An ether -à-go-go K+ current, Ih-eag, contributes to the hyperpolarization of human fusion-competent myoblasts.
1. Two early signs of human myoblast commitment to fusion are membrane potential hyperpolarization and concomitant expression of a non-inactivating delayed rectifier K+ current, IK(NI). This current closely resembles the outward K+ current elicited by rat ether-à-go-go (r-eag) channels in its range of potential for activation and unitary conductance. 2. It is shown that activation kinetics of IK(NI), like those of r-eag, depend on holding potential and on [Mg2+]o, and that IK(NI), like r-eag, is reversibly inhibited by a rise in [Ca2+]i. 3. Forced expression of an isolated human ether-à-go-go K+ channel (h-eag) cDNA in undifferentiated myoblasts generates single-channel and whole-cell currents with remarkable similarity to IK(NI). 4. h-eag current (Ih-eag) is reversibly inhibited by a rise in [Ca2+]i, and the activation kinetics depend on holding potential and [Mg2+]o. 5. Forced expression of h-eag hyperpolarizes undifferentiated myoblasts from -9 to -50 mV, the threshold for the activation of both Ih-eag and IK(NI). Similarly, the higher the density of IK(NI), the more hyperpolarized the resting potential of fusion-competent myoblasts. 6. It is concluded that h-eag constitutes the channel underlying IK(NI) and that it contributes to the hyperpolarization of fusion-competent myoblasts. To our knowledge, this is the first demonstration of a physiological role for a mammalian eag K+ channel.
Bijlenga
P
P
Departement de Physiologie, Centre Medical Universitaire, Division de Recherche Clinique Neuro-Musculaire, Hopital Cantonal Universitaire, CH-1211 Geneva 4, Switzerland.
Occhiodoro
T
T
Liu
J H
JH
Bader
C R
CR
Bernheim
L
L
Fischer-Lougheed
J
J
D000293:Adolescent; D000465:Algorithms; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002459:Cell Fusion / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology*; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D004558:Electric Stimulation; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels; D006801:Humans; D007223:Infant; D008564:Membrane Potentials / Q000502:physiology; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats
D051638:Ether-A-Go-Go Potassium Channels; D015221:Potassium Channels; D002118:Calcium