Mitochondrial lipoic acid scavenging is essential for Plasmodium berghei liver stage development

Abstract

SummaryLipoic acid is an essential cofactor for enzymes that participate in key metabolic pathways in most organisms. While in mammalian cells lipoylated proteins reside exclusively in the mitochondria, apicomplexan parasites of the genus Plasmodium harbour two independent lipoylation pathways in the mitochondrion and the apicoplast, a second organelle of endosymbiotic origin. Protein lipoylation in the apicoplast relies on de novo lipoic acid synthesis while lipoylation of proteins in the mitochondrion depends on scavenging of lipoic acid from the host cell. Here, we analyse the impact of lipoic acid scavenging on the development of Plasmodium berghei liver stage parasites. Treatment of P. berghei-infected HepG2 cells with the lipoic acid analogue 8-bromo-octanoic acid (8-BOA) abolished lipoylation of mitochondrial enzyme complexes in the parasite while lipoylation of apicoplast proteins was not affected. Parasite growth as well as the ability of the parasites to successfully complete liver stage development by merosome formation were severely impaired but not completely blocked by 8-BOA. Liver stage parasites were most sensitive to 8-BOA treatment during schizogony, the phase of development when the parasite grows and undergoes extensive nuclear division to form a multinucleated syncytium. Live cell imaging as well as immunofluorescence analysis and electronmicroscopy studies revealed a close association of both host cell and parasite mitochondria with the parasitophorous vacuole membrane suggesting that host cell mitochondria might be involved in lipoic acid uptake by the parasite from the host cell.

The Host Endocytic Pathway is Essential for Plasmodium berghei Late Liver Stage Development

“…Recently, a close association between the PVM and the host mitochondria was suggested, a process thought to be important in the scavenging of lipoic acid by parasites (11). In this study, we establish that P. berghei parasites and the host endocytic pathway interact, and show that these interactions are www.traffic.dk 1351 A B C Figure 1: Plasmodium berghei liver parasites do not interact with compartments of the host early endocytic pathway.…”

Fatty acid metabolism in the Plasmodium apicoplast: Drugs, doubts and knockouts

“…The previous consensus was that lipoic acid metabolism in the apicoplast and mitochondrion were strictly compartmentalized, with the apicoplast lipoic acid synthesis pathway entirely responsible for lipoylation of the PDH complex, and the mitochondrial scavenging pathway wholly responsible for lipoylation of enzyme complexes in that organelle [80,82,83,85,159,160]. This view was supported by genetic and biochemical studies in Plasmodium and T. gondii, which demonstrated loss of FASII impacted only PDH lipoylation [45,165], and lipoic acid scavenged from the medium contributed uniquely to lipoylation of mitochondrial enzyme complexes [83,85]. However, in addition to decreasing PDH lipoylation, both the P. falciparum and P. berghei LipB knockouts displayed a lesser but significant reduction in the lipoylation of mitochondrial enzymes [84,164].…”

Sequestration of cholesterol within the host late endocytic pathway restricts liver-stagePlasmodiumdevelopment

“…Cholesterol is not the only lipid species obtained by the parasite from the host cell. Acquisition of both lipoic acid (Deschermeier et al ., 2012) and phosphatidylcholine (Itoe et al ., 2014) from the host environment is needed for robust liver-stage parasite growth. The latter is present in LE membranes but also in all other cellular membranes, so it seems unlikely that LEs and lysosomes would be the exclusive source of this lipid.…”