Investigating the interactions of the 18 kDa translocator protein and its ligand PK11195 in planar lipid bilayers
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Date
2014-03
Journal Title
Journal ISSN
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Publisher
Elsevier
Abstract
The functional effects of a drug ligand may be due not only to an interaction with its membrane protein target, but also with the surrounding lipid membrane. We have investigated the interaction of a drug ligand, PK11195, with its primary protein target, the integral membrane 18 kDa translocator protein (TSPO), and model membranes using Langmuir monolayers, quartz crystal microbalance with dissipation monitoring (QCM-D) and neutron reflectometry (NR). We found that PK11195 is incorporated into lipid monolayers and lipid bilayers, causing a decrease in lipid area/molecule and an increase in lipid bilayer rigidity. NR revealed that PK11195 is incorporated into the lipid chain region at a volume fraction of ~ 10%. We reconstituted isolated mouse TSPO into a lipid bilayer and studied its interaction with PK11195 using QCM-D, which revealed a larger than expected frequency response and indicated a possible conformational change of the protein. NR measurements revealed a TSPO surface coverage of 23% when immobilised to a modified surface via its polyhistidine tag, and a thickness of 51 Å for the TSPO layer. These techniques allowed us to probe both the interaction of TSPO with PK11195, and PK11195 with model membranes. It is possible that previously reported TSPO-independent effects of PK11195 are due to incorporation into the lipid bilayer and alteration of its physical properties. There are also implications for the variable binding profiles observed for TSPO ligands, as drug–membrane interactions may contribute to the apparent affinity of TSPO ligands. © 2013, Elsevier B.V.
Description
Keywords
Ligands, Membrane proteins, Neutron reflectors, Lipids, Drugs, Crystals
Citation
Hatty, C. R., Le Brun, A. P., Lake, V., Clifton, L. A., Liu, G. J., James, M., & Banati, R. B. (2014). Investigating the interactions of the 18 kDa translocator protein and its ligand PK11195 in planar lipid bilayers. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1838(3), 1019-1030. doi:10.1016/j.bbamem.2013.12.013