TY - JOUR
T1 - Molecular endpoints of Ca2+/calmodulin- and voltage-dependent inactivation of Cav1.3 channels
AU - Tadross, Michael R.
AU - Johny, Manu Ben
AU - Yue, David T.
PY - 2010/3
Y1 - 2010/3
N2 - Ca2+/calmodulin- and voltage-dependent inactivation (GDI and VDI) comprise vital prototypes of Ca2+ channel modulation, rich with biological consequences. Although the events initiating GDI and VDI are known, their downstream mechanisms have eluded consensus. Competing proposals include hinged-lid occlusion of channels, selectivity filter collapse, and allosteric inhibition of the activation gate. Here, novel theory predicts that perturbations of channel activation should alter inactivation in distinctive ways, depending on which hypothesis holds true. Thus, we systematically mutate the activation gate, formed by all S6 segments within Cav1.3. These channels feature robust baseline CDI, and the resulting mutant library exhibits significant diversity of activation, CDI, and VDI. For CDI, a clear and previously unreported pattern emerges: activation-enhancing mutations proportionately weaken inactivation. This outcome substantiates an allosteric CDI mechanism. For VDI, the data implicate a "hinged lidshield" mechanism, similar to a hinged-lid process, with a previously unrecognized feature. Namely, we detect a "shield" in Cav1.3 channels that is specialized to repel lid closure. These findings reveal long-sought downstream mechanisms of inactivation and may furnish a framework for the understanding of Ca2+ channelopathies involving S6 mutations.
AB - Ca2+/calmodulin- and voltage-dependent inactivation (GDI and VDI) comprise vital prototypes of Ca2+ channel modulation, rich with biological consequences. Although the events initiating GDI and VDI are known, their downstream mechanisms have eluded consensus. Competing proposals include hinged-lid occlusion of channels, selectivity filter collapse, and allosteric inhibition of the activation gate. Here, novel theory predicts that perturbations of channel activation should alter inactivation in distinctive ways, depending on which hypothesis holds true. Thus, we systematically mutate the activation gate, formed by all S6 segments within Cav1.3. These channels feature robust baseline CDI, and the resulting mutant library exhibits significant diversity of activation, CDI, and VDI. For CDI, a clear and previously unreported pattern emerges: activation-enhancing mutations proportionately weaken inactivation. This outcome substantiates an allosteric CDI mechanism. For VDI, the data implicate a "hinged lidshield" mechanism, similar to a hinged-lid process, with a previously unrecognized feature. Namely, we detect a "shield" in Cav1.3 channels that is specialized to repel lid closure. These findings reveal long-sought downstream mechanisms of inactivation and may furnish a framework for the understanding of Ca2+ channelopathies involving S6 mutations.
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U2 - 10.1085/jgp.200910308
DO - 10.1085/jgp.200910308
M3 - Article
C2 - 20142517
AN - SCOPUS:77649143136
SN - 0022-1295
VL - 135
SP - 197
EP - 215
JO - Journal of General Physiology
JF - Journal of General Physiology
IS - 3
ER -