FIH Regulates Cellular Metabolism through Hydroxylation of the Deubiquitinase OTUB1

Abstract

The asparagine hydroxylase, factor inhibiting HIF (FIH), confers oxygen-dependence upon the hypoxia-inducible factor (HIF), a master regulator of the cellular adaptive response to hypoxia. Studies investigating whether asparagine hydroxylation is a general regulatory oxygen-dependent modification have identified multiple non-HIF targets for FIH. However, the functional consequences of this outside of the HIF pathway remain unclear. Here, we demonstrate that the deubiquitinase ovarian tumor domain containing ubiquitin aldehyde binding protein 1 (OTUB1) is a substrate for hydroxylation by FIH on N22. Mutation of N22 leads to a profound change in the interaction of OTUB1 with proteins important in cellular metabolism. Furthermore, in cultured cells, overexpression of N22A mutant OTUB1 impairs cellular metabolic processes when compared to wild type. Based on these data, we hypothesize that OTUB1 is a target for functional hydroxylation by FIH. Additionally, we propose that our results provide new insight into the regulation of cellular energy metabolism during hypoxic stress and the potential for targeting hydroxylases for therapeutic benefit.

Hypoxia-dependent regulation of inflammatory pathways in immune cells

“…Another study identified FIH as a second, oxygen-dependent hydroxylase that targets HIF (77,78). Subsequent studies demonstrated that while HIF is clearly the major pathway regulated by hydroxylation, signaling components of other pathways such as NF-κB are also subject to enzymatic hydroxylation, although the functional consequences of hydroxylation for non-HIF targets remains an area under investigation (62)(63)(64)79).…”

“…Subsequent studies demonstrated a broader antiinflammatory effect of pharmacological hydroxylase inhibition in diseases such as ischemic acute kidney injury and sepsis, leading to the conclusion that other mechanisms of therapeutic action may also be involved (65,107). Indeed, recent studies have implicated hydroxylase inhibitors in the suppression of cytokine-activated NF-κB-dependent proinflammatory pathways, which may underpin a more general antiinflammatory effect of these drugs (64). Therefore, while hypoxia-sensitive pathways clearly play a complex and multifaceted role in the regulation of immunity and inflammation, the pharmacological activation of these pathways through the application of hydroxylase inhibitors provides a strong, net antiinflammatory effect in multiple models (Figure 3).…”

Hypoxia and Inflammation in Cancer, Focus on HIF and NF-кB

“…and IκBα [83] as well as an upstream regulator of the NF-κB pathway, OTU dDeubiquitinase, Ubiquitin Aldehyde Binding 1 (OTUB1), as being hydroxylated by FIH [84,85]. Although these novel FIH targets provide promising links to NF-κB and oxygen sensing, with the exception of OTUB1 [85], mutational analysis has been unsuccessful in identifying any functional significance for these modifications [83,86].…”

“…Although these novel FIH targets provide promising links to NF-κB and oxygen sensing, with the exception of OTUB1 [85], mutational analysis has been unsuccessful in identifying any functional significance for these modifications [83,86].…”

“…Although OTUB1 hydroxylation by FIH regulates metabolic processes in the cell [85], a role of OTUB1 in activating the NF-κB pathway under hypoxic conditions has yet to be established. Interestingly, other players in the IL-1β pathway, the ubiquitin ligase enzymes Uve1a and Ubc13, are also targets for hydroxylation [84].…”