Regulation of connexons composed of human connexin26 (hCx26) by temperature

This report shows that temperature is a latent regulator of the voltage-dependent conductance of hemichannels composed of hCx26. The latter were expressed in Xenopus oocytes by injection of a mixture of hCx26 cRNA and antisense of endogenous Cx38 (anti-Cx38). At 24-25 degrees C, voltage clamp of oocytes at potentials above -40 mV evoked outward currents which were not observed in control oocytes. These currents were reversibly affected by change in temperature. Increasing temperature of the bath solution amplified gradually, whereas decreasing bath temperatures below 20 degrees C reduced the current. Furthermore analysis revealed that temperature-dependent increase of the conductance of the hemichannels did not correlate with a change of the apparent gating charge, whereas the half-activation voltage V(1/2) of the hemichannel was affected by a temperature change. It is proposed that this finding correlates with a temperature-dependent transition into an open state above 20 degrees C. In addition, a temperature-dependent release of Lucifer Yellow from loaded liposomes containing reconstituted purified and hCx26 hemichannels was observed, which indicate that a temperature-dependent regulation of the permeability of hCx26 hemichannels is not related to intracellular mediators. The involvement of temperature to modulate hemichannels as well as of the corresponding gap junction channel composed of hCx26 at physiological condition is discussed.