title: The role of neutral lipid nanospheres in Plasmodium falciparum haem crystallization.
abstract: The intraerythrocytic malaria parasite constructs an intracellular haem crystal, called haemozoin, within an acidic digestive vacuole where haemoglobin is degraded. Haem crystallization is the target of the widely used antimalarial quinoline drugs. The intracellular mechanism of molecular initiation of haem crystallization, whether by proteins, polar membrane lipids or by neutral lipids, has not been fully substantiated. In the present study, we show neutral lipid predominant nanospheres, which envelop haemozoin inside Plasmodium falciparum digestive vacuoles. Subcellular fractionation of parasite-derived haemozoin through a dense 1.7 M sucrose cushion identifies monoacylglycerol and diacylglycerol neutral lipids as well as some polar lipids in close association with the purified haemozoin. Global MS lipidomics detects monopalmitic glycerol and monostearic glycerol, but not mono-oleic glycerol, closely associated with haemozoin. The complex neutral lipid mixture rapidly initiates haem crystallization, with reversible pH-dependent quinoline inhibition associated with quinoline entry into the neutral lipid microenvironment. Neutral lipid nanospheres both enable haem crystallization in the presence of high globin concentrations and protect haem from H2O2 degradation. Conceptually, the present study shifts the intracellular microenvironment of haem crystallization and quinoline inhibition from a polar aqueous location to a non-polar neutral lipid nanosphere able to exclude water for efficient haem crystallization.
authors.affiliation: Malaria Research Institute, W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Pisciotta
authors.forename: Isabelle
authors.initials: I
authors.lastname: Coppens
authors.forename: Abhai K
authors.initials: AK
authors.lastname: Tripathi
authors.forename: Peter F
authors.initials: PF
authors.lastname: Scholl
authors.forename: Joel
authors.initials: J
authors.lastname: Shuman
authors.forename: Sunil
authors.initials: S
authors.lastname: Bajad
authors.forename: Vladimir
authors.initials: V
authors.lastname: Shulaev
authors.forename: David J
authors.initials: DJ
authors.lastname: Sullivan
mesh_terms: D000818:Animals; D003460:Crystallization; D006420:Hemeproteins / Q000737:chemistry* / Q000378:metabolism; D008055:Lipids / Q000737:chemistry*; D013058:Mass Spectrometry; D043942:Nanotubes / Q000737:chemistry*; D010963:Plasmodium falciparum / Q000737:chemistry / Q000378:metabolism*; D011804:Quinolines / Q000494:pharmacology
chemical_list: D006420:Hemeproteins; D008055:Lipids; D011804:Quinolines; C020753:hemozoin