Molecular pharmacology
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Molecular pharmacology · Sep 2008
Alternative splicing of the Ca2+ channel beta4 subunit confers specificity for gabapentin inhibition of Cav2.1 trafficking.
Gabapentin is well established as an effective treatment for neuropathic pain; however, little is known about its mechanism of action. It binds with high affinity to Ca2+ channel alpha2delta subunits that are expressed in dorsal root ganglia. Mutation of a single alpha2delta amino acid, R217A, eliminates both gabapentin binding and analgesic efficacy. ⋯ Our principal findings are as follows: 1) gabapentin inhibits trafficking of recombinant Ca(v)2.1 Ca2+ channels in X. laevis oocytes; 2) gabapentin inhibition occurs in the presence of the Ca2+ channel beta4a subunit but not in the presence of beta4b; 3) gabapentin does not affect Ca(v)2.1 voltage-dependent gating parameters; 4) inhibition of Ca(v)2.1 trafficking is highly dependent on beta-subunit concentration; and 5) gabapentin inhibition of Ca(v)2.1 trafficking can be reversed by the alpha2delta R217A mutation. Overall, our results suggest that gabapentin reduces the number of beta4a-bound Ca(v)2.1 complexes that are successfully trafficked to the plasma membrane. This mechanism may help to explain why gabapentin is both effective and selective in the treatment of neuropathic pain states that involve up-regulation of alpha2delta subunits.