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Erythrocyte detergent-resistant membrane proteins: their characterization and selective uptake during malarial
Sean C Murphy1, Benjamin U Samuel, Travis Harrison
1Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
Abstract:
Infection of human erythrocytes by the apicomplexan malaria parasite Plasmodium falciparum results in endovacuolar uptake of 4 host proteins that reside in erythrocyte detergent-resistant membranes (DRMs). Whether this vacuolar transport reflects selective uptake of host DRM proteins remains unknown. A further complication is that DRMs of vastly different protein and cholesterol contents have been isolated from erythrocytes. Here we show that isolated DRMs containing the highest cholesterol-to-protein ratio have low protein mass. Liquid chromatography, mass spectrometry, and antibody-based studies reveal that the major DRM proteins are band 3, flotillin-1 and -2, peroxiredoxin-2, and stomatin. Band 3 and stomatin, which reflect the bulk mass of erythrocyte DRM proteins, and all tested non-DRM proteins are excluded from the vacuolar parasite. In contrast, flotillin-1 and -2 and 8 minor DRM proteins are recruited to the vacuole. These data suggest that DRM association is necessary but not sufficient for vacuolar recruitment and there is active, vacuolar uptake of a subset of host DRM proteins. Finally, the 10 internalized DRM proteins show varied lipid and peptidic anchors indicating that, contrary to the prevailing model of apicomplexan vacuole formation, DRM association, rather than lipid anchors, provides the preferred criteria for protein recruitment to the malarial vacuole.
Insights
The malaria parasite Plasmodium falciparum selectively internalizes specific host erythrocyte membrane proteins into its vacuole. This selective uptake is linked to detergent-resistant membrane (DRM) association, not lipid anchors.
Area of Science:
- Cell Biology
- Parasitology
- Biochemistry
Background:
- The malaria parasite Plasmodium falciparum infects human erythrocytes, leading to the uptake of host proteins into its vacuole.
- It is unclear if this uptake is selective for host proteins residing in detergent-resistant membranes (DRMs).
- Erythrocyte DRMs exhibit variability in protein and cholesterol content.
Purpose of the Study:
- To investigate the selective uptake of host erythrocyte proteins by Plasmodium falciparum.
- To determine the role of detergent-resistant membrane (DRM) association in protein recruitment to the parasite vacuole.
Main Methods:
- Isolation and characterization of erythrocyte DRMs.
- Liquid chromatography and mass spectrometry to identify DRM proteins.
- Antibody-based studies to confirm protein localization and uptake.
Main Results:
- Isolated DRMs with high cholesterol-to-protein ratios had low protein mass.
- Major DRM proteins include band 3, flotillin-1, flotillin-2, peroxiredoxin-2, and stomatin.
- Flotillin-1, flotillin-2, and 8 minor DRM proteins were recruited to the parasite vacuole, while band 3, stomatin, and non-DRM proteins were excluded.
- Internalized DRM proteins exhibited diverse lipid and peptidic anchors.
Conclusions:
- DRM association is necessary but not sufficient for vacuolar recruitment of host proteins.
- Plasmodium falciparum actively and selectively internalizes a subset of host DRM proteins.
- DRM association, rather than lipid anchors, is the primary criterion for protein recruitment to the malarial vacuole, challenging existing models.