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Thomas DeCoursey, PhD

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Thomas DeCoursey, PhD

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Professor, Department of Physiology & Biophysics

Rush Medical College

Professor, Department of Physiology & Biophysics

Contact Information

Address: 1750 W. Harrison St., Suite 1245
Chicago, IL 60612
Phone:
(312) 942-3267
Fax:
(312) 942-8711
Email:
thomas_decoursey@rush.edu

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Research Profile

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PhD, University of Cincinnati College of Medicine
BA, McPherson College, Kansas
The properties and biological functions of ion channels are long-term interests of Tom DeCoursey’s laboratory. A major focus in recent years is the voltage-gated proton channel {Table}. Modulation of the voltage-dependence of this channel by pHo and pHi ensures that it opens only when the electrochemical gradient for H+ is outward (in most species). In other words, when the proton channel opens, it extrudes acid from cells. In a long collaboration with Dr. Vladimir V. Cherny and others, the behavior of proton channels has been explored in alveolar epithelial cells and in white blood cells (human neutrophils and eosinophils). Immune cells engulf (phagocytose) bacteria and kill parasites by secreting reactive oxygen species (e.g., ChloroxTM). The enzyme responsible for these heroic actions is NADPH oxidase. This enzyme moves electrons across the cell membrane to form superoxide anion near the invading critters. We measure the electron movement directly as an electrical current. For each electron that leaves, one proton stays in the cell. To prevent massive depolarization as well as acidification, protons exit the cell through proton channels. Without H+ efflux, the killing process would be interrupted prematurely. Fortunately, proton channels are activated, relieving the cell of excess acid {Respiratory Burst figure; cartoon modified to show stoichiometry}, and preventing depolarization. The discovery of proton channels has been a great boon to cells, who until this time had to use other, less efficient means of extruding acid. Identification of proton channel genes in 2006 has transformed the field. More functions are described each year, and structure-function studies are appearing. The channel was shown to be a dimer, with conduction pathway in each protomer. The dimer gates cooperatively - both protomers need to move before either conducts. New genes (eight confirmed, dozens speculated) are appearing at a high rate. The proton channel resists efforts to crystallize it. The first crystal structure was reported in 2014 by Takeshita et al, is likely closed, and is of a chimera with a Voltage-Sensing Phosphatase. James Letts’ valiant efforts to determine the open structure of HV1 (a chimera with KVAP) can be found in his PhD dissertation, which also nicely shows that Asp112 mutants have severely compromised H+ flux! HV1 triggers the flash in bioluminescent dinoflagellates (Smith et al, 2011), which were recently active in Tasmania!
The properties and biological functions of ion channels are long-term interests of the Tom DeCoursey, PhD, laboratory. A major focus in recent years is the voltage-gated proton channel. Modulation of the voltage-dependence of this channel by pHo and pHi ensures that it opens only when the electrochemical gradient for H+ is outward (in most species). In other words, when the proton channel opens, it extrudes acid from cells. In a long collaboration with Vladimir V. Cherny, PhD, and others, the behavior of proton channels has been explored in alveolar epithelial cells and in white blood cells (human neutrophils and eosinophils). Immune cells engulf (phagocytose) bacteria and kill parasites by secreting reactive oxygen species (e.g., ChloroxTM). The enzyme responsible for these heroic actions is NADPH oxidase. This enzyme moves electrons across the cell membrane to form superoxide anion near the invading critters. DeCoursey's lab measures the electron movement directly as an electrical current. For each electron that leaves, one proton stays in the cell. To prevent massive depolarization as well as acidification, protons exit the cell through proton channels. Without H+ efflux, the killing process would be interrupted prematurely. Fortunately, proton channels are activated, relieving the cell of excess acid and preventing depolarization. The discovery of proton channels has been a great boon to cells, which until this time had to use other, less efficient means of extruding acid.

Identification of proton channel genes in 2006 has transformed the field. More functions are described each year, and structure-function studies are appearing. The channel was shown to be a dimer with conduction pathway in each protomer. The dimer gates cooperatively, both protomers need to move before either conducts. New genes (eight confirmed, dozens speculated) are appearing at a high rate. The proton channel resists efforts to crystallize it. The first crystal structure was reported in 2014 by Takeshita et al, is likely closed, and is of a chimera with a voltage-sensing phosphatase. James Letts' valiant efforts to determine the open structure of HV1 (a chimera with KVAP) can be found in his PhD dissertation, which also nicely shows that Asp112 mutants have severely compromised H+ flux.

HV1 triggers the flash in bioluminescent dinoflagellates (Smith et al, 2011), which were recently active in Tasmania.
Complete list of published work on PubMed

Complete list of published work on Scopus

Complete list of published work on ORCID

Select recent publications
1. Rodriguez, J.D., S. Haq, T. Bachvaroff, K.F. Nowak, S.J. Nowak, D. Morgan, V.V. Cherny, M.M. Sapp, S. Bernstein, A. Bolt, T.E. DeCoursey, A.R. Place, and S.M.E. Smith. 2017. Identification of a vacuolar proton channel that triggers the bioluminescent flash in dinoflagellates. PLoS ONE. 12:e0171594. doi: 10.1371/journal.pone.0171594.
2. Thomas, S., V.V. Cherny, D. Morgan, L.R. Artininan, V. Rehder, S.M.E. Smith,and T.E. DeCoursey. 2018. Exotic properties of a voltage-gated proton channel in the snail Helisoma trivolvis. Journal of General Physiology. 150:835-850. [Commentary by León D. Islas 2018. The acid test for pH-dependent gating in cloned H_V1 channels. J. Gen. Physiol. 150:781.]
3. Cherny, V.V., D. Morgan, S. Thomas, S.M.E. Smith, and T.E. DeCoursey. 2018. Histidine¹⁶⁸ is crucial to DpH dependent gating of the human voltage gated proton channel, hH_V1. Journal of General Physiology. 150:851-862.
Reviews:
1. DeCoursey, T.E., D. Morgan, B. Musset, and V.V. Cherny. (2016). Insights into the structure and function of H_V1 from a meta-analysis of mutation studies. Journal of General Physiology. 148:97-118. doi: 10.1085/jgp.20161161. PMID: 27481712. PMCID: PMC4969798. [Invited Review]
2. DeCoursey, T.E. (2016). The intimate and controversial relationship between voltage-gated proton channels and the phagocyte NADPH oxidase. Immunological Reviews. 273:194-218. DOI: 10.1111/imr.12437 .
3. DeCoursey, T.E. (2017). CrossTalk proposal: Proton permeation through H_V1 requires transient protonation of a conserved aspartate in the S1 transmembrane helix. Proton permeation through H_V1 requires transient protonation of a conserved aspartate in the S1 transmembrane helix. Journal of Physiology. 595:6793-6795. [Invited CrossTalk debate].
4. DeCoursey, T.E. (2017). Rebuttal from Thomas E. DeCoursey. Journal of Physiology. 595:6801. doi:10.1113/JP274982. PMID: 29023792.
5. DeCoursey, T.E. (2018). Last Word: The Bulk of the Evidence Supports Transient Protonation of Aspartate¹¹² in hH_V1, but the Answer is Not Yet Written in Stone! Journal of Physiology. https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP274495
6. DeCoursey, T.E. (2018). Voltage and pH sensing by the voltage gated proton channel, H_V1. Journal of the Royal Society Interface. 15: 20180198. PMCID: PMC3899857

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