T-type alpha 1H Ca2+ channels are involved in Ca2+ signaling during terminal differentiation (fusion) of human myoblasts.
Mechanisms underlying Ca(2+) signaling during human myoblast terminal differentiation were studied using cell cultures. We found that T-type Ca(2+) channels (T-channels) are expressed in myoblasts just before fusion. Their inhibition by amiloride or Ni(2+) suppresses fusion and prevents an intracellular Ca(2+) concentration increase normally observed at the onset of fusion. The use of antisense oligonucleotides indicates that the functional T-channels are formed by alpha1H subunits. At hyperpolarized potentials, these channels allow a window current sufficient to increase [Ca(2+)](i). As hyperpolarization is a prerequisite to myoblast fusion, we conclude that the Ca(2+) signal required for fusion is produced when the resting potential enters the T-channel window. A similar mechanism could operate in other cell types of which differentiation implicates membrane hyperpolarization.
Bijlenga
P
P
Département de Physiologie, Centre Médical Universitaire, and Division de Recherche Clinique Neuro-Musculaire, Hôpital Cantonal Universitaire, CH-1211 Geneva 4, Switzerland.
Liu
J H
JH
Espinos
E
E
Haenggeli
C A
CA
Fischer-Lougheed
J
J
Bader
C R
CR
Bernheim
L
L
D002118:Calcium / Q000378:metabolism*; D020747:Calcium Channels, T-Type / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D006801:Humans; D017136:Ion Transport; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction
D020747:Calcium Channels, T-Type; D002118:Calcium