Label‐free surface‐enhanced Raman spectroscopy of lipid‐rafts from hepatocyte plasma membranes

Abstract

Lipid rafts are sphingomyelin/cholesterol‐rich domains present in the plasma membrane of eukaryotic cells. In the hepatocyte, it has been shown that these domains intervene and modify a wide range of functions from which cell signaling in health and disease is of major importance. The present investigation proposes a novel strategy for the study of plasma membrane lipid rafts using surface‐enhanced Raman spectroscopy (SERS) and spectra processing employing the principal component analysis (PCA) in correlation with conventional biochemical techniques. SERS has been used for artificial membranes; our approach has the advantage that allows studying purified biological membranes using small volumes of biological samples and a very simple protocol. Therefore, the use of SERS/PCA represents an important advantage for the study not only of the structure and composition of biological membranes but also for the understanding of the functions carried by the membrane‐embedded proteins. Our work using SERS/PCA for the first time shows a correlation when studying the composition of lipid rafts from the cell plasma membrane and the catalytic activity of the Ca2+‐ATPase, and its direct association with the presence of specific lipids located in membrane lipid rafts. Also, we show that changes in plasma membrane and the catalytic activity of the Ca2+‐ATPase activity present in the plasma membrane of hepatocytes after partial depletion of membrane cholesterol carried out by methyl‐beta‐cyclodextrin correlate with the changes in the enzyme activity and the presence of cholesterol‐rich domains of lipid rafts. Copyright © 2017 John Wiley & Sons, Ltd.