Interaction with cholesterol-rich membranes enhance the activity of the HIV inhibitor C34-cholesterol.

HOLLMANN A; MATOS, PM; CASTANHO MA; SANTOS NC

Alicante

Congreso; XII Iberian Peptide Meeting; 2012

Iberian peptide organization

The development of new drugs against the Human Immunodeficiency Virus type 1 (HIV-1) infection has been the focus of intense research. Although several drugs are now available, targeting different steps of the virus life cycle, due the appearance of resistances and the hope for more efficient drugs, this effort has not been slowed down yet. The fusion of the virus with the cell membrane and the consequent entry of the viral content into the target cell is a critical step of its life cycle. Efficiently blocking this process prevents all the subsequent intracellular steps, most importantly the integration of the viral genome, which can stay silent for years. It was recently demonstrated that the addition of cholesterol moiety to a classical HIV fusion inhibitor peptide, C34, dramatically increases its antiviral activity. The aim of present work was to evaluate the interaction of both derivatized and native C34 with biomembrane models, in order to explain this increase. Partition assays, using large unilamellar vesicles, demonstrate that C34-cholesterol is able to interact with several lipid mixtures, including cholesterol-rich membranes, in contrast with the unconjugated C34 peptide that present almost no interaction with lipids, except for DPPC. Surface pressures measurements on lipid monolayer were also carried out to confirm the absence of interaction between C34 and lipids, and to study the kinetic of C34-cholesterol incorporation on different lipids mixtures. Interactions with cholesterol-rich membranes, including lipid raft-mimicking membranes (POPC:Chol:SM in the same ratio), studied by fluorescence and surface pressure, confirm a higher affinity of C34-cholesterol toward these membranes, in contrast with the result obtained previously for enfuvirtide, a HIV-fusion inhibitor peptide already approved for clinical use. Taking into account that lipid rafts are considered as essential for the virus entry, the high partition of C34-cholesterol towards those domains is expected to make the drug more available at the sites where fusion occurs, as this intermediary membrane binding step can facilitate the drug delivery to the viral protein gp41 in its pre-fusion state. Quenching methodologies were used to evaluate the in-depth location of the Trp residues of the peptides inserted in POPC vesicles. Stearic acid molecules derivatized with doxyl (quencher) groups at carbon-5 (5NS) or -16 (16NS) were used. Fluorescence lifetime quenching data shows a mean shallow location at the membrane-water interface. Ultimately, the membrane can act as a ?catalyst? to the binding between gp41 and the peptide, as it has been proposed for other protein-ligand interactions on the membrane environment. Thus, for this case, the increased antiviral activity of of C34-cholesterol in relation to C34 and other HIV-fusion inhibitors seems to correlate with its higher affinity toward cholesterol-rich membrane domains.