Computational Pharmacogenetics of P-Glycoprotein Mediated Antiepileptic Drug Resistance

The treatment of epilepsy using antiepileptogenic drugs is complicated by drug resistance, resulting in treatment failure in more than one-third of cases. Human P-glycoprotein (hPGP;MDR1) is a known epileptogenic mediator.Given that experimental investigations have suggested a role for pharmacogenetics in this treatment failure, it would be of interest to study hPGP polymorphisms that might contribute to the emergence of drug resistance. Changes in protein functional activity could result from mutations as well as altered abundance. Bioinformatics approaches were used to assess and rank the functional impact of 20 missenseMDR1polymorphisms and the top five were selected. The structures of the wildtype and variant hPGP were modelled based on the mouse PGP structure. Docking studies of the wildtype and variant hPGP with four standard anti-epileptic drugs were carried out.Our results revealed that the drug binding site with respect to the wildtype protein was uniform. However, the variant hPGP proteins displayed a repertoire of binding sites with stronger binding affinities towards the drug.Our studies indicated that specific polymorphisms inMDR1could drive conformational changes of PGP structure, facilitating altered contacts with drug-substrates and thus modifying their bioavailability. This suggests thatMDR1polymorphisms could actively contribute to the emergence of pharmaco-resistance in antiepileptic therapy.