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Association of Plasmodium berghei proteins with the host erythrocyte membrane: binding to inside-out vesicles
M F Wiser1, A C Sartorelli, C L Patton
1MacArthur Center for Molecular Parasitology, Yale University School of Medicine, New Haven, CT.
Abstract:
Two acidic phosphoproteins of Plasmodium berghei origin, of 65 and 46 kDa, are associated with the plasma membrane of the host mouse erythrocyte. The 65-kDa protein partitions between a soluble and particulate phase upon host cell lysis, whereas the 46-kDa protein is localized exclusively in the particulate fraction. Both proteins bind to inside-out vesicles derived from erythrocyte ghosts and the conditions of the reassociation reaction indicate that the binding is specific and that the proteins interact only with the cytoplasmic face of the erythrocyte membrane. The 65-kDa protein appears to exist in two membrane-associated states; one loosely bound, which readily dissociates from the membrane, and a more tightly associated state, which does not dissociate under non-denaturing conditions. The 46-kDa protein is tightly bound to the host erythrocyte membrane and does not dissociate. Cross-linking studies suggest that both of these parasite proteins interact with the submembrane cytoskeleton of the erythrocyte, and that the 65-kDa protein also appears to interact simultaneously with the lipid bilayer and erythrocyte membrane proteins. However, direct interaction between the malarial proteins and distinct erythrocyte membrane proteins could not be demonstrated. In summary, these findings indicate that the acidic phosphoproteins of the malarial parasite interact with the cytoplasmic face of the erythrocyte membrane both in vivo and in vitro.
Insights
Two Plasmodium berghei phosphoproteins interact with the host erythrocyte membrane. These malarial proteins bind to the cytoplasmic face, associating with the cytoskeleton and membrane bilayer.
Area of Science:
- Parasitology
- Cell Biology
- Biochemistry
Background:
- Plasmodium berghei, a malaria-causing parasite, infects host erythrocytes.
- Parasite proteins associated with the host cell membrane are crucial for infection.
- Understanding these interactions is key to developing anti-malarial strategies.
Purpose of the Study:
- To investigate the association of two Plasmodium berghei acidic phosphoproteins (65 and 46 kDa) with the host mouse erythrocyte membrane.
- To determine the localization and binding characteristics of these parasite proteins.
- To elucidate the nature of their interaction with the erythrocyte membrane components.
Main Methods:
- Erythrocyte lysis and fractionation to isolate membrane-associated proteins.
- Reassociation experiments with inside-out erythrocyte vesicles.
- Analysis of protein binding under various conditions (soluble/particulate phases, dissociation).
- Cross-linking studies to identify interacting host cell components.
Main Results:
- Both 65 and 46 kDa phosphoproteins are associated with the host erythrocyte plasma membrane.
- The 46 kDa protein is exclusively in the particulate fraction, while the 65 kDa protein partitions between soluble and particulate phases.
- Proteins bind specifically to the cytoplasmic face of the erythrocyte membrane.
- The 65 kDa protein exhibits two binding states (loose and tight), while the 46 kDa protein is tightly bound.
- Cross-linking suggests interaction with the submembrane cytoskeleton and potentially the lipid bilayer/membrane proteins for the 65 kDa protein.
Conclusions:
- Acidic phosphoproteins from Plasmodium berghei interact with the cytoplasmic face of the host erythrocyte membrane.
- These interactions involve specific binding and association with the erythrocyte's submembrane cytoskeleton.
- The findings provide insights into the molecular mechanisms of malaria parasite-host cell interactions.