Hydrogen sulfide (H2S), a signaling molecule that elicits profound physiological effects, is a product of mammalian sulfur metabolism and is synthesized at relatively high rates. Since H2S is highly toxic, cells avoid its build-up by an efficient oxidation pathway that is housed in mitochondria and coupled to the energy-generating electron transport chain. The constituent proteins include sulfide-quinone oxidoreductase (SQR), a persulfide dioxygenase (ETHE1) and rhodanese in addition to the well-studied sulfite oxidase that catalyzes the conversion of sulfite to sulfate in the terminal step in the pathway. In red blood cells on the other hand, which exhibit robust H2S production capacity but lack mitochondria and hence the classical route for sulfide oxidation, the mechanism of sulfide clearance is unknown. In this study, we propose to address fundamental gaps in our understanding of the oxygen-dependent steps catalyzed by SQR and ETHE1, which combine to maintain low steady-state levels of H2S (in the 10-30 nM range in most tissues) and to elucidate the role of rhodanese in the sulfide oxidation pathway. We also propose to elucidate the potential role of methemoglobin in sulfide removal in red blood cells. These goals will be realized by addressing the following specific aims. (i) Using a combination of spectroscopic and kinetic methods we will elucidate the reaction mechanisms of human SQR and ETHE1. (ii) We will assess the relative catalytic efficiencies with which rhodanese generates glutathione persulfide, thiosulfate and H2S and elucidate the biochemical differences between two common polymorphic rhodanese variants. (iii) We will elucidate the mechanism of methemoglobin-dependent sulfide oxidation and assess its contribution to sulfide clearance at physiologically relevant concentrations of H2S and methemoglobin. Our studies will address fundamental questions such as how the sulfide oxidation pathway is wired, elucidate the reaction mechanisms of key enzymes that are potentially important pharmaceutical targets for modulating H2S levels and assess a novel and previously unexplored role for human hemoglobin in maintaining low plasma H2S concentrations.

Public Health Relevance

Defects in sulfur metabolism impact human health and hydrogen sulfide (H2S), a newly discovered sulfur metabolite, influences many physiological functions ranging from blood vessel dilation, to neuromodulation and inflammation. Our proposed studies will address how the H2S oxidation pathway is organized and operates and will illuminate a novel and heretofore unconsidered, mechanism by which red blood cells regulate blood H2S levels. Our studies will lay the foundation for designing modulators of the H2S oxidation pathway enzymes and inform therapeutic strategies for conditions associated with their malfunction.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM112455-01
Application #
8784795
Study Section
Special Emphasis Panel (ZRG1-BCMB-D (03))
Program Officer
Barski, Oleg
Project Start
2014-08-01
Project End
2018-07-31
Budget Start
2014-08-01
Budget End
2015-07-31
Support Year
1
Fiscal Year
2014
Total Cost
$294,710
Indirect Cost
$102,210
Name
University of Michigan Ann Arbor
Department
Biochemistry
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Banerjee, Ruma (2018) Introduction to the Thematic Minireview Series: Redox metabolism and signaling. J Biol Chem 293:7488-7489
Filipovic, Milos R; Zivanovic, Jasmina; Alvarez, Beatriz et al. (2018) Chemical Biology of H2S Signaling through Persulfidation. Chem Rev 118:1253-1337
Libiad, Marouane; Motl, Nicole; Akey, David L et al. (2018) Thiosulfate sulfurtransferase-like domain-containing 1 protein interacts with thioredoxin. J Biol Chem 293:2675-2686
Kabil, Omer; Motl, Nicole; Strack, Martin et al. (2018) Mechanism-based inhibition of human persulfide dioxygenase by ?-glutamyl-homocysteinyl-glycine. J Biol Chem 293:12429-12439
Motl, Nicole; Skiba, Meredith A; Kabil, Omer et al. (2017) Structural and biochemical analyses indicate that a bacterial persulfide dioxygenase-rhodanese fusion protein functions in sulfur assimilation. J Biol Chem 292:14026-14038
Yadav, Vinita; Gao, Xing-Huang; Willard, Belinda et al. (2017) Hydrogen sulfide modulates eukaryotic translation initiation factor 2? (eIF2?) phosphorylation status in the integrated stress-response pathway. J Biol Chem 292:13143-13153
Landry, Aaron P; Ballou, David P; Banerjee, Ruma (2017) H2S oxidation by nanodisc-embedded human sulfide quinone oxidoreductase. J Biol Chem 292:11641-11649
Banerjee, Ruma (2017) Catalytic promiscuity and heme-dependent redox regulation of H2S synthesis. Curr Opin Chem Biol 37:115-121
Ruetz, Markus; Kumutima, Jacques; Lewis, Brianne E et al. (2017) A distal ligand mutes the interaction of hydrogen sulfide with human neuroglobin. J Biol Chem 292:6512-6528
Banerjee, Ruma (2017) Introduction to the Thematic Minireview Series: Redox metabolism and signaling. J Biol Chem 292:16802-16803

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