Conserved N-terminal cysteine dioxygenases transduce responses to hypoxia in animals and plants

Abstract

<jats:p>Organisms must respond to hypoxia to preserve oxygen homeostasis. We identify a thiol oxidase, previously assigned as cysteamine (2-aminoethanethiol) dioxygenase (ADO), as a low oxygen affinity (high-<jats:italic>K</jats:italic><jats:sub>m</jats:sub>O<jats:sub>2</jats:sub>) amino-terminal cysteine dioxygenase that transduces the oxygen-regulated stability of proteins by the N-degron pathway in human cells. ADO catalyzes the conversion of amino-terminal cysteine to cysteine sulfinic acid and is related to the plant cysteine oxidases that mediate responses to hypoxia by an identical posttranslational modification. We show in human cells that ADO regulates RGS4/5 (regulator of G protein signaling) N-degron substrates, modulates G protein–coupled calcium ion signals and mitogen-activated protein kinase activity, and that its activity extends to other N-cysteine proteins including the angiogenic cytokine interleukin-32. Identification of a conserved enzymatic oxygen sensor in multicellular eukaryotes opens routes to better understanding and therapeutic targeting of adaptive responses to hypoxia.</jats:p>

Detection, identification, and quantification of oxidative protein modifications

“…Thus, cysteine dioxygenase enzymes, which are common in plants, have been characterized in mammalian tissues, and these nonheme iron-containing enzymes can oxidize N-terminal Cys residues to the sulfinic acid. Interestingly, these enzymes also contain an internal Cys-Tyr thioether cross-link, which markedly enhances the enzymatic activity (195). These enzymes are key regulators of hypoxia responses in both animals and plants (195).…”

“…Interestingly, these enzymes also contain an internal Cys-Tyr thioether cross-link, which markedly enhances the enzymatic activity (195). These enzymes are key regulators of hypoxia responses in both animals and plants (195). Furthermore, there is abundant evidence for enzymatic Cys oxidation occurring by way of redox relays involving proteins with highly-reactive Cys residues, such as peroxiredoxins and STAT3, with initial oxidation of one protein by oxidants such as H 2 O 2 allowing subsequent oxidative transfer to target proteins in a controlled and specific manner.…”

Regulator of Gene Silencing-Calmodulin associates with mRNA granules and the autophagy protein ATG8

“…One observation of interest is that a number of Solanaceae rgsCaM proteins possess amino-terminal cysteine residues (Fig. S5) that are characteristic of proteins regulated by hypoxia through the N-degron pathway (Masson et al, 2019).…”

The plant N‐degron pathways of ubiquitin‐mediated proteolysis

“…The Arg/N‐degron pathway has a hierarchical structure that enzymatically funnels substrates to the N‐recognin by sequential alteration of tertiary to secondary destabilizing Nt‐residues, that are then arginylated to provide an N‐terminus with a primary destabilizing residue (Figure A). Eukaryotic tertiary destabilizing residues Gln and Asn can be converted to Glu and Asp by Nt‐Glu‐ (NTAQ1 (Wang et al )) or Nt‐Asn‐ (NTAN1 (Grigoryev et al )) amidohydrolases, respectively, (represented in Saccharomyces cerevisiae , hereafter yeast, by a single enzyme NTA1 (Baker and Varshavsky )) and Cys to Cys‐sulphinic acid by PLANT CYSTEINE OXIDASE (PCO) enzymes in plants (Weits et al ; White et al ) and an equivalent function in animals, cysteamine (2‐aminoethanethiol) dioxygenase (ADO) (Masson et al ). Secondary destabilizing residues can be Nt‐arginylated by ARGINYL‐tRNA TRANSFERASEs (ATEs) to deliver substrates with Nt‐Arg‐ (Manahan and App ).…”

“…Importantly, the PCOs have K m app (O 2 ) values that are within a physiologically relevant range for response to external or internal oxygen deficit, indicating that they have the capacity to function as oxygen sensors for ecologically important variables, including flooding (White et al ). Following the identification of plant enzymes, an animal ADO enzyme with similar function in regulating mammalian Nt‐Cys substrates was identified (Masson et al ).…”