Ns. Gee et al., THE NOVEL ANTICONVULSANT DRUG, GABAPENTIN (NEURONTIN), BINDS TO THE ALPHA(2)DELTA SUBUNIT OF A CALCIUM-CHANNEL, The Journal of biological chemistry, 271(10), 1996, pp. 5768-5776
Gabapentin (1-(aminomethyl)cyclohexane acetic acid; Neurontin) is a no
vel anticonvulsant drug, with a mechanism of action apparently dissimi
lar to that of other antiepileptic agents. We report here the isolatio
n and characterization of a [H-3]gabapentin binding protein from pig c
erebral cortex membranes. The detergent-solubilized binding protein wa
s purified 1022-fold, in a six-step column-chromatographic procedure,
with a yield of 3.9%. The purified protein had an apparent subunit M(r
) of 130,000, and was heavily glycosylated. The partial N-terminal ami
no acid sequence of the M(r) 130,000 polypeptide, EPFPSAVTIK, was iden
tical to that reported for the alpha(2) delta subunit of the L-type Ca
2+ channel from rabbit skeletal muscle (Hamilton, S. L., Hawkes, M. J.
, Brush, K., Cook, R., Chang, R. J., and Smilowitz, H. M. (1989) Bioch
emistry 28, 7820-7828). High levels of [H-3]gabapentin binding sites w
ere found in membranes prepared from rat brain, heart and skeletal mus
cle. Binding of [H-3]gabapentin to COS-7 cells transfected with alpha(
2) delta cDNA was elevated >10-fold over controls, consistent with the
expression of alpha(2) delta protein, as measured by Western blotting
. Finally, purified L-type Ca2+ channel complexes were fractionated, u
nder dissociating conditions, on an ion-exchange column; [H-3]gabapent
in binding activity closely followed the elution of the alpha(2) delta
subunit. [H-3]Gabapentin is the first pharmacological agent described
that interacts with an alpha(2) delta subunit of a voltage-dependent
Ca2+ channel.