Short-term regulation of excitation-contraction coupling by the beta1a subunit in adult mouse skeletal muscle.
The beta1a subunit of the skeletal muscle voltage-gated Ca2+ channel plays a fundamental role in the targeting of the channel to the tubular system as well as in channel function. To determine whether this cytosolic auxiliary subunit is also a regulatory protein of Ca2+ release from the sarcoplasmic reticulum in vivo, we pressure-injected the beta1a subunit into intact adult mouse muscle fibers and recorded, with Fluo-3 AM, the intracellular Ca2+ signal induced by the action potential. We found that the beta1a subunit significantly increased, within minutes, the amplitude of Ca2+ release without major changes in its time course. beta1a subunits with the carboxy-terminus region deleted did not show an effect on Ca2+ release. The possibility that potentiation of Ca2+ release is due to a direct interaction between the beta1a subunit and the ryanodine receptor was ruled out by bilayer experiments of RyR1 single-channel currents and also by Ca2+ flux experiments. Our data suggest that the beta1a subunit is capable of regulating E-C coupling in the short term and that the integrity of the carboxy-terminus region is essential for its modulatory effect.
García
María C
MC
Departmento de Farmacología, Centro de Investigación y de Estudios Avanzados del I.P.N., Mexico, D.F. 07360, Mexico.
Carrillo
Elba
E
Galindo
José M
JM
Hernández
Ascensión
A
Copello
Julio A
JA
Fill
Michael
M
Sánchez
Jorge A
JA
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D051379:Mice; D008807:Mice, Inbred BALB C; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D021122:Protein Subunits / Q000378:metabolism*
C492923:Cacnb1 protein, mouse; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D021122:Protein Subunits