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Opening hemichannels in nonjunctional membrane stimulates gap junction formation.
1Department of Physiology and Biophysics, University of California at Irvine, Irvine, California, USA.
Biophysical Journal
|January 30, 2004
Summary
Functional hemichannel activity, when reaching a threshold current, rapidly increases gap junction formation in Xenopus oocytes. This process is influenced by connexin types and external calcium levels.
Area of Science:
- Cell Biology
- Membrane Biophysics
- Ion Channel Physiology
Background:
- Gap junctions mediate direct cell-to-cell communication.
- Connexins form hemichannels and gap junctions, but their relationship in formation is unclear.
Purpose of the Study:
- To investigate the role of hemichannel activity in stimulating gap junction formation.
- To determine factors influencing the rate and extent of stimulated gap junction formation.
Main Methods:
- Studied Xenopus laevis oocytes expressing specific connexins.
- Measured junctional conductance (G(j)) and whole-cell hemichannel conductances (G(hemi)).
- Manipulated hemichannel activity, external calcium, and membrane glycoproteins.
Main Results:
- No initial correlation between G(j) and G(hemi), but threshold hemichannel current rapidly increased G(j).
- Hemichannel activity stimulated G(j) even between non-interacting connexin types.
- Stimulated G(j) growth rate depended on hemichannel conductances and external calcium; formation was faster in low calcium and after lectin treatment.
Conclusions:
- Hemichannel activity can trigger or enhance gap junction formation, potentially by reducing extracellular space.
- External calcium modulates the kinetics but not the final level of stimulated gap junction formation.
- These findings suggest a novel mechanism for regulating cell-cell communication in vivo.