Inactivation of expressed and conducting rCx46 hemichannels by phosphorylation.
Hemichannels of rat connexin 46 (rCx46) were expressed in Xenopus laevis oocytes and analysed by two-electrode voltage-clamp experiments. It is established that rCx46 hemichannels can be activated at low external Ca2+ and positive membrane potentials. Upon larger depolarizations, the hemichannels of oocytes activate in a time-dependent manner, occasionally followed by a spontaneous inactivation. We found that, in the absence of inactivation, treatment of oocytes with 1-oleoyl-2-acetyl-sn-glycerol (OAG), an activator of protein kinase C (PKC), reversibly reduced the amplitude of the rCx46-mediated current and, after an incubation time of about 30 min, induced inactivation of the voltage-dependent current. After wash-out of OAG the corresponding membrane conductance increased and the inactivation behaviour disappeared. The OAG-induced inactivation, as well as the spontaneous inactivation, could be removed by application of the specific PKC inhibitor calphostin C and also by phloretin. The data provide evidence that the activation and inhibition of PKC affect the rCx46-mediated membrane conductance as well as the voltage-dependent current inactivation in an inverse manner.
Ngezahayo
A
A
Institut für Biophysik, Universität Hannover, Herrenhäuser Strasse 2, D-30419 Hannover, Germany.
Zeilinger
C
C
Todt
I
I
Marten
I
I
Kolb
H A
HA
D000818:Animals; D017630:Connexins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D014982:Xenopus laevis
D017630:Connexins; D004075:Diglycerides; C487370:Gja3 protein, rat; C038237:1-oleoyl-2-acetylglycerol; D011493:Protein Kinase C