Mechanism of regulation of the hypoxia-inducible factor-1alpha by the von Hippel-Lindau tumor suppressor protein

Abstract

In normoxic cells the hypoxia-inducible factor-1a (HIF-1a) is rapidly degraded by the ubiquitin-proteasome pathway, and activation of HIF-1a to a functional form requires protein stabilization. Here we show that the product of the von Hippel-Lindau (VHL) tumor suppressor gene mediated ubiquitylation and proteasomal degradation of HIF-1a under normoxic conditions via interaction with the core of the oxygen-dependent degradation domain of HIF-1a. The region of VHL mediating interaction with HIF-1a overlapped with a putative macromolecular binding site observed within the crystal structure of VHL. This motif of VHL also represents a mutational hotspot in tumors, and one of these mutations impaired interaction with HIF-1a and subsequent degradation. Interestingly, the VHL binding site within HIF-1a overlapped with one of the minimal transactivation domains. Protection of HIF-1a against degradation by VHL was a multistep mechanism, including hypoxiainduced nuclear translocation of HIF-1a and an intranuclear hypoxia-dependent signal. VHL was not released from HIF-1a during this process. Finally, stabilization of HIF-1a protein levels per se did not totally bypass the need of the hypoxic signal for generating the transactivation response.

Hypoxia controls CD4+CD25+ regulatory T‐cell homeostasis via hypoxia‐inducible factor‐1α

“…HIF-1 constitutes an oxygen-dependent a-subunit and a constitutively expressed b-subunit that interact through mutual basic helix-loop-helix domains [2]. HIF-1a oxygen-dependent domain undergoes site-specific proline hydroxylation by prolyl hydroxylases, which allows subsequent ubiquitination mediated by the von Hippel-Lindau protein [3][4][5]. In the absence of molecular oxygen, HIF-a hydroxylation is abrogated, leading to its cellular accumulation.…”

6-Mercaptopurine, an activator of Nur77, enhances transcriptional activity of HIF-1α resulting in new vessel formation

“…Whereas HIF-1b, the previously described aryl hydrocarbon receptor nuclear translocator, is quite stable under normoxic conditions, HIF-1a is extremely unstable and is quickly degraded by the ubiquitin-proteasome system (Salceda and Caro, 1997;Huang et al, 1998;Kallio et al, 1999). The tumorsuppressor von Hippel-Lindau (VHL) protein interacts with hydroxylated HIF-1a at Pro564 of HIF-1a in the presence of oxygen, leading to the proteolysis of HIF-1a (Kamura et al, 2000;Tanimoto et al, 2000). Specific HIF prolyl hydroxylases (PHDs) catalyse the hydroxylation of this proline residue in the oxygen-dependent degradation (ODD) domain of HIF-1a (Berra et al, 2003;Cioffi et al, 2003;Erez et al, 2003).…”

The VHL tumor suppressor and HIF: insights from genetic studies in mice

“…pVHL associates with the elongins B and C, cullin2 and Rbx [8][9][10][11][12] and functions as the substrate recognition component of an E3-ubiquitin ligase that ubiquitylates HIF-a. [13][14][15][16][17][18][19] All three HIF a-subunits, HIF-1a, HIF-2a and HIF-3a interact with pVHL. 7,20 This pVHL-HIF-a interaction is highly conserved between species, requires iron-and oxygen-dependent hydroxylation of specific proline residues (Pro402 and Pro564 in human HIF-1a; Pro405 and Pro531 in human HIF-2a) within the oxygen-dependent degradation domain of HIF-a and is necessary for the execution of HIF proteolysis under normoxia.…”