Physicochemical Aspects of the Plasmodium chabaudi-Infected Erythrocyte

Abstract

Membrane electrochemical potential is a feature of the molecular profile of the cell membrane and the two-dimensional arrangement of its charge-bearing molecules. Plasmodium species, the causative agents of malaria, are intracellular parasites that remodel host erythrocytes by expressing their own proteins on erythrocyte membranes. Although various aspects of the modifications made to the host erythrocyte membrane have been extensively studied in some human Plasmodium species (such as Plasmodium falciparum), details of the structural and molecular biological modifications made to host erythrocytes by nonhuman Plasmodium parasites have not been studied. We employed zeta potential analysis of erythrocytes parasitized by P. chabaudi, a nonhuman Plasmodium parasite. From these measurements, we found that the surface potential shift was more negative for P. chabaudi-infected erythrocytes than for P. falciparum-infected erythrocytes. However, electron microscopic analysis of the surface of P. chabaudi-infected erythrocytes did not reveal any modifications as compared with nonparasitized erythrocytes. These results suggest that differences in the membrane modifications found herein represent unique attributes related to the pathogenesis profiles of the two different malaria parasite species in different host animals and that these features have been acquired through parasite adaptations acquired over long evolutionary time periods.

Figure 1

Nonparasitized mouse control erythrocyte (a, b). Electron micrographs of P. chabaudi-infected erythrocytes (c, d), showing the lack of any raised structures on the erythrocyte surface. In contrast, many knob-like structures on the surface of a P. falciparum-infected human erythrocyte are apparent (g). Electron micrograph illustrating the very smooth surface of a nonparasitized human erythrocyte (e). (a, c, e, g) SEM and (b, d, f, h) TEM. Bar = 1.0 μm (a, c, e, g) and 500 nm (b, d, f, h).

Figure 2

Z-potential data for nonparasitized (a) and P. chabaudi-parasitized (≈30–48% parasitemia) with nonparasitized (≈52–70%) (b) mouse erythrocytes. The membrane potential increased to a more negative value in the P. chabaudi-infected erythrocytes compared with the uninfected erythrocyte controls.

Figure 3

(a) and (b) represent a western blot comparison of the DRM fraction, which influences the raft domain, between nonparasitized and parasitized mouse erythrocytes, respectively. Flotillin-1 was used as a reference raft marker (MW = 48 kD).