Cholesterol, lanosterol, and ergosterol attenuate the membrane association of LL-37(W27F) and temporin L.

Sterols impart significant changes to the biophysical properties of lipid bilayers. In this regard the impact of cholesterol on membrane organization and dynamics is particularly well documented and serves for comparison with other sterols. However, the factors underlying the molecular evolution of cholesterol remain enigmatic. To this end, cholesterol attenuates membrane perturbation by the so-called antimicrobial peptides (AMPs), produced ubiquitously by eukaryotic cells to combat bacterial infections by compromising the permeability barrier function of the microbial target membranes. In the present study, we addressed the effects of cholesterol, ergosterol, and lanosterol on the membrane association of two structurally and functionally diverse AMPs viz. LL-37(F27W) and temporin L (TemL) using fluorescence spectroscopy. Interestingly, sterol concentration dependent effects on the membrane association of these peptides were observed. At X(Sterol)=0.5 cholesterol was most effective in reducing the membrane intercalation of both LL-37(F27W) and TemL, the corresponding efficiencies of the three sterols decreasing as cholesterol>lanosterol> or =ergosterol, and cholesterol>lanosterol>ergosterol. It is conceivable that part of the selection pressure for the chemical evolution of cholesterol may have derived from the ability to protect the AMP-secreting host cell from the membrane damaging action of the antimicrobial peptides.