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Related Concept Videos

Gap Junctions01:37

Gap Junctions

Multicellular organisms employ a variety of ways for cells to communicate with each other. Gap junctions are specialized proteins that form pores between neighboring cells in animals, connecting the cytoplasm between the two, and allowing for the exchange of molecules and ions. They are found in a wide range of invertebrate and vertebrate species, mediate numerous functions including cell differentiation and development, and are associated with numerous human diseases, including cardiac and...
Gap Junctions01:27

Gap Junctions

The cytoplasm of adjacent animal cells can exchange small molecules, ions, and secondary messengers via the communication channels which form the gap junctions. These junctions comprise a few hundred to thousands of molecular channels, each made of two halves, called the connexon hemichannel. A connexon is a hexamer of six transmembrane connexin proteins, which assemble radially, thus forming a pore or channel in the center. One connexon hemichannel docks with a corresponding connexon on the...
Non-gated Ion Channels01:24

Non-gated Ion Channels

Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
Non-gated Ion Channels01:24

Non-gated Ion Channels

Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
Contact-dependent Signaling01:19

Contact-dependent Signaling

Contact-dependent signaling, as the name suggests, requires that communicating cells be in direct contact with each other. This is achieved either through receptor-ligand interactions or by specialized cytoplasmic channels that allow the flow of small molecules between cells. In animal cells, channels called gap junctions facilitate contact-dependent signaling in certain tissues, whereas, plasmodesmata perform a similar function in plants.
Gap Junctions
In animal cells, gap junctions are formed...
Ligand-gated Ion Channels01:19

Ligand-gated Ion Channels

Ligand-gated ion channels are transmembrane proteins with a channel for ions to pass through and a binding site for a ligand. The channel opens only when a ligand attaches to the binding site.
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that include the...

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Lens Connexin Channels Show Differential Permeability to Signaling Molecules.

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Connexin43 and connexin50 channels exhibit different permeability to the second messenger inositol triphosphate.

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A study of the outward background current conductance g<sub>K1</sub>, the pacemaker current conductance g<sub>f</sub>, and the gap junction conductance g<sub>j</sub> as determinants of biological pacing in single cells and in a two-cell syncytium using the dynamic clamp.

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Related Experiment Video

Updated: May 10, 2026

Mechanical Stimulation-induced Calcium Wave Propagation in Cell Monolayers: The Example of Bovine Corneal Endothelial Cells
10:46

Mechanical Stimulation-induced Calcium Wave Propagation in Cell Monolayers: The Example of Bovine Corneal Endothelial Cells

Published on: July 16, 2013

Cyclic nucleotide permeability through unopposed connexin hemichannels.

Virginijus Valiunas1

  • 1Department of Physiology and Biophysics, Stony Brook University Stony Brook, NY, USA.

Frontiers in Pharmacology
|June 14, 2013
PubMed
Summary

Gap junction hemichannels, formed by connexins, allow cyclic adenosine monophosphate (cAMP) to enter cells. This suggests hemichannels are a pathway for cAMP signaling between cells.

Keywords:
connexin26connexin43cyclic AMPelectrophysiologygap junctionpermeability

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Related Experiment Videos

Last Updated: May 10, 2026

Mechanical Stimulation-induced Calcium Wave Propagation in Cell Monolayers: The Example of Bovine Corneal Endothelial Cells
10:46

Mechanical Stimulation-induced Calcium Wave Propagation in Cell Monolayers: The Example of Bovine Corneal Endothelial Cells

Published on: July 16, 2013

Recording Gap Junction Current from Xenopus Oocytes
09:04

Recording Gap Junction Current from Xenopus Oocytes

Published on: January 21, 2022

Assessment of Open Probability of the Mitochondrial Permeability Transition Pore in the Setting of Coenzyme Q Excess
07:35

Assessment of Open Probability of the Mitochondrial Permeability Transition Pore in the Setting of Coenzyme Q Excess

Published on: June 1, 2022

Area of Science:

  • Cell biology
  • Molecular signaling
  • Biophysics

Background:

  • Cyclic adenosine monophosphate (cAMP) acts as a crucial intracellular and intercellular second messenger.
  • Understanding the membrane permeability of cAMP is vital for its potential role in autocrine and paracrine signaling.
  • Gap junction hemichannels, constructed from connexins, are investigated as a potential entry route for cyclic nucleotides into cells.

Purpose of the Study:

  • To determine if gap junction hemichannels serve as an entry pathway for cyclic nucleotides into cells.
  • To investigate the permeability of connexin43 (Cx43) and connexin26 (Cx26) hemichannels to cAMP.
  • To explore the role of hemichannel activity in cAMP uptake and signaling.

Main Methods:

  • HeLa cells stably expressing Cx43 and Cx26 were utilized.
  • Cells were transfected with the sea urchin sperm (SpIH) channel as a cAMP sensor.
  • Whole-cell/perforated patch clamp electrophysiology was employed to record SpIH-derived currents (I m).
  • Experiments involved perfusing cells with cAMP-containing solutions under varying extracellular Ca(2+) concentrations and depolarization conditions.
  • The effect of the gap junction blocker carbenoxolone was assessed.

Main Results:

  • Perfusion with cAMP in Ca(2+)-free solution increased I m five to sevenfold, correlating with hemichannel activity.
  • Cell depolarization in Ca(2+)-free conditions with cAMP also elevated I m.
  • High extracellular Ca(2+) (mM levels) inhibited hemichannel activity and cAMP-induced current increases.
  • Carbenoxolone blocked cAMP uptake, indicating hemichannel involvement.
  • Lowered extracellular Ca(2+) and cell depolarization enhanced hemichannel open probability.

Conclusions:

  • Cx43 and Cx26 hemichannels are permeable to cAMP.
  • Hemichannels represent a potential pathway for extracellular cAMP uptake into cells.
  • This uptake mechanism suggests a role for hemichannels in cAMP-mediated cell-to-cell communication.