Plasmodium falciparum: Nitric oxide modulates heme speciation in isolated food vacuoles

Abstract

Nitric oxide (NO) and NO-derived reactive nitrogen species (RNS) are present in the food vacuole (FV) of P. falciparum trophozoites. The product of PFL1555w, a putative cytochrome b5, localizes in the FV membrane, similar to what was previously observed for the product of PF13_0353, a putative cytochrome b5 reductase. These two gene products may contribute to NO generation by denitrification chemistry from nitrate and/or nitrite present in the erythrocyte cytosol. The possible coordination of NO to heme species present in the food vacuole was probed by resonance Raman spectroscopy. The spectroscopic data revealed that in situ generated NO interacts with heme inside the intact FVs to form ferrous heme nitrosyl complexes that influence intra-vacuolar heme solubility. The formation of heme nitrosyl complexes within the FV is a previously unrecognized factor that could affect the equilibrium between soluble and crystallized heme within the FV in vivo.

Digital phantoms generated by spectral and spatial light modulators

“…[18][19][20] The spectral signatures of the hemozoin have been studied by conventional spectroscopic techniques such as Fourier transform infrared and Raman spectroscopy. [20][21][22] These conventional spectroscopic studies are based on cuvette measurements of pure substances extracted from the cells. On the other hand, neither sample extraction nor a priori knowledge of the content of substances is necessary for identifying the substances by hyperspectral imaging and analysis.…”

Protein S-nitrosylation in Plasmodium falciparum

“…By using a specific probe, RNS have been detected in ring and trophozoite stages of P. falciparum as well as in the parasite gametocyte (37). Although P. falciparum seems to lack an NOS ortholog, it has been suggested that it probably produces NO from a nitrate/nitrite reduction pathway (37,38).…”

Sequestration and metabolism of host cell arginine by the intraerythrocytic malaria parasitePlasmodium falciparum

“…Ghigo et al reported that the intraerythrocytic parasite itself can synthesize NO, based on measurements of citrulline production (Ghigo et al, 1995). More recently, it was reported that there is, in the parasite, a pool of NO localized to the digestive vacuole (Ostera et al, 2008); however, no citrulline production was detected, and it was proposed that the parasite's NO pool is maintained not by a NOS but by the ingestion of host cell cytosol and the subsequent conversion of host nitrate to NO by an unknown parasite nitrate reductase (Ostera et al, 2008;Ostera et al, 2011). By contrast, Rey and colleagues reported that there to be an NO pool present throughout the parasite, sustained by an arginine-dependent pathway (Rey et al, 2014).…”