LABORATORY OF TOM DeCOURSEY

Department of Molecular Biophysics & Physiology

labThe 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 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, 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.



Other Items of Interest: Recent International Conferences 

Telluride Workshop on Proton Transport and Solvation in Biology and Models Systems, August, 2007proton-2007
 T   E   L   L   U   R   I   D   E   PIX

Sokendai International Symposium: Electrochemical Signalling by Membrane Proteins:  Biodiversity and Principle.
Okazaki Conference Center, National Institutes of Natural Sciences at Okazaki in Aichi Prefecture, Japan, March, 2007
Pictures:  Conferees  trying  to  sit  on  the  floor  during  banquets


Gordon Conference on NOX Family NADPH Oxidases in Les Diablerets, Switzerland, October 15-20, 2006
P I C T U R E S - O F -  A - T R I P - T O - A - G L A C I E R - T H E - A R E A - & - C O N F E R E E S

Group photo [1.9 Mbytes!] of the PHAGOCYTE WORKSHOP at the European Society for Clinical Investigation meeting in Praha, Czech Republic, March, 2006

"Proton Conduction in Diverse Media" a conference held at Fitzwilliam College, Cambridge, UK, April, 2005

Proton Solvation and Transport in Chemistry, Biology, and Materials Science: 200 Years After Grotthuss
a workshop sponsored by the Office of Basic Energy Sciences of the United States Department of Energy (DOE), June 25-28, 2006 in Washington, DC

"Proton Conduction in Diverse Media" a conference held at Fitzwilliam College, Cambridge, UK, April, 2005

Visiting David Colquhoun & Family (Andrew & Margaret) (600 kB) to give a seminar at University College London, April, 2005.

Check out David's web page - for a real treat, see his "Politics" page!
For Sports fans, see Andrew Colquhoun's web site - CRICKET!


Telluride Proton Channel Conference, August, 2004
 proton-2004
A few pix: a  b  c  d  e  f  g  h  i  j  k  l  m  (I apologize to those not pictured - my camera did not take always take a picture when I pressed the button).
What's that spell???  (thanks to Noam Agmon)


Photos from the Nobel Symposium on Membrane Proteins: Structure, Function, and Assembly, Stockholm, Sweden. August 22-24, 2003.  Congratulations to Peter Agre and Rod MacKinnon!
(Thanks to Bob Gennis and Gunnar von Heijne for the photos!)


Photos from Moscow, June, 2002: International Conference on Membrane Bioelectrochemistry
in honor of Yuri Chizmadzhev, Frumkin Institute of Electrochemistry Mirsky, Ermakov, 3-Ds, Sokolov, Revelers, Feasters,Kremlin, RedSquare

PHOTOS from Symposium on cardiac and skeletal electrophysiology:
A tribute to Professor Otto F. Hutter
Glasgow University, Scotland, May, 2002

Photos from the First International Proton Channel Conference in Villars, Switzerland, September, 2001! 
Lydia Henderson and Tom DeCoursey calmly discussing whether gp91phox is a proton channel - photo courtesy of Mel Okamura, four participants engrossed in discussion (Hu Xiao Wen, Lydia Henderson, Tom DeCoursey, and Erzebet Ligeti -photo courtesy of Roger C. Thomas), participants exhibiting single-minded purpose (l-r, back row: R.D. Vaughan-Jones, R.W. Meech, A. Maturana, K.H. Krause, B. Banfi (hidden), L.A. Pinto, l-r, front row: T.A. Cross, G. Bueldt, N. Demaurex), a typical meal, the group at Chillon Castle, at the H.R. Giger museum in Gruyeres, Larry and Maria Pinto y mi esposa Carolyn trying to fit into a Swiss car}


The Lab and Environs
Boris Musset from Marburg is our latest addition. He lives in a lakefront high-rise in the sky!  Deri Morgan, Ph.D. joined the lab in 2001. Claudia Eder visited in spring, 2002 (Claudia is below, Sue is above).
Here is the invaluable Tatiana Iastrebova in situ advising Dr. Cherny on electrode manufacturing techniques and in a less formal setting.
Former summer student researcherAudrey DeCoursey, now in Portland.  Audrey's avocation is entering beauty pageants (aka scholarship contests).  She was an actual Miss Portland contestant, and won the Mrs. Portland Mercury 2003 title, in part for her her talent "Demystifying the Citric Acid Cycle" performed with backup dancers  Bumpie and Pumpie who reenacted the reactions.  Here is our other daughter, Jillian.
Fellow advocates of phagocytes are Larry Thomas, Wei Xu, and Julie Murphy & Neeta Shenoy.
Bonus coverage:  a view of Seattle by bicycle (Mark S. Shapiro, Ph.D., tour-guide, now a Texan).
Life in the Department of Molecular Biophysics and Physiology would be impossible without Glenda Keaton-Mahone, Lucille Vaughn, and Ardessa Perkins.
Here is Tom expounding on the PROTON using a classical Pauling-esque marshmallow diagram (courtesy of daughter Jillian when in formative years).
Tom's c.v. (PDF)
COS version curriculum vitae

Resources for Protonophiles
Antony Crofts has a nice discussion of proton conduction
Wolfgang Junge has some cool animations of the proton ATP synthase
Here is a useful nomogram showing the half-life of the superoxide anion before spontaneous disproportionation
(courtesy of Ricardo Murphy)
The Ukraine has a stamp showing the PROTON rocket.


Dante's Divine Comedy
United States Constitution (a little-known document these days)
To see a European view of American "ethics" check out David Colquhoun's awesome web site!


Selected Recent Publications

(OK, OK - ALL recent publications!)
Some PDF files require an online subscription to the journal. 
I am always happy to send reprints, especially useful for papers with color figures.


DeCoursey, T.E., and V.V. Cherny.  (2007).  Pharmacology of voltage-gated proton channels.  Current Pharmaceutical Design. 13:2406-2420.  {journal link}

 {We review the pharmacology of proton channels;  in a word, Zinc!}

DeCoursey, T.E.  (2007).  Electrophysiology of the phagocyte respiratory burst.  Focus on "Large-conductance calcium-activated potassium channel activity is absent in human and mouse neutrophils and is not required for innate immunity" American Journal of Physiology: Cell Physiology. 293:C30-C32.  {pdf}

 {This briefly introduces and provides the context for the study:  Essin, K., B. Salanova, R. Kettritz, M. Sausbier, F.C. Luft, D. Kraus, E. Bohn, I.B. Autenrieth, A. Peschel, P. Ruth, and M. Gollasch.  (2007).  Large-conductance calcium-activated potassium channel activity is absent in human and mouse neutrophils and is not required for innate immunity. Am J Physiol Cell Physiol 293 C45-C54.  Essin and colleagues thoroughly evaluated the "BK hypothesis of Ahluwalia et al (2004) and found no evidence to support it.  Among new tests (cf. Femling et al (2006) below) they used BK channel KO mice, and found their neutrophils normal in every respect, with no evidence for BK channel expression or function.}


Morgan, D., V.V. Cherny, A. Finnegan, J. Bollinger, M.H. Gelb, and T.E. DeCoursey.  (2007).  Sustained activation of proton channels and NADPH oxidase in human eosinophils and murine granulocytes requires PKC but not cPLA2a activity.  Journal of Physiology.  579:327-344. {pdf}.

 {We test and discard the prevailing hypothsesis that proton channels are activated by arachidonic acid (AA) produced by cPLA2a. Specific blockers have no effect, nor is the response changed in knockout mice.  However, PKC inhibtors prevent activation of NADPH oxidase and H channels, and can reverse their activation.  Most surprisingly, part of the effect of AA is sensitive to PKC inhibitors; hence AA activates PKC, not vice versa!}
DeCoursey, T.E.  (2006).  The pros and cons of open peer review Should authors be told who their reviewers are?  Nature  {Invited online commentary.  Posted 14 June, 2006} 
 {I propose that manuscript reviewers' identities should be printed when a paper is published, to increase the accountability of reviewers.}

Femling, J.K., V.V. Cherny, D. Morgan, B. Rada, A.P. Davis, G. Czirják, P. Enyedi, S.K. England, J.G. Moreland, E. Ligeti, W.M. Nauseef, and T.E. DeCoursey. (2006).  The antibacterial activity of human neutrophils and eosinophils requires proton channels but not BK channels. Journal of General Physiology. 127:659-672. {pdf}

{In a full investigation of the topic raised in the Science STKE Perspective below, we cannot reproduce any of the main conclusions of Ahluwalia et al, 2004 (Nature 427:853-858).  There are no BK currents, nor is the BK protein expressed in human neutrophils. BK inhibitors have no effect on currents nor any functional behavior of neutrophils or eosinophils. IbTX has no effect on the ability of neutrophils to kill bacteria.   However, H2O2 measurements reaffirm that proton channels are necessary for sustained NADPH oxidase activity.}
Murphy, R., and T.E. DeCoursey.  (2006).  Charge compensation in phagocytes. Biochimica et Biophysica Acta. 1757:996-1011.

{After saying for years "charge compensation by proton channels is necessary to keep the electrogenic NADPH oxidase working," we realize that in addition to compensating charge  (to balance the electron flux) proton flux performs several additional necessary functions during the respiratory burst:  (1) it prevents large pH excusrions in the cell and phagosome, (2) it minimizes osmotic consequences, and (3) protons are necessary substrates to produce reactive oxygen species.  Thus, even if charge compensation were not necessary, proton flux would still be required.  A mathematical model shows that other conductances can contribute at most ~5% to charge compensation in human neutrophils and eosinophils.}
DeCoursey, T.E.  (2006).  It’s difficult to publish contradictory findings.  Nature.  439:784.
 {I gripe about the difficulty in publishing "negative" or "contradictory" results, despite their obvious importance to scientific progress.}
Morgan, D., V.V. Cherny, R. Murphy, B.Z. Katz, and T.E. DeCoursey.  (2005).  The pH dependence of NADPH oxidase in human eosinophils.  Journal of Physiology.  569:419-431. {pdf}.

{NADPH oxidase is strongly inhibited above or below pHi 7.5, but is not affected by pHo.  Surprisingly, electron current in inside-out patches (reflecting the turnover of the enzyme per se) is only weakly sensitive to pHi.  Evidently a step in assembly or deactivation of the NADPH oxidase complex accounts for the pH sensitivity in intact cells.}

DeCoursey, T.E., and E. Ligeti.  (2005).  Regulation and termination of NADPH oxidase activity.  Cellular and Molecular Life Sciences. 62:2173-2193. {Review}

 {We examine the question of what turns off NADPH oxidase after the respiratory burst, and discover that we do not know the answer.}

Murphy, R., V.V. Cherny, D. Morgan, and T.E. DeCoursey.  (2005).  Voltage-gated proton channels help regulate pHi in rat alveolar epithelium.  American Journal of Physiology - Lung Cellular and Molecular Physiology.  288:L398-L408. {pdf}

{Proton channels help restore pHi after acid loading alveolar epithelial cells.  This is the first demonstrated function for proton channels in the mammalian cells first found to express proton channels (1991)}
DeCoursey, T.E.  (2004).  During the respiratory burst, do phagocytes need proton channels or potassium channels or both? Science's STKE.  2004: pe21. {Perspective on Ion Channels in Phagocytes-pdf}.
{This Perspective critiques a recent paper by the Segal group (Ahluwalia et al, 2004. Nature 427:853-858) which reports that maxi-K channels are the only ion channels in PMA-activated neutrophils and eosinophils, and hence perform all channel-mediated tasks.  Other labs (including ours) do not see these currents, but see proton currents instead.  K+ flux may serve a useful function, but we feel that proton efflux is the main charge compensation mechanism.}

DeCoursey, T.E.  (2003).  Interactions between NADPH oxidase and voltage-gated proton channels: Why electron transport depends on proton transport. FEBS Letters. 555:57-61.  {Summary, Full text + links, pdf}.
 {The physiological interaction between NADPH oxidase and voltage-gated proton channels in phagocytes is reviewed.  A putative electron pathway through NADPH oxidase is discussed, and speculations about the rate-limiting steps at different voltages are presented.}
Cherny, V.V., R. Murphy, V. Sokolov, R.A. Levis, and T.E. DeCoursey.  (2003).  Properties of single voltage-gated proton channels in human eosinophils estimated by noise analysis and direct measurement.  Journal of General Physiology.  121:615-628. {Abstract, FullText, pdf}
 {We determine the conductance of a single proton channel.  We claim the world's smallest directly-measured single-channel currents (7-16 fA).  Noise analysis provides more surprises!}
Morgan, D. V.V. Cherny, R. Murphy, W. Xu, L.L. Thomas, and T.E. DeCoursey.  (2003). Temperature dependence of NADPH oxidase in human eosinophils. Journal of Physiology. {Abstract, pdf}
{The temperature dependence of NADPH oxidase activity is determined.  The intrinsic Ea of electron flux is low (only 14 kcal/mol), but that of the steady-state enzyme activity is much greater (25 kcal/mol), evidently due to strongly temperature-sensitive assembly of the oxidase complex.  More NADPH oxidase complexes assemble at body temperature.}
DeCoursey, T.E., D. Morgan, and V.V. Cherny.  (2003).The voltage dependence of NADPH oxidase reveals why phagocytes need proton channels.  Nature.  422:531-534. {pdf}
 {The voltage dependence of NADPH oxidase activity (electron current) is determined.  Enzyme activity is abolished by extreme depolarization of the cell membrane.  Unexpectedly strong rectification of the electron current-voltage curve resolves the decade-long mystery of apparent discrepancies between the [Zn2+] that inhibits proton channels vs. that which inhibits NADPH oxidase activity (superoxide production). }

DeCoursey, T.E.  (2003). Voltage-gated Proton Channels and Other Proton Transfer Pathways. Physiological Reviews. 83:475-579.

(free pdf download, 2.1 mBytes, lots of color pix)
{Voltage-gated proton channels are reviewed, along with other proton-conducting molecules for comparison.
Valuable prizes will be awarded to those who can prove that they have read the entire review.}

Morgan, D., and T.E. DeCoursey.  (2003).  Diversity of voltage-gated proton channels.  Frontiers in Bioscience.  8:s1266-s1279.{abstract, pdf-requires subscription}

{An abridged version of the big review.  This is part of a special Proton Transport issue of this online journal.}

Schilling, T., A. Gratopp, T.E. DeCoursey, and C. Eder.  (2002).  Voltage-activated  proton currents in human lymphocytes. Journal of Physiology.  545:93-105. {Abstract, full text, pdf}

{More than 700 papers had been published on ion channels in lymphocytes before we finally showed that they have proton channels too!}

DeCoursey, T.E., D. Morgan, and V.V. Cherny.  (2002).  The gp91phox component of NADPH oxidase is not a voltage-gated proton channel. Journal of General Physiology.  120:773-779. {Abstract, full text, pdf}

{We summarize the arguments against the hypothesis that one component of NADPH oxidase functions as a proton channel.}

Morgan, D. V.V. Cherny, M.O. Price, M.C. Dinauer, and T.E. DeCoursey.  (2002).  Absence of proton channels in COS-7 cells expressing functional NADPH oxidase components. Journal of General Physiology. 119:571-580.  {pdf}

{This paper counters arguments raised against the paper listed next.  We show that cells that lack endogenous proton channels still lack them when transfected with gp91phox and other components of NADPH oxidase. Therefore, gp91phox is not a proton channel in phagocytes.}

DeCoursey, T.E., V.V. Cherny, D. Morgan, B.Z. Katz, M.C. Dinauer.  (2001). The gp91phox component of NADPH oxidase is not the voltage-gated proton channel in phagocytes, but it helps. Journal of Biological Chemistry. (Accelerated Publication) 276:36063-36066.

{Identical proton currents are found in control PLB-985 cells, gp91phox knock-outs (and re-transfectants) and in human CGD phagocytes that lack gp91phox expression.  Furthermore, stimulation with PMA increases the proton conductance identically in all cells.  Therefore, gp91phox is not a proton channel in phagocytes.}

DeCoursey, T.E., V.V. Cherny, A.G. DeCoursey, W. Xu and Thomas, L.L. (2001). Interactions between NADPH oxidase-related proton and electron currents in human eosinophils. Journal of Physiology.  535:767-781. {pdf}

{Human eosinophils are shown to have thrice larger electron currents than neutrophils, consistent with their higher rate of superoxide production.  We present evidence that there is a single type of proton channel before and after stimulation with PMA, and that the reported enhanced Zn2+ sensitivity of proton channels in activated cells is an artifact.}

Cherny, V.V., L.M. Henderson, W. Xu, L.L. Thomas and T.E. DeCoursey.  (2001).  Activation of NADPH oxidase-related proton and electron currents in human eosinophils by arachidonic acid.  Journal of Physiology. 535:783-794. {pdf}

{Arachidonic acid enhances proton channel gating similarly to PMA.  The data are mostly consistent with the proposal by Henderson et al (1993) that AA is the final step in the signaling pathwys that activate both NADPH oxidase and proton channels.}

Cherny, V.V., L.L. Thomas and T.E. DeCoursey.  (2001).  Voltage-gated proton currents in human basophils.  Biologicheskie Membrany 6:458-465.

{Human basophils are found to have huge proton currents like eosinophils (which have the highest expression of any cell).  This result is surprising, because proton channels compensate for electron flux therough NADPH oxidase , which is essentially absent in basophils.}

Eder, C., and T.E. DeCoursey.  (2001).  Voltage-gated proton channels in microglia.  Progress in Neurobiology. 64:277-305. {REVIEW}

{We review the properties of proton chanels in all cells, but focus on special roles in microglia.}
Selected papers published in the previous millenium

Schilling T, Quandt FN, Cherny VV, Zhou W, Heinemann U, DeCoursey TE, Eder C (2000) Upregulation of Kv1.3 K+ channels in microglia deactivated by TGF-b. Am J Physiol Cell Physiol 279:C1123-C1134. {abstract, PDF}

DeCoursey, T.E., V.V. Cherny, W. Zhou, and L.L. Thomas.  (2000).  Simultaneous activation of NADPH oxidase-related proton and electron currents in human neutrophils.  Proceedings of the National Academy of Sciences, U.S.A. 97:6885-6889. {abstract, PDF}

DeCoursey, T.E., and V.V. Cherny.  (2000).  Common themes and problems of bioenergetics and voltage-gated proton channels. Biochimica Biophysica Acta 1458:104-119.{abstract, full text}

The following two papers are my MILLENIUM BOOKENDS:
  The LAST paper published in the LAST issue of The Journal of General Physiology in the 20th Century
and the FIRST paper in the FIRST issue of the American Journal of Physiology: Cell Physiology in the 21st Century!

DeCoursey, T.E.  (2000).  Hypothesis: do voltage-gated H+ channels in alveolar epithelial cells contribute to CO2 elimination by the lung? Amer. J. Physiol. Cell Physiol. 278:C1-C10. {abstract, full-text, PDF} This figure {69 kb, taken from this paper, with permission} illustrates the hypothetical involvement of proton channels in extruding CO2.

Cherny, V.V., and T.E. DeCoursey.  (1999).  pH dependent inhibition of voltage-gated H+ currents in rat alveolar epithelial cells by Zn2+ and other divalent cations. J. Gen. Physiol. 114:819-838. {abstract, fulltext, PDF}

DeCoursey, T.E. and V.V. Cherny.  (1998).  Temperature dependence of voltage-gated H+ currents in human neutrophils, rat alveolar epithelial cells, and mammalian phagocytes.  J. Gen. Physiol. 112:503-522. {abstract//fulltext//PDF}

DeCoursey, T.E. (1998). Four varieties of voltage-gated proton channels. Frontiers in Bioscience. 3:d477-d482. {full-length review}

Captain Proton web site 
Zhou, W., F.S. Cayabyab, P.S. Pennefather, L.C. Schlichter and T.E. DeCoursey. (1998). HERG-like K+ channels in microglia. J. Gen. Physiol. 111:781-794. {abstract//fulltext//PDF}

Pennefather P.S., W. Zhou and T.E. DeCoursey. (1998). Idiosyncratic gating of HERG-like K+ channels in microglia. J. Gen. Physiol. 111:795-805. {abstract//fulltext/PDF}

DeCoursey, T.E. and V.V. Cherny. (1997). Deuterium isotope effects on permeation and gating of proton channels in rat alveolar epithelium. J. Gen. Physiol. 109:415-434. {abstract//fulltext//PDF}

DeCoursey, T.E., S.Y. Kim, M.R. Silver and F.N. Quandt. (1996). III. Ion channel expression in PMA-differentiated human THP-1 macrophages. J. Membrane Biol. 152:141-157. {abstract}

Cherny, V.V., V.S. Markin and T.E. DeCoursey. (1995). The voltage-activated hydrogen ion conductance in rat alveolar epithelial cells is determined by the pH gradient. J. Gen. Physiol. 105:861-896. {abstract}
DeCoursey, T.E. and V.V. Cherny.(1995).Voltage-activated proton currents in membrane patches of rat alveolar epithelial cells.J. Physiol.489:299-307. {abstract}

DeCoursey, T.E. and V.V. Cherny. (1994). Voltage-activated hydrogen ion currents. J Membrane Biol. 141:203-223. [review]

DeCoursey, T.E.  (1991).  Hydrogen ion currents in rat alveolar epithelial cells.  Biophysical Journal.  60:1243-1253. {First description of voltage-gated proton channels in mammalian cells}

Swift, J. (1729). A modest proposal.

{In view of the world presently being run by neanderthals, Swift's proposal is more relevant than ever!!}

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This page last modified February 12, 2007