AFM Study of the Cytoskeletal Structures of Malaria Infected Erythrocytes

Abstract

Malaria is one of the severest human diseases on earth. It is caused by the asexual propagation of malaria parasites in host erythrocytes. During the process of maturation, parasites export parasite-expressed proteins, such as PfEMP1 and KHARP to the host cell membrane thus forming knobs on the host cell surface and thereby stiffening the membrane and causing cytoadherence (cell stickiness) to occur. To investigate the formation of knobs as well as the relationship between knobs and the host cell spectrin network, atomic force microscopy (AFM) is used to study both the extracellular and the cytoplasmic surface of infected erythrocyte membranes. Although the cytoskeletal structure can be observed from both the extracellular surface and cytoplasmic surface, the AFM images of cytoplasmic surface uncovered more details of the spectrin network. Knobs and their connections or linkages to the spectrin network were clearly observed from the cytoplasmic surface of infected erythrocytes. The size and distribution of knobs viewed from the cytoplasmic surface were similar to those observed from the extracellular surface. Furthermore, dramatic changes of spectrin network were detected after infection, i.e. the spectrin network is partially broken at the schizont stage. Altogether, our observation may help better understand the mechanisms of the structural and functional changes in malaria infection.KeywordsPlasmodium falciparumAtomic force microscopy (AFM)spectrin networkknobs