Research ResourceBiochemistry

Oxygen-dependent changes in binding partners and post-translational modifications regulate the abundance and activity of HIF-1α/2α

See allHide authors and affiliations

Science Signaling  20 Jul 2021:
Vol. 14, Issue 692, eabf6685
DOI: 10.1126/scisignal.abf6685

You are currently viewing the abstract.

View Full Text

Log in to view the full text

Log in through your institution

Log in through your institution

Stimulating and suppressing HIFs

Cells respond and adapt to hypoxia (low oxygen) in part by activating the α subunits of the HIF family of transcription factors. Daly et al. performed proteomics analysis of transfected cells to explore the protein modifications and binding partners for full-length versions of the hypoxia-response subunits HIF-1α and HIF-2α. Their findings, which included a phosphorylated cysteine, protein stability effects, and interactions with mitochondrial proteins, indicate that the oxygen-dependent regulation of HIF activity is more extensive and complex than was previously appreciated. This dataset will help to delineate the selective regulation and signaling mechanisms of these closely related isoforms in fine-tuning the cellular response to hypoxia.

Abstract

Cellular adaptation to low-oxygen environments is mediated in part by the hypoxia-inducible factors (HIFs). Like other transcription factors, the stability and transcriptional activity of HIFs—and consequently, the hypoxic response—are regulated by post-translational modifications (PTMs) and changes in protein-protein interactions. Our current understanding of PTM-mediated regulation of HIFs is primarily based on in vitro protein fragment–based studies typically validated in fragment-expressing cells treated with hypoxia-mimicking compounds. Here, we used immunoprecipitation-based mass spectrometry to characterize the PTMs and binding partners for full-length HIF-1α and HIF-2α under normoxic (21% oxygen) and hypoxic (1% oxygen) conditions. Hypoxia substantially altered the complexity and composition of the HIFα protein interaction networks, particularly for HIF-2α, with the hypoxic networks of both isoforms being enriched for mitochondrial proteins. Moreover, both HIFα isoforms were heavily covalently modified. We identified ~40 PTM sites composed of 13 different types of modification on both HIFα isoforms, including multiple cysteine modifications and an unusual phosphocysteine. More than 80% of the PTMs identified were not previously known and about half exhibited oxygen dependency. We further characterized an evolutionarily conserved phosphorylation of Ser31 in HIF-1α as a regulator of its transcriptional function, and we propose functional roles for Thr406, Thr528, and Ser581 in HIF-2α. These data will help to delineate the different physiological roles of these closely related isoforms in fine-tuning the hypoxic response.

View Full Text

Stay Connected to Science Signaling