Recombinant PHD3 (EGLN3) protein, FLAG-Tag
Prolyl Hydroxylase Domain-Containing Protein 3 (PHD3) or Egl-9 Family Hypoxia Inducible Factor 3 (EGLN3), also known as PHIF-PH3 or HPH-3, is a prolyl hydroxylase. PHD3 is a cellular oxygen sensor that catalyzes the post-translational formation of 4-hydroxyproline in hypoxia-inducible factor (HIF) alpha proteins under normoxic conditions. It can hydroxylate a specific proline found in each of the oxygen-dependent degradation (ODD) domains (N-terminal, NODD, and C-terminal, CODD) of HIF1A, also HIF2A. PHD3 has a preference for the CODD site for both HIF1A and HIF2A. Hydroxylation on the NODD site by PHD3 appears to require prior hydroxylation on the CODD site, and then hydroxylated HIFs are targeted for proteasomal degradation via the von Hippel-Lindau ubiquitination complex. Under hypoxic conditions, the hydroxylation reaction is attenuated allowing HIFs to escape degradation resulting in their translocation to the nucleus, heterodimerization with HIF1B, and increased expression of hypoxy-inducible genes. PHD3 can also hydroxylate PKM in hypoxia, limiting glycolysis, while under normoxia, hydroxylate and regulates the stability of ADRB2. In cardiomyocytes, it inhibits the anti-apoptotic effect of BCL2 by disrupting the BAX-BCL2 complex. In neurons, it has a NGF-induced proapoptotic effect, probably through regulating CASP3 activity. PHD3 is essential for hypoxic regulation of neutrophilic inflammation. Beside, it plays a crucial role in DNA damage response (DDR) by hydroxylating TELO2, promoting its interaction with ATR which is required for activation of the ATR/CHK1/p53 pathway. Its target proteins are preferentially recognized via a LXXLAP motif.