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Functioning of cx43 hemichannels demonstrated by single channel properties
Jorge E Contreras1, Juan C Sáez, Feliksas F Bukauskas
1Department of Neuroscience, Albert Einstein College of Medicine, NY 10461, USA.
Cell Communication & Adhesion
|December 19, 2003
Summary
This study demonstrates that connexin 43 (Cx43) hemichannels can open, exhibiting specific conductance and voltage gating properties. These findings provide evidence for the functional role of Cx43 hemichannels in cell physiology.
Area of Science:
- Cellular Physiology
- Ion Channel Biophysics
- Gap Junctions
Background:
- Connexin 43 (Cx43) hemichannels are implicated in cell physiology, but their opening has been debated.
- Understanding Cx43 hemichannel function is crucial for various cellular processes.
Purpose of the Study:
- To provide definitive evidence for the opening of connexin 43 (Cx43) hemichannels.
- To characterize the unitary conductance and voltage gating properties of Cx43 hemichannels.
Main Methods:
- Utilized electrophysiological recordings (unitary conductance, voltage gating) in HeLa cells expressing Cx43 and its variants.
- Investigated single hemichannel currents induced by membrane depolarization.
- Compared activity in cells expressing Cx43-EGFP and EGFP-Cx43 chimeras with parental cells.
Main Results:
- Demonstrated Cx43 hemichannel opening at membrane depolarization > +60 mV, with a unitary conductance of ~220 pS.
- Observed slow transitions (>5 ms) between closed and open states, and fast transitions (<1 ms) to a substate (~75 pS).
- Found no functional hemichannel activity in cells expressing EGFP-Cx43, despite surface expression.
Conclusions:
- These data convincingly demonstrate the opening of functional connexin 43 (Cx43) hemichannels.
- Cx43 hemichannels exhibit distinct gating properties similar to cell-cell channels.
- The orientation of Cx43 fusion proteins affects hemichannel functionality.