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Stabilization of Hypoxia-inducible Factor-1α Protein in Hypoxia Occurs Independently of Mitochondrial Reactive Oxygen Species Production

2010; Elsevier BV; Volume: 285; Issue: 41 Linguagem: Inglês

10.1074/jbc.m110.158485

1083-351X

Yee Liu Chua, Éric Dufour, Emmanuel P. Dassa, Pierre Rustin, Howard T. Jacobs, Cormac T. Taylor, Thilo Hagen,

Mitochondrial Function and Pathology

The transcription factor hypoxia-inducible factor-1α (HIF-1α) is a master regulator of the cellular response to low oxygen. HIF-1α protein accumulates in hypoxia due to inhibition of prolyl hydroxylase enzymes, which under normoxic conditions use molecular oxygen to hydroxylate HIF-1α on two conserved proline residues (Pro402 and Pro564), thus targeting the protein for 26 S proteasome-dependent degradation. A functional mitochondrial electron transport chain is known to be necessary for HIF-1α stabilization in hypoxia. It has been reported that reactive oxygen species (ROS), produced under hypoxia by complex III of the mitochondrial electron transport chain, play a critical role in the stabilization of the HIF-1α protein, possibly by directly inhibiting prolyl hydroxylase enzymes. In contrast, we found that ROS production by complex III is not required for hypoxia-induced HIF-1α stabilization. Thus, reestablishing mitochondrial oxygen consumption in the presence of a complex III inhibitor by using an artificial electron donor to complex IV or by overexpressing Ciona intestinalis alternative oxidase results in HIF-1α protein stabilization in hypoxia. Furthermore, five inhibitors that target different sites of the mitochondrial electron transport chain have similar effects on the HIF-1α protein half-life in hypoxia but vary in their effects on mitochondrial ROS production. Finally, ROS do not regulate prolyl hydroxylase activity directly. We conclude that HIF-1α protein stabilization in hypoxia occurs independently of mitochondrial ROS production. However, mitochondria can modulate the cellular hypoxic response through altered respiratory activity, likely by regulating the cellular oxygen availability. The transcription factor hypoxia-inducible factor-1α (HIF-1α) is a master regulator of the cellular response to low oxygen. HIF-1α protein accumulates in hypoxia due to inhibition of prolyl hydroxylase enzymes, which under normoxic conditions use molecular oxygen to hydroxylate HIF-1α on two conserved proline residues (Pro402 and Pro564), thus targeting the protein for 26 S proteasome-dependent degradation. A functional mitochondrial electron transport chain is known to be necessary for HIF-1α stabilization in hypoxia. It has been reported that reactive oxygen species (ROS), produced under hypoxia by complex III of the mitochondrial electron transport chain, play a critical role in the stabilization of the HIF-1α protein, possibly by directly inhibiting prolyl hydroxylase enzymes. In contrast, we found that ROS production by complex III is not required for hypoxia-induced HIF-1α stabilization. Thus, reestablishing mitochondrial oxygen consumption in the presence of a complex III inhibitor by using an artificial electron donor to complex IV or by overexpressing Ciona intestinalis alternative oxidase results in HIF-1α protein stabilization in hypoxia. Furthermore, five inhibitors that target different sites of the mitochondrial electron transport chain have similar effects on the HIF-1α protein half-life in hypoxia but vary in their effects on mitochondrial ROS production. Finally, ROS do not regulate prolyl hydroxylase activity directly. We conclude that HIF-1α protein stabilization in hypoxia occurs independently of mitochondrial ROS production. However, mitochondria can modulate the cellular hypoxic response through altered respiratory activity, likely by regulating the cellular oxygen availability.