Plasmodium falciparum enolase complements yeast enolase functions and associates with the parasite food vacuole

Abstract

Plasmodium falciparum enolase (Pfeno) localizes to the cytosol, nucleus, cell membrane and cytoskeletal elements, suggesting multiple non-glycolytic functions for this protein. Our recent observation of association of enolase with the food vacuole (FV) in immuno-gold electron microscopic images of P. falciparum raised the possibility for yet another moonlighting function for this protein. Here we provide additional support for this localization by demonstrating the presence of Pfeno in purified FVs by immunoblotting. To examine the potential functional role of FV-associated Pfeno, we assessed the ability of Pfeno to complement a mutant Saccharomyces cervisiae strain deficient in enolase activity. In this strain (Tetr-Eno2), the enolase 1 gene is deleted and expression of the enolase 2 gene is under the control of a tetracycline repressible promoter. Enolase deficiency in this strain was previously shown to cause growth retardation, vacuolar fragmentation and altered expression of certain vacuolar proteins. Expression of Pfeno in the enolase-deficient yeast strain restored all three phenotypic effects. However, transformation of Tetr-eno2 with an enzymatically active, monomeric mutant form of Pfeno (Δ5Pfeno) fully restored cell growth, but only partially rescued the fragmented vacuolar phenotype, suggesting that the dimeric structure of Pfeno is required for the optimal vacuolar functions. Bioinformatic searches revealed the presence of Plasmodium orthologs of several yeast vacuolar proteins that are predicted to form complexes with Pfeno. Together, these observations raise the possibility that association of Pfeno with food vacuole in Plasmodium may have physiological function(s).

Comparison of an ELISA assay for the detection of adhesive/invasive Neospora caninum tachyzoites

“…The tetO region is a site with affinity for the TetR protein, which, once bound to the tetO site, blocks expression and is released from the site by tetracycline. This system is based on the E. coli tetracycline operon, which has been adapted for T. gondii and Plasmodium falciparum (DAS et al, 2011;MEISSNER et al, 2001MEISSNER et al, , 2002van POPPEL et al, 2006). However, only the β−galactosidase expression was employed in this study.…”

Food Vacuole Associated Enolase in Plasmodium Undergoes Multiple Post-Translational Modifications: Evidence for Atypical Ubiquitination

“…It catalyzes the inter-conversion of 2-phosphoglycerate and phosphoenolpyruvate during glycolysis and gluconeogenesis, respectively. Apart from its cytosolic localization, the presence of this protein has also been reported on the plasma membrane [1–6], nucleus [7–11] and vacuole [5,12,13]. This diverse sub-cellular distribution of enolase is likely to be associated with a variety of different functions, e.g.…”

“…Attempts were made to obtain insights into the functional role of food vacuole associated enolase in Plasmodium [13]. Involvement of enolase in vacuolar fusion and protein trafficking to vacuole have been reported in yeast [12].…”

“…The relative amounts of the three isoforms exhibit variation from preparation to preparation, suggesting the possibility of inter-conversion among the three variants in response to environmental or developmental cues [13]. As a first step towards understanding this phenomenon and to elucidate the vacuolar functions of enolase in Plasmodium , we decided to (i) analyze the food vacuolar proteome and identify the protein homologs of enolase interactors known in vacuoles from other organisms (e.g.…”

Papel do IP3 na transdução de sinal e função da heme oxigenase em Plasmodium falciparum.

“…A enolase de P. falciparum (Pfeno) pode ser encontrada no citossol, na membrana celular e no núcleo (Bhowmick et al, 2009;Das et al, 2011), sugerindo múltiplas funções para esta proteína. Ghosh et al (2011) reportaram que a enolase exportada na superfície do oocineto desempenha papel importante para a ativação do plasminogênio em plasmina (uma serina protease capaz de degradar as redes de fibrina do hospedeiro) o que permite a invasão do Plasmodium no trato intestinal do mosquito.…”