M
Park
Hyunsung
H
D015687:Cell Hypoxia; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D049308:Dioxygenases / Q000378:metabolism; D005029:Ethylenediamines / Q000494:pharmacology*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D006899:Mixed Function Oxygenases; D011393:Procollagen-Proline Dioxygenase / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
D002614:Chelating Agents; D017362:Cyclic AMP Response Element-Binding Protein; D005029:Ethylenediamines; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012097:Repressor Proteins; D014157:Transcription Factors; D025801:Ubiquitin; D006899:Mixed Function Oxygenases; D049308:Dioxygenases; C439790:HIF1AN protein, human; C490190:EGLN1 protein, human; D011393:Procollagen-Proline Dioxygenase; C488894:EGLN3 protein, human; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine