Inhibition of recombinant N-type and native high voltage-gated neuronal Ca2+ channels by AdGABA: mechanism of action studies.
High-voltage activated Ca(2+) (Ca(V)) channels play a key role in the regulation of numerous physiological events by causing transient changes in the intracellular Ca(2+) concentration. These channels consist of a pore-forming Ca(V)α(1) protein and three auxiliary subunits (Ca(V)β, Ca(V)α(2)δ and Ca(V)γ). Ca(V)α(2)δ is an important component of Ca(V) channels in many tissues and of great interest as a drug target. It is well known that anticonvulsant agent gabapentin (GBP) binds to Ca(V)α(2)δ and reduces Ca(2+) currents by modulating the expression and/or function of the Ca(V)α(1) subunit. Recently, we showed that an adamantane derivative of GABA, AdGABA, has also inhibitory effects on Ca(V) channels. However, the importance of the interaction of AdGABA with the Ca(V)α(2)δ subunit has not been conclusively demonstrated and the mechanism of action of the drug has yet to be elucidated. Here, we describe studies on the mechanism of action of AdGABA. Using a combined approach of patch-clamp recordings and molecular biology we show that AdGABA inhibits Ca(2+) currents acting on Ca(V)α(2)δ only when applied chronically, both in a heterologous expression system and in dorsal root-ganglion neurons. AdGABA seems to require uptake and be acting intracellularly given that its effects are prevented by an inhibitor of the L-amino acid transport system. Interestingly, a mutation in the Ca(V)α(2)δ that abolishes GBP binding did not affect AdGABA actions, revealing that its mechanism of action is similar but not identical to that of GBP. These results indicate that AdGABA is an important Ca(V)α(2)δ ligand that regulates Ca(V) channels.
Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav-IPN), Mexico City, Mexico.
Elizabeth
E
Martínez-Hernández
Alejandro
A
Sandoval
Ricardo
R
González-Ramírez
Grigoris
G
Zoidis
Ricardo
R
Felix
D000218:Adamantane / Q000031:analogs & derivatives* / Q000494:pharmacology*; D027062:Amino Acid Transport System L / Q000502:physiology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D020864:Calcium Channels, N-Type / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D005727:Ganglia, Spinal; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000235:genetics; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives* / Q000494:pharmacology*
D027062:Amino Acid Transport System L; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D021122:Protein Subunits; D011994:Recombinant Proteins; D005680:gamma-Aminobutyric Acid; D000218:Adamantane