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Mol Pharmacol. 2018 Jul 6. pii: mol.118.112441. doi: 10.1124/mol.118.112441. [Epub ahead of print]

Molecular determinants of the differential modulation of Cav1.2 and Cav1.3 by nifedipine and FPL 64176.

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Purdue University.
Purdue University


Nifedipine and FPL 64176 (FPL), which block and potentiate L-type voltage-gated Ca2+ channels respectively, more potently modulate Cav1.2 than Cav1.3. To identify potential strategies for developing subtype-selective inhibitors, we investigated the role of divergent amino acid residues in transmembrane domains IIIS5 and the extracellular IIIS5-3P loop region in modulation of these channels by nifedipine and FPL. Insertion of the extracellular IIIS5-3P loop from Cav1.2 into Cav1.3 (Cav1.3+) reduced the IC50 of nifedipine from 289 nM to 101 nM, and substitution of S1100 with an A residue, as in Cav1.2, accounted for this difference. Substituting M1030 in IIIS5 to V in Cav1.3+ (Cav1.3+V) further reduced the IC50 of nifedipine to 42 nM. FPL increased current amplitude with an EC50 of 854 nM in Cav1.3, 103 nM in Cav1.2, and 99 nM in Cav1.3+V. In contrast to nifedipine block, substitution of M1030 to V in Cav1.3 had no effect on potency of FPL potentiation of current amplitude, but significantly slowed deactivation in the presence and absence of 10 μM FPL. FPL had no effect on deactivation of Cav1.3/DHPi, a channel with very low sensitivity to nifedipine block (IC50 ~ 93 μM), but did shift the voltage-dependence of activation by ~-10 mV. We conclude that the M/V variation in IIIS5 and the S/A variation in the IIIS5-3P loop of Cav1.2 and Cav1.3 largely determine the difference in nifedipine potency between these two channels, but the difference in FPL potency is determined solely by divergent amino acids in the IIIS5-3P loop.


Calcium channel blockers; Ion channels

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