MammalianEGLNgenes have distinct patterns of mRNA expression and regulation

Abstract

The mammalian EGLN family contains three paralagous genes (EGLN1, EGLN2, and EGLN3) encoding prolyl hydroxylase isoforms that mediate the oxygen-dependent targeting of the transcription factor hypoxia inducible factor alpha to the proteosome. The rat orthologue of EGLN3 (SM-20) exhibits tissue-restricted expression, is induced by growth factors in cultured vascular smooth muscle, and is up-regulated during myogenesis. To determine if all three EGLN genes are coordinately regulated, we examined their mRNA expression in murine tissues and in cultured cells. We now report that the three murine EGLN mRNAs have unique but overlapping patterns of tissue expression. The most striking differences were in the heart, where EGLN3 had its highest levels of expression, and the testis, where EGLN2 was the only isoform expressed. In cultured vascular smooth muscle cells, serum treatment led to up-regulation of EGLN1 and EGLN3, but not EGLN2, and only EGLN3 was superinduced by cyclohexamide. In cultured C2C12 myocytes, EGLN3 was up-regulated during differentiation, whereas EGLN1 and EGLN2 were constitutively expressed. The abundance of EGLN3 mRNA in the heart, its induction by growth factors in vascular smooth muscle, and its regulation during C2C12 differentiation suggest a unique role for EGLN3 and might justify the development of isoformspecific inhibitors.

Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibition: Robust New Target or Another Big Bust for Stroke Therapeutics?

“…Under nonstress conditions, it is highly expressed in the testis, moderately in the liver, and low levels in the heart, brain, and kidney (Lieb et al, 2002). In situ hybridization studies reveal a diffuse expression in the cortex of mice.…”

“…Prolyl hydroxylase-3 also known as EGLN-3 or HIF prolyl hydrolase-1 (HPH-1) is localized in both cytoplasmic and nuclear compartments (Metzen et al, 2003) and highly expressed in the heart and liver and moderately in the brain and kidney (Lieb et al, 2002). These data reflect total RNA averaged over the whole organ, and may not reveal local pockets of elevated expression, particularly in the brain.…”

Prolyl Hydroxylase Domain (PHD) 2 Affects Cell Migration and F-actin Formation via RhoA/Rho-associated Kinase-dependent Cofilin Phosphorylation

“…Although in vitro, all three PHDs are able to hydroxylate HIF-1␣, their in vivo functions seem to differ as indicated by the recently described PHD knock-out models (10 -12). This may be explained partly by their different tissue-specific expression patterns (13)(14)(15). Moreover, PHD2 is deeply involved in the normoxic degradation of HIF-1␣, whereas PHD3 mediates hydroxylation of HIF-1␣ mostly during hypoxia, which is mainly due to the drastic hypoxic induction of PHD3 (16).…”

Developmental regulation of hypoxia-inducible factor 1 and prolyl-hydroxylases in pulmonary vascular smooth muscle cells

“…As O 2 availability determines PHD activity, these enzymes may be the primary oxygen sensors, linking O 2 concentration and HIF-1 protein levels (11). Although the three PHDs are capable of regulating HIF-1, their activity and cellular distribution varies (12)(13)(14). PHD2 likely has the dominant role (15), because ''silencing'' of PHD2 with siRNAs stabilizes and activates HIF-1␣ in normoxia, whereas silencing of PHD1 and PHD3 has no effect on the stability of HIF-1␣.…”