TY - JOUR
T1 - Mechanism of Ca2+-sensitive inactivation of L-type Ca2+ channels
AU - Imredy, John P.
AU - Yue, David T.
N1 - Funding Information:
We thank T. C. Hwang for advice on handling of orthovanadate and M. S. de Leon and B. A. Lewis for helpful comments and discussion. This work was supported by the National Institutes of Health (5 T32 CM07057 to J. P. I. and R29 HL43307 to D. T. Y.) and by an Established Investigatorship (D. T. Y.) from the American Heart Association.
PY - 1994/6
Y1 - 1994/6
N2 - Many high threshold, voltage-gated Ca2+ channels, including the dihydropyridine-sensitive class (L-type), inactivate in response not only to voltage, but also to entry of Ca2+. Despite the physiological importance of this Ca2+-sensitive inactivation, its molecular mechanism is understood only in broad outline. We now demonstrate that Ca2+-dependent inactivation transpires by a Ca2+-induced shift of channel gating to a low open probability mode, distinguished by a more than 100-fold reduction of entry rate to the open state. A gating mechanism that explains this shift quantitatively and enables successful separation of Ca2+- and voltage-sensitive forms of inactivation is deduced and tested. Finally, both calmodulin activation and channel (de)phosphorylation are excluded as significant signaling events underlying Ca 2+-induced mode shifts, leaving direct binding of Ca2+ to the channel as a likely chemical initiation event for inactivation.
AB - Many high threshold, voltage-gated Ca2+ channels, including the dihydropyridine-sensitive class (L-type), inactivate in response not only to voltage, but also to entry of Ca2+. Despite the physiological importance of this Ca2+-sensitive inactivation, its molecular mechanism is understood only in broad outline. We now demonstrate that Ca2+-dependent inactivation transpires by a Ca2+-induced shift of channel gating to a low open probability mode, distinguished by a more than 100-fold reduction of entry rate to the open state. A gating mechanism that explains this shift quantitatively and enables successful separation of Ca2+- and voltage-sensitive forms of inactivation is deduced and tested. Finally, both calmodulin activation and channel (de)phosphorylation are excluded as significant signaling events underlying Ca 2+-induced mode shifts, leaving direct binding of Ca2+ to the channel as a likely chemical initiation event for inactivation.
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U2 - 10.1016/0896-6273(94)90446-4
DO - 10.1016/0896-6273(94)90446-4
M3 - Article
C2 - 8011340
AN - SCOPUS:0028179582
SN - 0896-6273
VL - 12
SP - 1301
EP - 1318
JO - Neuron
JF - Neuron
IS - 6
ER -