ERK1/2 phosphorylates HIF-2α and regulates its activity by controlling its CRM1-dependent nuclear shuttling

Hypoxia-inducible factor 2 (HIF-2) is a principal component of the cellular response to oxygen deprivation (hypoxia). Its inducible subunit, HIF-2 alpha (also known as EPAS1), is controlled by oxygen-dependent as well as oxygen-independent mechanisms, such as phosphorylation. We show here that HIF-2 alpha is phosphorylated under hypoxia (1% O-2) by extracellular signal-regulated protein kinases 1 and 2 (ERK1/2; also known as MAPK3 and MAPK1, respectively) at serine residue 672, as identified by in vitro phosphorylation assays. Mutation of this site to an alanine residue or inhibition of the ERK1/2 pathway decreases HIF-2 transcriptional activity and causes HIF-2 alpha to mislocalize to the cytoplasm without changing its protein expression levels. Localization, reporter gene and immunoprecipitation experiments further show that HIF-2 alpha associates with the exportin chromosomal maintenance 1 (CRM1, also known as XPO1) in a phosphorylation-sensitive manner and identify two critical leucine residues as part of an atypical CRM1-dependent nuclear export signal (NES) neighboring serine 672. Inhibition of CRM1 or mutation of these residues restores nuclear accumulation and activity of HIF-2 alpha lacking the ERK1/2-mediated modification. In summary, we reveal a novel regulatory mechanism of HIF-2, involving ERK1/2-dependent phosphorylation of HIF-2 alpha, which controls its nucleocytoplasmic shuttling and the HIF-2 transcriptional activity. This article has an associated First Person interview with the first author of the paper.