Journal
BIOPHYSICAL JOURNAL
Volume 81, Issue 1, Pages 137-152Publisher
BIOPHYSICAL SOCIETY
DOI: 10.1016/S0006-3495(01)75687-1
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Funding
- NIGMS NIH HHS [GM54179, R01 GM054179] Funding Source: Medline
- NINDS NIH HHS [NS36706, R01 NS036706] Funding Source: Medline
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We used cell lines expressing wild-type connexin43 (Cx43) and Cx43 fused with enhanced green fluorescent protein (Cx43-EGFP) to examine mechanisms of gap junction channel gating. Previously it was suggested that each hemichannel in a cell-cell channel possesses two gates, a fast gate that closes channels to a nonzero conductance or residual state via fast (< similar to2 ms) transitions and a slow gate that fully closes channels via slow transitions (> similar to 10 ms). Here we demonstrate that transjunctional voltage (V-j) regulates both gates and that they are operating in series and in a contingent manner in which the state of one gate affects gating of the other. Cx43-EGFP channels lack fast V-j gating to a residual state but show slow V-j gating. Both Cx43 and Cx43-EGFP channels exhibit slow gating by chemical uncouplers such as CO2 and alkanols. Chemical uncouplers do not induce obvious changes in Cx43-EGFP junctional plaques, indicating that uncoupling is not caused by dispersion or internalization of junctional plaques. Similarity of gating transitions during chemical gating and slow V-j gating suggests that both gating mechanisms share common structural elements. Cx43/Cx43-EGFP heterotypic channels showed asymmetrical V-j gating with fast transitions between open and residual states only when the Cx43 side was relatively negative. This result indicates that the fast V-j gate of Cx43 hemichannels closes for relative negativity at its cytoplasmic end.
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