The Plasma Membrane of Bloodstream-form African Trypanosomes Confers Susceptibility and Specificity to Killing by Hydrophobic Peptides

Abstract

Trypanosoma brucei is the causative agent of both a veterinary wasting disease and human African trypanosomiasis, or sleeping sickness. The cell membrane of the developmental stage found within the mammalian host, the bloodstream form (BSF), is highly dynamic, exhibiting rapid rates of endocytosis and lateral flow of glycosylphosphatidylinositol-anchored proteins. Here, we show that the cell membrane of these organisms is a target for killing by small hydrophobic peptides that increase the rigidity of lipid bilayers. Specifically, we have derived trypanocidal peptides that are based upon the hydrophobic N-terminal signal sequences of human apolipoproteins. These peptides selectively partitioned into the plasma membrane of BSF trypanosomes, resulting in an increase in the rigidity of the bilayer, dramatic changes in cell motility, and subsequent cell death. No killing of the developmental stage found within the insect midgut, the procyclic form, was observed. Additionally, the peptides exhibited no toxicity toward mammalian cell lines and did not induce hemolysis. Studies with model liposomes indicated that bilayer fluidity dictates the susceptibility of membranes to manipulation by hydrophobic peptides. We suggest that the composition of the BSF trypanosome cell membrane confers a high degree of fluidity and unique susceptibility to killing by hydrophobic peptides and is therefore a target for the development of trypanocidal drugs.

A Retained Secretory Signal Peptide Mediates High Density Lipoprotein (HDL) Assembly and Function of Haptoglobin-related Protein

“…These data are consistent with our previous findings for Hpr-SP (13) and indicate that it is indeed lipid fluidity that dictates sensitivity to interaction with Hpr rather than a specific binding to certain acyl chains.…”

“…Liposome Permeabilization Assays-Calcein release assays were performed as described in detail previously (13,15,16). Liposomes were extruded above the transition temperature of the component lipids and used immediately to limit the leakage of entrapped dye due to potential changes in phase.…”

Cellular FRET-Biosensors to Detect Membrane Targeting Inhibitors of N-Myristoylated Proteins

“…It is even conceivable to implement the biosensors in protozoan pathogens, e.g. in order to understand the mechanism of action of membrane organization disrupting compounds [34], [52].…”

Novel African Trypanocidal Agents: Membrane Rigidifying Peptides

“…Specificity of SHP is mediated by a high degree of fluidity in the plasma membrane of BSF cells [10]. These peptides do not bind, and thus do not kill, PCF T. brucei , which has a more rigid plasma membrane.…”