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PHD3 is a transcriptional coactivator of HIF-1? in nucleus pulposus cells independent of the PKM2-JMJD5 axis.

ABSTRACT: The role of prolyl hydroxylase (PHD)-3 as a hypoxia inducible factor (HIF)-1? cofactor is controversial and remains unknown in skeletal tissues. We investigated whether PHD3 controls HIF-1 transcriptional activity in nucleus pulposus (NP) cells through the pyruvate kinase muscle (PKM)-2-Jumonji domain--containing protein (JMJD5) axis. PHD3^-/- mice (12.5 mo old) showed increased incidence of intervertebral disc degeneration with a concomitant decrease in expression of the HIF-1? targets VEGF-A, glucose transporter-1, and lactate dehydrogenase A. PHD3 silencing decreased hypoxic activation of HIF-1? C-terminal transactivation domain (C-TAD), but not HIF-1?-N-terminal-(N)-TAD or HIF-2?-TAD. Moreover, PHD3 suppression in NP cells resulted in decreased HIF-1? enrichment on target promoters and lower expression of select HIF-1 targets. Contrary to other cell types, manipulation of PKM2 and JMJD5 levels had no effect on HIF-1 activity in NP cells. Likewise, stabilization of tetrameric PKM2 by a chemical approach had no effect on PHD3-dependent HIF-1 activity. Coimmunoprecipitation assays showed lack of association between HIF-1? and PKM2 in NP cells. Results support the role of the PHD3 as a cofactor for HIF-1, independent of PKM2-JMJD5.-Schoepflin, Z. R., Silagi, E. S., Shapiro, I. M., Risbud, M. V. PHD3 is a transcriptional coactivator of HIF-1? in nucleus pulposus cells independent of the PKM2-JMJD5 axis.

SUBMITTER: Schoepflin ZR

PROVIDER: S-EPMC5572688 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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PHD3 is a transcriptional coactivator of HIF-1α in nucleus pulposus cells independent of the PKM2-JMJD5 axis.

Schoepflin Zachary R ZR Silagi Elizabeth S ES Shapiro Irving M IM Risbud Makarand V MV

FASEB journal : official publication of the Federation of American Societies for Experimental Biology 20170511 9

The role of prolyl hydroxylase (PHD)-3 as a hypoxia inducible factor (HIF)-1α cofactor is controversial and remains unknown in skeletal tissues. We investigated whether PHD3 controls HIF-1 transcriptional activity in nucleus pulposus (NP) cells through the pyruvate kinase muscle (PKM)-2-Jumonji domain--containing protein (JMJD5) axis. PHD3<sup>-/-</sup> mice (12.5 mo old) showed increased incidence of intervertebral disc degeneration with a concomitant decrease in expression of the HIF-1α target ...[more]

PMID: 28495754

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Project description:The intervertebral disc (IVD) is one of the largest avascular organs in vertebrates. The nucleus pulposus (NP), a highly hydrated and proteoglycan-enriched tissue, forms the inner portion of the IVD. The NP is surrounded by a multi-lamellar fibrocartilaginous structure, the annulus fibrosus (AF). This structure is covered superior and inferior side by cartilaginous endplates (CEP). The NP is a unique tissue within the IVD as it results from the differentiation of notochordal cells, whereas, AF and CEP derive from the sclerotome. The hypoxia inducible factor-1α (HIF-1α) is expressed in NP cells but its function in NP development and homeostasis is largely unknown. We thus conditionally deleted HIF-1α in notochordal cells and investigated how loss of this transcription factor impacts NP formation and homeostasis at E15.5, birth, 1 and 4 months of age, respectively. Histological analysis, cell lineage studies, and TUNEL assay were performed. Morphologic changes of the mutant NP cells were identified as early as E15.5, followed, postnatally, by the progressive disappearance and replacement of the NP with a novel tissue that resembles fibrocartilage. Notably, lineage studies and TUNEL assay unequivocally proved that NP cells did not transdifferentiate into chondrocyte-like cells but they rather underwent massive cell death, and were completely replaced by a cell population belonging to a lineage distinct from the notochordal one. Finally, to evaluate the functional consequences of HIF-1α deletion in the NP, biomechanical testing of mutant IVD was performed. Loss of the NP in mutant mice significantly reduced the IVD biomechanical properties by decreasing its ability to absorb mechanical stress. These findings are similar to the changes usually observed during human IVD degeneration. Our study thus demonstrates that HIF-1α is essential for NP development and homeostasis, and it raises the intriguing possibility that this transcription factor could be involved in IVD degeneration in humans.

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PHD3 is a transcriptional coactivator of HIF-1? in nucleus pulposus cells independent of the PKM2-JMJD5 axis.

Publications

PHD3 is a transcriptional coactivator of HIF-1α in nucleus pulposus cells independent of the PKM2-JMJD5 axis.

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