# P‐glycoprotein modulates the fluidity gradient of the plasma membrane of multidrug resistant CHO cells

## TL;DR

This study shows that P-glycoprotein affects the fluidity of cell membranes, which may help multidrug-resistant cells pump out drugs more efficiently.

## Contribution

The study reveals how P-glycoprotein modulates membrane fluidity gradients in multidrug-resistant cells.

## Key findings

- P-glycoprotein overexpression smoothened the transversal fluidity gradient in cell membranes.
- This change may enhance the partitioning of hydrophobic drugs into the membrane.
- It could increase the speed at which P-glycoprotein expels drugs from the cell.

## Abstract

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.

To explore the impact of the overexpression of the multidrug‐transporter P‐glycoprotein (ABCB1) on membrane fluidity, we compared the transversal gradient of mobility and microviscosity in plasma membranes of drug‐sensitive Chinese hamster ovary cells (AuxB1) and their multidrug‐resistant derivatives (B30) using the fluorescent n‐(9‐anthroyloxy) fatty acid probes (n = 2, 7, 9, 12, 16) as molecular rulers.