Abstract
BackgroundIn an earlier study, it was observed that the vaccination with Plasmodium falciparum enolase can confer partial protection against malaria in mice. Evidence has also build up to indicate that enolases may perform several non-glycolytic functions in pathogens. Investigating the stage-specific expression and sub-cellular localization of a protein may provide insights into its moonlighting functions.MethodsSub-cellular localization of P. falciparum enolase was examined using immunofluorescence assay, immuno-gold electron microscopy and western blotting.ResultsEnolase protein was detected at every stage in parasite life cycle examined. In asexual stages, enolase was predominantly (≥85–90%) present in soluble fraction, while in sexual stages it was mostly associated with particulate fraction. Apart from cytosol, enolase was found to be associated with nucleus, food vacuole, cytoskeleton and plasma membrane.ConclusionDiverse localization of enolase suggests that apart from catalyzing the conversion of 2-phosphoglycericacid into phosphoenolpyruvate in glycolysis, enolase may be involved in a host of other biological functions. For instance, enolase localized on the merozoite surface may be involved in red blood cell invasion; vacuolar enolase may be involved in food vacuole formation and/or development; nuclear enolase may play a role in transcription.
Highlights
In an earlier study, it was observed that the vaccination with Plasmodium falciparum enolase can confer partial protection against malaria in mice
Enolase staining in these cells showed a punctuate pattern where particulate enolase appears to be present beneath the plasma membrane, which is quite distinct from the homogenous staining observed for circum sporozoite protein (CSP)
Large scale stage specific analysis of P. falciparum proteome has shown that the enolase is expressed in all stages (Trophozoite, schizont, merozoite, gametocyte) in the life cycle of the parasite [44,45] and was associated with the host cell plasma membrane of the infected red blood cells [41]
Summary
It was observed that the vaccination with Plasmodium falciparum enolase can confer partial protection against malaria in mice. Evidence has build up to indicate that enolases may perform several non-glycolytic functions in pathogens. Glycolytic enzymes have been shown to perform nonglycolytic functions in apicomplexan parasites. Glyceraldehydes 3-phosphate dehydrogenase (GAPDH) has been shown to perform certain non-glycolytic functions in P. falciparum [17]. Due to their importance in Plasmodium for energy production and other physiological functions, glycolytic enzymes have been termed as important therapeutic targets and validated in the new large scale ventures for anti-malarials [12,18,19,20,21]
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