Functional and molecular identification of ERG channels in murine portal vein myocytes.
Ion channels encoded by ether-à-go-go-related genes (ERG) have been implicated in repolarization of the cardiac action potential and also as components of the resting membrane conductance in various cells. The aim of the present study was to determine whether ERG channels were expressed in smooth muscle cells isolated from portal vein. RT-PCR demonstrated the expression of murine ERG (mERG), and real-time quantitative PCR showed that the mERG1b isoform predominated over the mERG1a, mERG2, and mERG3 in portal vein. Single myocytes from portal vein displayed membrane staining with an ERG1-specific antibody. Whole cell voltage-clamp experiments were performed to determine whether portal vein myocytes expressed functional ERG channels. Large inward currents with distinctive kinetics were elicited that were inhibited rapidly by E-4031 (mean amplitude of the E-4031-sensitive current at -120 mV was -205 +/- 24 pA; n = 14). Deactivation of the E-4031-sensitive current was voltage dependent (mean time constants at -80 and -120 mV were 103 +/- 9 and 33 +/- 2 ms, respectively; n = 13). Because of the rapid kinetics of mERG currents at more negative potentials, there was a substantial noninactivating "window" current that reached a maximum of -66 +/- 10 pA at -70 mV. Complete portal veins exhibited spontaneous contractile activity in isometric tension experiments, and this activity was modified significantly by E-4031. These data show that ERG channels are expressed in murine portal vein myocytes that may contribute to the resting membrane conductance.
Ohya
Susumu
S
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno 89557-0046, USA.
Horowitz
Burton
B
Greenwood
Iain A
IA
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D027682:Cation Transport Proteins; D002469:Cell Separation; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D026901:Membrane Transport Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011169:Portal Vein / Q000166:cytology / Q000378:metabolism*; D015221:Potassium Channels / Q000096:biosynthesis* / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014661:Vasoconstriction / Q000502:physiology
D027682:Cation Transport Proteins; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; C486376:KCNH7 protein, human; C498827:Kcne3 protein, mouse; C000606915:Kcnh2 protein, mouse; D026901:Membrane Transport Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D020033:Protein Isoforms