title: Evidence for a Golgi-to-endosome protein sorting pathway in Plasmodium falciparum.
abstract: During the asexual intraerythrocytic stage, the malaria parasite Plasmodium falciparum must traffic newly-synthesized proteins to a broad array of destinations within and beyond the parasite's plasma membrane. In this study, we have localized two well-conserved protein components of eukaryotic endosomes, the retromer complex and the small GTPase Rab7, to define a previously-undescribed endosomal compartment in P. falciparum. Retromer and Rab7 co-localized to a small number of punctate structures within parasites. These structures, which we refer to as endosomes, lie in close proximity to the Golgi apparatus and, like the Golgi apparatus, are inherited by daughter merozoites. However, the endosome is clearly distinct from the Golgi apparatus as neither retromer nor Rab7 redistributed to the endoplasmic reticulum upon brefeldin A treatment. Nascent rhoptries (specialized secretory organelles required for invasion) developed adjacent to endosomes, an observation that suggests a role for the endosome in rhoptry biogenesis. A P. falciparum homolog of the sortilin family of protein sorting receptors (PfSortilin) was localized to the Golgi apparatus. Together, these results elaborate a putative Golgi-to-endosome protein sorting pathway in asexual blood stage parasites and suggest that one role of retromer is to mediate the retrograde transport of PfSortilin from the endosome to the Golgi apparatus.
authors.affiliation: Department of Biochemistry, Virginia Tech, Blacksburg, Virginia, United States of America.
authors.forename: Priscilla
authors.initials: P
authors.lastname: Krai
authors.affiliation: Department of Biochemistry, Virginia Tech, Blacksburg, Virginia, United States of America.
authors.forename: Seema
authors.initials: S
authors.lastname: Dalal
authors.affiliation: Department of Biochemistry, Virginia Tech, Blacksburg, Virginia, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Klemba
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000595:Amino Acid Sequence; D015139:Blotting, Southern; D020126:Brefeldin A; D011992:Endosomes / Q000378:metabolism / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D006056:Golgi Apparatus / Q000378:metabolism / Q000502:physiology*; D015151:Immunoblotting; D008969:Molecular Sequence Data; D015388:Organelles / Q000502:physiology; D010963:Plasmodium falciparum / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology*; D016415:Sequence Alignment; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins; D000099183:Sortilin
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D020126:Brefeldin A; D020691:rab GTP-Binding Proteins; D000090802:rab7 GTP-Binding Proteins; D000099183:Sortilin