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09:04
Recording Gap Junction Current from Xenopus Oocytes
Published on: January 21, 2022
Gap junction channels exhibit connexin-specific permeability to cyclic nucleotides
Giedrius Kanaporis1, Gulistan Mese, Laima Valiuniene
1Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA.
The Journal of General Physiology
|April 2, 2008
Summary
Connexin 43 (Cx43) gap junctions efficiently transfer cyclic adenosine monophosphate (cAMP), a crucial second messenger. Cx43 channels facilitate rapid cAMP cell-to-cell communication, unlike Cx40 and Cx26 channels which show lower permeability.
Area of Science:
- Cell Biology
- Biophysics
- Molecular Biology
Background:
- Gap junction channels, formed by connexins, mediate direct cell-to-cell communication.
- These channels exhibit connexin-dependent biophysical properties, influencing the passage of various molecules, including second messengers.
- Understanding the permeability of gap junctions to specific second messengers like cyclic adenosine monophosphate (cAMP) is vital for comprehending intercellular signaling.
Purpose of the Study:
- To determine the permeability of gap junction channels formed by connexin 43 (Cx43), connexin 40 (Cx40), and connexin 26 (Cx26) to cyclic adenosine monophosphate (cAMP).
- To compare the cAMP permeability of homotypic channels composed of Cx43, Cx40, and Cx26.
- To elucidate the functional implications of differential cAMP permeability for intercellular communication and cellular responses.
Main Methods:
- Simultaneous measurements of junctional conductance and intercellular transfer of cAMP.
- Utilizing a reporter gene (SpIH) in recipient cells for cAMP detection.
- Introducing cAMP via patch pipette into one cell of a coupled pair and recording SpIH-derived currents in the other.
Main Results:
- Cyclic adenosine monophosphate (cAMP) transfer through gap junction channels was quantified by a significant increase in SpIH-derived currents.
- Homotypic Cx43 channels demonstrated substantial cAMP permeability across a range of conductances.
- Homotypic Cx40 and Cx26 channels exhibited significantly reduced cAMP permeability compared to Cx43 channels, with cAMP/K+ permeability ratios of 0.18 (Cx43), 0.027 (Cx26), and 0.018 (Cx40).
Conclusions:
- Connexin 43 (Cx43) channels are considerably more permeable to cAMP than Cx26 and Cx40 channels, indicating distinct selectivity for negatively charged solutes.
- Cx43-mediated rapid cAMP delivery is sufficient to trigger intracellular responses before degradation.
- Reduced cAMP permeability of Cx26 and Cx40 channels may limit their ability to induce functional changes in recipient cells via cAMP signaling.
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