Glycolytic enzymes form membrane-less condensates in the malaria parasite Plasmodium falciparum by sensing glucose levels

Abstract

Recent studies have shown that liquid-liquid phase separation (LLPS) in cells can regulate essential cellular events, including metabolic processes. Glycolytic bodies (G-bodies) are biomolecular condensates formed through the LLPS of glycolytic enzymes, and they accelerate glycolysis to overcome hypoxic stress in several organisms. Although the asexual blood stage (ABS) of the human malaria parasite Plasmodium falciparum highly depends on glycolysis for energy production, there have been no reports of the formation of such G-bodies throughout the parasites lifecycle. Using fluorescence tagging and live imaging, we found that G-body-like condensates containing phosphofructokinase 9 (PFK9) and phosphoglycerate kinase (PGK) were formed in the parasite cells after long-term culture under conditions of low glucose. These G-body-like structures appeared stable, but membrane staining and osmotic stress experiments suggested that the observed condensates were not associated with lipid membrane. Further microscopic observations and mathematical analyses of high signal-to-noise ratio images indicated that small condensates were formed transiently first, and these then gradually grew and stabilized in the cytosol. These results suggested that the formation of glycolytic enzyme condensates may be an important cellular response for adapting to blood sugar level oscillations in the host and maintaining the parasites multiplication in the ABS. Significance statementGlycolytic bodies (G-bodies), which are biomolecular condensates formed through the liquid-liquid phase separation of glycolytic enzymes, can accelerate glycolysis to produce energy and overcome hypoxic stress. The parasites that cause malaria depend on glycolysis for energy production, but there have been no reports that these parasites form G-bodies. We demonstrated that membrane-less G-body-like structures formed in media containing low levels of glucose. Small condensates appeared first and over time, the condensates became larger and more stable. The formation of glycolytic enzyme condensates may be important for the malaria parasite to adapt to fluctuating blood sugar levels in the host. These results further our understanding of the cellular mechanisms for the survival of malaria parasites.