Gating and regulation of connexin 43 (Cx43) hemichannels
AUTOR(ES)
Contreras, Jorge E.
FONTE
National Academy of Sciences
RESUMO
Connexin 43 (Cx43) nonjunctional or “unapposed” hemichannels can open under physiological or pathological conditions. We characterize hemichannels comprised of Cx43 or Cx43-EGFP (Cx43 with enhanced GFP fused to the C terminus) expressed in HeLa cells. Channel opening was induced at potentials greater than +60 mV. Open probability appeared to be very low. No comparable opening was detected in the parental, nontransfected HeLa cells. Conductance of fully open single hemichannels was ≈220 pS, which is approximately double that of Cx43 cell–cell channels. Cx43 hemichannels exhibited two types of gating: fast transitions (<1 ms) between the fully open state and a substate of ≈75 pS and slow transitions (>5 ms) between either open state and the fully closed state. Cx43-EGFP hemichannels exhibited only slow transitions (>5 ms) between closed and fully open states. These properties resemble those of the corresponding Cx43 and Cx43-EGFP cell–cell channels. Cx43 with EGFP on the N terminus (EGFP-Cx43) inserted into the surface and formed plaques but did not form hemichannels or cell–cell channels. Hemichannel blockers, 18β-glycyrrhetinic acid or La3+, blocked depolarization-induced currents. Uptake of ethidium bromide (i) was faster in Cx43 and Cx43-EGFP than parental and EGFP-Cx43 cells, (ii) was directly correlated with Cx43-EGFP expression, (iii) was reduced by hemichannel blockers, and (iv) occurred at the same low rate in EGFP-Cx43 and parental cells. Although hemichannel opening was not detected electrophysiologically at the resting potential, infrequent or brief opening could account for ethidium bromide uptake. Opening of Cx43 hemichannels may mediate normal signaling or be deleterious.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=208767Documentos Relacionados
- PH regulation of connexin43: molecular analysis of the gating particle.
- Molecular basis of calcium regulation in connexin-32 hemichannels
- Coupling asymmetry of heterotypic connexin 45/ connexin 43-EGFP gap junctions: Properties of fast and slow gating mechanisms
- Incompatibility of connexin 40 and 43 Hemichannels in gap junctions between mammalian cells is determined by intracellular domains.
- Regulation of gap junctional charge selectivity in cells coexpressing connexin 40 and connexin 43