Caffeine-induced release of intracellular Ca2+ from Chinese hamster ovary cells expressing skeletal muscle ryanodine receptor. Effects on full-length and carboxyl-terminal portion of Ca2+ release channels.
The ryanodine receptor (RyR)/Ca2+ release channel is an essential component of excitation-contraction coupling in striated muscle cells. To study the function and regulation of the Ca2+ release channel, we tested the effect of caffeine on the full-length and carboxyl-terminal portion of skeletal muscle RyR expressed in a Chinese hamster ovary (CHO) cell line. Caffeine induced openings of the full length RyR channels in a concentration-dependent manner, but it had no effect on the carboxyl-terminal RyR channels. CHO cells expressing the carboxyl-terminal RyR proteins displayed spontaneous changes of intracellular [Ca2+]. Unlike the native RyR channels in muscle cells, which display localized Ca2+ release events (i.e., "Ca2+ sparks" in cardiac muscle and "local release events" in skeletal muscle), CHO cells expressing the full length RyR proteins did not exhibit detectable spontaneous or caffeine-induced local Ca2+ release events. Our data suggest that the binding site for caffeine is likely to reside within the amino-terminal portion of RyR, and the localized Ca2+ release events observed in muscle cells may involve gating of a group of Ca2+ release channels and/or interaction of RyR with muscle-specific proteins.
Bhat
M B
MB
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Zhao
J
J
Zang
W
W
Balke
C W
CW
Takeshima
H
H
Wier
W G
WG
Ma
J
J
D000818:Animals; D016466:CHO Cells / Q000737:chemistry / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D016257:Fura-2; D049452:Green Fluorescent Proteins; D006352:Heart Ventricles / Q000166:cytology; D007091:Image Processing, Computer-Assisted; D007425:Intracellular Membranes / Q000737:chemistry; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008164:Luminescent Proteins; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000502:physiology; D017434:Protein Structure, Tertiary; D011817:Rabbits; D051381:Rats; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D000697:Central Nervous System Stimulants; D008164:Luminescent Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D049452:Green Fluorescent Proteins; D002110:Caffeine; D002118:Calcium; D016257:Fura-2