The oxidoreductase PYROXD1 uses NAD(P)+ as an antioxidant to sustain tRNA ligase activity in pre-tRNA splicing and unfolded protein response

Mol Cell. 2021 Jun 17;81(12):2520-2532.e16. doi: 10.1016/j.molcel.2021.04.007. Epub 2021 Apr 29.

Abstract

The tRNA ligase complex (tRNA-LC) splices precursor tRNAs (pre-tRNA), and Xbp1-mRNA during the unfolded protein response (UPR). In aerobic conditions, a cysteine residue bound to two metal ions in its ancient, catalytic subunit RTCB could make the tRNA-LC susceptible to oxidative inactivation. Here, we confirm this hypothesis and reveal a co-evolutionary association between the tRNA-LC and PYROXD1, a conserved and essential oxidoreductase. We reveal that PYROXD1 preserves the activity of the mammalian tRNA-LC in pre-tRNA splicing and UPR. PYROXD1 binds the tRNA-LC in the presence of NAD(P)H and converts RTCB-bound NAD(P)H into NAD(P)+, a typical oxidative co-enzyme. However, NAD(P)+ here acts as an antioxidant and protects the tRNA-LC from oxidative inactivation, which is dependent on copper ions. Genetic variants of PYROXD1 that cause human myopathies only partially support tRNA-LC activity. Thus, we establish the tRNA-LC as an oxidation-sensitive metalloenzyme, safeguarded by the flavoprotein PYROXD1 through an unexpected redox mechanism.

Keywords: NADH; NADPH; PYROXD1; RtcB; UPR; copper; metalloenzyme; myopathy; oxidative stress; oxidoreductase; pre-tRNA splicing; tRNA ligase complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / physiology
  • Catalytic Domain
  • Female
  • HeLa Cells
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • NAD / metabolism
  • NADP / metabolism
  • Oxidation-Reduction
  • Oxidoreductases / metabolism
  • Oxidoreductases Acting on Sulfur Group Donors / metabolism*
  • Oxidoreductases Acting on Sulfur Group Donors / physiology
  • RNA Ligase (ATP) / chemistry
  • RNA Ligase (ATP) / genetics
  • RNA Ligase (ATP) / metabolism*
  • RNA Splicing / genetics
  • RNA Splicing / physiology
  • RNA, Transfer / metabolism*
  • Unfolded Protein Response / physiology
  • X-Box Binding Protein 1 / metabolism

Substances

  • Antioxidants
  • X-Box Binding Protein 1
  • XBP1 protein, human
  • NAD
  • NADP
  • RNA, Transfer
  • Oxidoreductases
  • Oxidoreductases Acting on Sulfur Group Donors
  • PYROXD1 protein, human
  • RNA Ligase (ATP)