Transport Across Cell Membranes is Modulated by Lipid Order

This study measures the uptake of various dyes into HeLa cells and determines simultaneously the degree of membrane lipid chain order on a single cell level by spectral analysis of the membrane-embedded dye Laurdan. First, this study finds that the mean generalized polarization (GP) value of single cells varies within a population in a range that is equivalent to a temperature variation of 9 K. This study exploits this natural variety of membrane order to examine the uptake as a function of GP at constant temperature. It is shown that transport across the cell membrane correlates with the membrane phase state. Specifically, higher membrane transport with increasing lipid chain order is observed. As a result, hypothermal-adapted cells with reduced lipid membrane order show less transport. Environmental factors influence transport as well. While increasing temperature reduces lipid order, it is found that locally high cell densities increase lipid order and in turn lead to increased dye uptake. To demonstrate the physiological relevance, membrane state and transport during an in vitro wound healing process are analyzed. While the uptake within a confluent cell layer is high, it decreases toward the center where the membrane lipid chain order is lowest.

Automated summary

This study measures dye uptake in HeLa cells and determines membrane lipid chain order on single cell level using spectral analysis of Laurdan. The study finds that the membrane order affects transport across the cell membrane, with higher lipid chain order leading to increased transport. Environmental factors, such as temperature and cell density, also influence transport. In addition, the study analyzes membrane state and transport during in vitro wound healing, showing that uptake decreases with lower membrane lipid chain order.