Disruption of the Life Cycle through Transcriptional Reprogramming by Inhibitors of Jumonji Demethylases.

Little is known about the role of the three Jumonji C (JmjC) enzymes in (). Here, we show that JIB-04 and other established inhibitors of mammalian JmjC histone demethylases kill asexual blood stage parasites and are even more potent at blocking gametocyte development and gamete formation. In late stage parasites, JIB-04 increased levels of trimethylated lysine residues on histones, suggesting the inhibition of Jumonji demethylase activity.

A mevalonate bypass system facilitates elucidation of plastid biology in malaria parasites.

Malaria parasites rely on a plastid organelle for survival during the blood stages of infection. However, the entire organelle is dispensable as long as the isoprenoid precursor, isopentenyl pyrophosphate (IPP), is supplemented in the culture medium. We engineered parasites to produce isoprenoid precursors from a mevalonate-dependent pathway, creating a parasite line that replicates normally after the loss of the apicoplast organelle.

Host biotin is required for liver stage development in malaria parasites.

Acetyl-CoA carboxylase (ACC) is a biotin-dependent enzyme that is the target of several classes of herbicides. Malaria parasites contain a plant-like ACC, and this is the only protein predicted to be biotinylated in the parasite. We found that ACC is expressed in the apicoplast organelle in liver- and blood-stage malaria parasites; however, it is activated through biotinylation only in the liver stages.

A novel lipoate attachment enzyme is shared by Plasmodium and Chlamydia species.

Lipoate is an essential cofactor for enzymes that are important for central metabolism and other processes. In malaria parasites, scavenged lipoate from the human host is required for survival. The Plasmodium falciparum mitochondrion contains two enzymes (PfLipL1 and PfLipL2) that are responsible for activating mitochondrial proteins through the covalent attachment of lipoate (lipoylation).

Redox-dependent lipoylation of mitochondrial proteins in Plasmodium falciparum.

Lipoate scavenging from the human host is essential for malaria parasite survival. Scavenged lipoate is covalently attached to three parasite proteins: the H-protein and the E2 subunits of branched chain amino acid dehydrogenase (BCDH) and α-ketoglutarate dehydrogenase (KDH). We show mitochondrial localization for the E2 subunits of BCDH and KDH, similar to previously localized H-protein, demonstrating that all three lipoylated proteins reside in the parasite mitochondrion.

The suf iron-sulfur cluster synthesis pathway is required for apicoplast maintenance in malaria parasites.

The apicoplast organelle of the malaria parasite Plasmodium falciparum contains metabolic pathways critical for liver-stage and blood-stage development. During the blood stages, parasites lacking an apicoplast can grow in the presence of isopentenyl pyrophosphate (IPP), demonstrating that isoprenoids are the only metabolites produced in the apicoplast which are needed outside of the organelle. Two of the isoprenoid biosynthesis enzymes are predicted to rely on iron-sulfur (FeS) cluster cofactors, however, little is known about FeS cluster synthesis in the parasite or the roles that FeS cluster proteins play in parasite biology.

A key role for lipoic acid synthesis during Plasmodium liver stage development.

The successful navigation of malaria parasites through their life cycle, which alternates between vertebrate hosts and mosquito vectors, requires a complex interplay of metabolite synthesis and salvage pathways. Using the rodent parasite Plasmodium berghei, we have explored the synthesis and scavenging pathways for lipoic acid, a short-chain fatty acid derivative that regulates the activity of α-ketoacid dehydrogenases including pyruvate dehydrogenase. In Plasmodium, lipoic acid is either synthesized de novo in the apicoplast or is scavenged from the host into the mitochondrion.

Plasmodium falciparum apicoplast transit peptides are unstructured in vitro and during apicoplast import.

Trafficking of soluble proteins to the apicoplast in Plasmodium falciparum is determined by an N-terminal transit peptide (TP) which is necessary and sufficient for apicoplast import. Apicoplast precursor proteins are synthesized at the rough endoplasmic reticulum, but are then specifically sorted from other proteins in the secretory pathway. The mechanism of TP recognition is presently unknown.

Activation of sterol regulatory element binding proteins in the absence of Scap in Drosophila melanogaster.

The escort factor Scap is essential in mammalian cells for regulated activation of sterol regulatory element binding proteins (SREBPs). SREBPs are membrane-bound transcription factors. Cells lacking Scap cannot activate SREBP.

Activation of sterol regulatory element-binding protein by the caspase Drice in Drosophila larvae.

During larval development in Drosophila melanogaster, transcriptional activation of target genes by sterol regulatory element-binding protein (dSREBP) is essential for survival. In all cases studied to date, activation of SREBPs requires sequential proteolysis of the membrane-bound precursor by site-1 protease (S1P) and site-2 protease (S2P). Cleavage by S2P, within the first membrane-spanning helix of SREBP, releases the transcription factor.

Alternative processing of sterol regulatory element binding protein during larval development in Drosophila melanogaster.

Sterol regulatory element binding protein (SREBP) is a major transcriptional regulator of lipid metabolism. Nuclear Drosophila SREBP (dSREBP) is essential for larval development in Drosophila melanogaster but dispensable in adults. dSREBP(-) larvae die at second instar owing to loss of dSREBP-mediated transcription but survive to adulthood when fed fatty acids.

Fatty acid auxotrophy in Drosophila larvae lacking SREBP.

SREBPs are membrane bound transcription factors that are crucial for normal lipid synthesis in animal cells. Here, we show that Drosophila lacking dSREBP die before the third larval instar. Mutant larvae exhibit pronounced growth defects prior to lethality, along with substantial deficits in the transcription of genes required for fatty acid synthesis.