Prolyl-4-Hydroxylase, Transmembrane (P4HTM)

P4HTM belongs to the family of prolyl 4-hydroxylases. This protein is a prolyl hydroxylase that may be involved in the degradation of hypoxia-inducible transcription factors under normoxia. It plays a role in adaptation to hypoxia and may be related to cellular oxygen sensing. Alternatively spliced variants encoding different isoforms have been identified. PH-4, with an aminoterminal EF-hand motif and a carboxyterminal catalytic domain, which was highly expressed in most organs, and-unlike EGLNs which localize to the cytoplasm and nucleus-was associated with the endoplasmic reticulum. Like EGLNs, PH-4 overexpressed in cellular reporter assays suppressed the HIF transactivation activity, dependent on the consensus ODDD proline residues. Suppression of transactivation was correlated with decrease of cellular contents of HIF.