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Transfer of L-type Calcium Channel IVS6 Segment Increases Phenylalkylamine Sensitivity of (*)

F. Döring,V. E. Degtiar,M. Grabner,J. Striessnig,S. Hering,H. Glossmann

Published 1996 in Journal of Biological Chemistry

ABSTRACT

Conditioned (“use-dependent”) inhibition by phenylalkylamines (PAAs) is a characteristic property of L-type calcium (Ca) channels. To determine the structural elements of the PAA binding domain we transferred sequence stretches of the pore-forming regions of repeat III and/or IV from the skeletal muscle α subunit (α) to the class A α subunit (α) and expressed these chimeras together with β and α/ subunits in Xenopus oocytes. The corresponding barium currents (I) were tested for PAA sensitivity during trains of depolarizing test pulses (conditioned block). I of oocytes expressing the α subunit were only weakly inhibited by PAAs (less than 10% conditioned block of I during a 100-ms pulse train of 0.1 Hz). Transfer of the transmembrane segment IVS6 from α to α produced an enhancement of PAA sensitivity of the resulting α/α chimera comparable to L-type α subunits (about 35% conditioned block of I during a 100-ms pulse train of 0.1 Hz). Our results demonstrate that substitution of 11 amino acids within the segment IVS6 of α with the corresponding residues of α is sufficient to transfer L-type PAA sensitivity into the low sensitive class A Ca channel.

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