Calcium influx in Trypanosoma brucei can be induced by amphiphilic peptides and amines

Cupiennin 1a exhibits a remarkably broad, non-stereospecific cytolytic activity on bacteria, protozoan parasites, insects, and human cancer cells

“…These might also contribute to the electrostatic attraction of the peptides. Incubation of T. brucei with melittin, a cytolytic peptide isolated from honey bee venom in submicromolar concentrations, resulted in a calcium influx into the parasites without disrupting cell permeability, which only occurs at higher concentrations (Ruben et al 1996). Our results also support other reports concerning the trypanocidal activity of several antimicrobially acting peptides of diverse origin which act by disrupting membrane integrity (Boulanger et al 2002;Kitani et al 2009;Löfgren et al 2008;McGwire et al 2003;Yamage et al 2009).…”

Hyperosmotic Stress Induces Aquaporin-dependent Cell Shrinkage, Polyphosphate Synthesis, Amino Acid Accumulation, and Global Gene Expression Changes in Trypanosoma cruzi

“…We confirmed that the plasma membrane remained intact during the hyperosmotic stress by performing the same experiment in the presence of extracellular ethidium bromide (EtBr). Because EtBr exhibits a fluorescence enhancement upon binding DNA, a compromise in membrane integrity would result in increased fluorescence (17). No significant increase in EtBr fluorescence could be observed during the induction of hyperosmotic stress (Fig.…”

“…Membrane Integrity-Following the induction of hyposmotic or hyperosmotic stress, membrane integrity was determined by ethidium bromide exclusion (17). Briefly, aliquots of cells were placed in isosmotic buffer containing 50 M ethidium bromide and hyposmotic or hyperosmotic stress was induced as described above.…”

Selective Transfer of Calcium from an Acidic Compartment to the Mitochondrion of Trypanosoma brucei

“…To evaluate Ca 2ϩ transport properties of the mitochondrion in intact cells, Ca 2ϩ homeostasis was disrupted in two distinct ways: either by influx across the plasma membrane or by release from intracellular pools. Melittin is an amphiphilic peptide that causes Ca 2ϩ to selectively enter the cell across the plasma membrane of T. brucei bloodstream forms (28). When procyclic cells were treated with 200 nM melittin, the pCYT-AEQ transformants show an immediate spike (possibly an injection artifact), followed by a transient elevation from the resting level of Ca 2ϩ to 1.2 Ϯ 0.4 M (n ϭ 16) (Fig.…”