P‐glycoprotein modulates the fluidity gradient of the plasma membrane of multidrug resistant <scp>CHO</scp> cells

Cryo-electron microscopy has yielded high-resolution structural data of the multidrug efflux transporter P-glycoprotein (ABCB1), but its direct and indirect interactions within the native membrane environment have remained largely unexplored. Here, we compared the fluidity gradients of plasma membranes of the drug-sensitive CHO cell line AuxB1 and its P-glycoprotein overexpressing derivative B30 by fluorescence anisotropy of embedded n-(9-anthroyloxy) fatty acid probes (n = 2, 7, 9, 12, 16) in the temperature range of 10-50 °C. The shape of the temperature profiles of probe mobility was comparable in AuxB1 and B30 membranes, but did not match. Overexpression of P-glycoprotein smoothened the transversal gradient of the out-of-plane mode of rotation of the probes, which may facilitate the partitioning of hydrophobic drugs into the membrane and thereby increase the speed of P-glycoprotein to pump the drug out of the cell.