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Opposing modulation of Cx26 gap junctions and hemichannels by CO2

Nijjar, Sarbjit; Maddison, Daniel; Meigh, Louise; Wolf, Elizabeth; Rodgers, Thomas; Cann, Martin; Dale, Nicholas

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Sarbjit Nijjar

Daniel Maddison

Louise Meigh

Elizabeth Wolf

Thomas Rodgers

Nicholas Dale


Cx26 hemichannels open in response to moderate elevations of CO2 (PCO2 55 mmHg) via a carbamylation reaction that depends on residues K125 and R104. Here we investigate the action of CO2 on Cx26 gap junctions. Using a dye transfer assay, we found that an elevated PCO2 of 55 mmHg greatly delayed the permeation of a fluorescent glucose analogue (NBDG) between HeLa cells coupled by Cx26 gap junctions. However, the mutations K125R or R104A abolished this effect of CO2. Whole cell recordings demonstrated that elevated CO2 reduced the Cx26 gap junction conductance (median reduction 66.7%, 95% confidence interval, 50.5 to 100.0%) but had no effect on Cx26K125R or Cx31 gap junctions. CO2 can cause intracellular acidification. Using 30 mM propionate, we found that acidification in the absence of a change in PCO2 caused a median reduction in the gap junction conductance of 41.7% (26.6 to 53.7%). This effect of propionate was unaffected by the K125R mutation (median reduction 48.1%, 28.0 to 86.3%). pH‐dependent and CO2‐dependent closure of the gap junction are thus mechanistically independent. Mutations of Cx26 associated with the Keratitis Ichthyosis Deafness syndrome (N14K, A40V and A88V), in combination with the mutation M151L, also abolished the CO2‐dependent gap junction closure. Elastic network modelling suggests that the lowest entropy state when CO2 is bound, is the closed configuration for the gap junction but the open state for the hemichannel. The opposing actions of CO2 on Cx26 gap junctions and hemichannels thus depend on the same residues and presumed carbamylation reaction.


Nijjar, S., Maddison, D., Meigh, L., Wolf, E., Rodgers, T., Cann, M., & Dale, N. (2021). Opposing modulation of Cx26 gap junctions and hemichannels by CO2. The Journal of Physiology, 599(1), 103-118.

Journal Article Type Article
Acceptance Date Oct 2, 2020
Online Publication Date Oct 6, 2020
Publication Date Jan 1, 2021
Deposit Date Oct 14, 2020
Publicly Available Date Nov 4, 2020
Journal Journal of Physiology
Print ISSN 0022-3751
Electronic ISSN 1469-7793
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 599
Issue 1
Pages 103-118
Public URL


Published Journal Article (Advance online version) (4.6 Mb)

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Copyright Statement
Advance online version © 2020 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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