title: Trans expression of a Plasmodium falciparum histidine-rich protein II (HRPII) reveals sorting of soluble proteins in the periphery of the host erythrocyte and disrupts transport to the malarial food vacuole.
abstract: The heme polymer hemozoin is produced in the food vacuole (fv) of the parasite after hemoglobin proteolysis and is the target of the drug chloroquine. A candidate heme polymerase, the histidine-rich protein II (HRPII), is proposed to be delivered to the fv by ingestion of the infected-red cell cytoplasm. Here we show that 97% of endogenous Plasmodium falciparum (Pf) HRPII (PfHRPII) is secreted as soluble protein in the periphery of the red cell and avoids endocytosis by the parasite, and 3% remains membrane-bound within the parasite. Transfected cells release 90% of a soluble transgene PfHRPIImyc into the red cell periphery and contain 10% membrane bound within the parasite. Yet these cells show a minor reduction in hemozoin production and IC(50) for chloroquine. They also show decreased transport of resident fv enzyme PfPlasmepsin I, the endoplasmic reticulum (ER) marker PfBiP, and parasite-associated HRPII to fvs. Instead, all three proteins accumulate in the ER, although there is no defect in protein export from the parasite. The data suggest that novel mechanisms of sorting (i) soluble antigens like HRPII in the red cell cytoplasm and (ii) fv-bound membrane complexes in the ER regulate parasite digestive processes.
authors.affiliation: Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Akompong
authors.forename: Madhusudan
authors.initials: M
authors.lastname: Kadekoppala
authors.forename: Travis
authors.initials: T
authors.lastname: Harrison
authors.forename: Anna
authors.initials: A
authors.lastname: Oksman
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Goldberg
authors.forename: Hisashi
authors.initials: H
authors.lastname: Fujioka
authors.forename: Benjamin U
authors.initials: BU
authors.lastname: Samuel
authors.forename: David
authors.initials: D
authors.lastname: Sullivan
authors.forename: Kasturi
authors.initials: K
authors.lastname: Haldar
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002384:Catalysis; D002738:Chloroquine / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes; D004912:Erythrocytes / Q000469:parasitology*; D005434:Flow Cytometry; D006420:Hemeproteins / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010957:Plasmids / Q000378:metabolism; D010963:Plasmodium falciparum / Q000378:metabolism*; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry*; D013997:Time Factors; D014162:Transfection; D019076:Transgenes; D000099053:Histidine-Rich Glycoprotein
chemical_list: D000939:Epitopes; D006420:Hemeproteins; D011506:Proteins; D000099053:Histidine-Rich Glycoprotein; C020753:hemozoin; D002738:Chloroquine