한빛사논문
- 조회610
Seong-Ki Lee1, Rossana Occhipinti1, Fraser J. Moss1, Mark D. Parker1,2, Irina I. Grichtchenko3 and Walter F. Boron1,4,5
1Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
2Department of Physiology and Biophysics, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York
3Department of Biology, Metropolitan State University of Denver, Denver, Colorado
4Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio
5Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio
Correspondence: Prof. Walter F. Boron
Abstract
Background: Differentiating among HCO3−, CO3=, and H+ movements across membranes has long seemed impossible. We now seek to discriminate unambiguously among three alternate mechanisms: the inward flux of 2 HCO3− (mechanism 1), the inward flux of 1 CO3= (mechanism 2), and the CO2/HCO3−-stimulated outward flux of 2 H+ (mechanism 3).
Methods: As a test case, we use electrophysiology and heterologous expression in Xenopus oocytes to examine SLC4 family members that appear to transport “bicarbonate” (“HCO3−”).
Results: First, we note that cell-surface carbonic anhydrase should catalyze the forward reaction CO2+OH–→HCO3− if HCO3− is the substrate; if it is not, the reverse reaction should occur. Monitoring changes in cell-surface pH (ΔpHS) with or without cell-surface carbonic anhydrase, we find that the presumed Cl-“HCO3” exchanger AE1 (SLC4A1) does indeed transport HCO3− (mechanism 1) as long supposed, whereas the electrogenic Na/“HCO3” cotransporter NBCe1 (SLC4A4) and the electroneutral Na+-driven Cl-“HCO3” exchanger NDCBE (SLC4A8) do not. Second, we use mathematical simulations to show that each of the three mechanisms generates unique quantities of H+ at the cell surface (measured as ΔpHS) per charge transported (measured as change in membrane current, ΔIm). Calibrating ΔpHS/ΔIm in oocytes expressing the H+ channel HV1, we find that our NBCe1 data align closely with predictions of CO3= transport (mechanism 2), while ruling out HCO3− (mechanism 1) and CO2/HCO3−-stimulated H+ transport (mechanism 3).
Conclusions: Our surface chemistry approach makes it possible for the first time to distinguish among HCO3−, CO3=, and H+ fluxes, thereby providing insight into molecular actions of clinically relevant acid-base transporters and carbonic-anhydrase inhibitors.
논문정보
- Research article
- 2022년 10월 (BRIC 등록일 2022-11-04)
- 국외 연구진
- 생명과학 > 생리학
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