pgp - publications

Predict more pgp - ligand interactions now!

1. Biochemistry. 2012 Feb 24. [Epub ahead of print]

Evidence for modulatory sites at the lipid-protein interface of the human
multidrug transporter P-glycoprotein.

Mandal D, Moitra K, Ghosh D, Xia D, Dey S.

The human multidrug transporter P-glycoprotein (Pgp or ABCB1) sets up
pharmacological barriers to many clinically important drugs, a therapeutic remedy
for which is yet to be formulated. For rational design of mechanism-based
inhibitors (or modulators), it is necessary to map the potential sites for
modulator interaction and understand their modes of communication with the other
functional domains of Pgp. In this study, combining directed mutagenesis with
homology modeling we provide evidence for two modulator-specific sites at the
lipid protein interface of Pgp. Targeting 21 variant positions in the
COOH-terminal transmembrane (TM) regions, we find residues M948 (in TM11), F983,
M986, V988 and Q990 (all four in TM12) critically involved in substrate-site
modulation by a thioxanthene-based allosteric modulator cis-(Z)-flupentixol.
Interestingly, for ATP-site modulation by the same modulator, only two (M948 and
Q990) out of those four residues appear indispensable, together with two
additional residues T837 and I864 in TM9 and TM10 respectively, suggesting
independent modes of communication linking the allosteric site with the
substrate-binding and the ATPase domains. None of the 7 identified residues
identified prove critical for modulation of the substrate- or the ATP- sites by
Pgp modulators that get transported by the pump, such as cyclosporin A or
verapamil, indicating their specificity for cis-(Z)-flupentixol. On the other
hand, ATP-site modulation by verapamil proves highly sensitive to replacement at
positions F716 (in TM7) and I765 (in TM8), and to a more moderate extent at I764
and L772 (both in TM8). Homology modeling based on the known crystal structures
of the bacterial multidrug transporter SAV1866 and the mouse Pgp homolog maps the
identified residues primarily at the lipid-protein interface of Pgp, in two
spatially distinct modulator-specific clusters. The two modulatory sites
demonstrate negative synergism in influencing ATP hydrolysis consolidating their
spatial distinctness. Since Pgp is known to recruit drug molecules directly from
the lipid bilayer, identification of modulatory sites at the lipid-protein
interface and at the same time outside the conventional central drug-binding
cavity is mechanistically revealing.

PMID: 22360349 [PubMed - as supplied by publisher]