title: SSP3 is a novel Plasmodium yoelii sporozoite surface protein with a role in gliding motility.
abstract: Plasmodium sporozoites develop within oocysts in the mosquito midgut wall and then migrate to the salivary glands. After transmission, they embark on a complex journey to the mammalian liver, where they infect hepatocytes. Proteins on the sporozoite surface likely mediate multiple steps of this journey, yet only a few sporozoite surface proteins have been described. Here, we characterize a novel, conserved sporozoite surface protein (SSP3) in the rodent malaria parasite Plasmodium yoelii. SSP3 is a putative type I transmembrane protein unique to Plasmodium. By using epitope tagging and SSP3-specific antibodies in conjunction with immunofluorescence microscopy, we showed that SSP3 is expressed in mosquito midgut oocyst sporozoites, exhibiting an intracellular localization. In sporozoites derived from the mosquito salivary glands, however, SSP3 localized predominantly to the sporozoite surface as determined by immunoelectron microscopy. However, the ectodomain of SSP3 appeared to be inaccessible to antibodies in nonpermeabilized salivary gland sporozoites. Antibody-induced shedding of the major surface protein circumsporozoite protein (CSP) exposed the SSP3 ectodomain to antibodies in some sporozoites. Targeted deletion of SSP3 adversely affected in vitro sporozoite gliding motility, which, surprisingly, impacted neither their cell traversal capacity, host cell invasion in vitro, nor infectivity in vivo. Together, these data reveal a previously unappreciated complexity of the Plasmodium sporozoite surface proteome and the roles of surface proteins in distinct biological activities of sporozoites.
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA Institute of Biology, Freie Universitaet Berlin, Berlin, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Harupa
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA.
authors.forename: Brandon K
authors.initials: BK
authors.lastname: Sack
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA.
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Lakshmanan
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA.
authors.forename: Nadia
authors.initials: N
authors.lastname: Arang
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA.
authors.forename: Alyse N
authors.initials: AN
authors.lastname: Douglass
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA.
authors.forename: Brian G
authors.initials: BG
authors.lastname: Oliver
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA.
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Stuart
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA.
authors.forename: D Noah
authors.initials: DN
authors.lastname: Sather
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Lindner
authors.affiliation: Department of Medicine, University of Washington, Seattle, Washington, USA.
authors.forename: Kevin
authors.identifier: http://orcid.org/0000-0002-2967-3079
authors.initials: K
authors.lastname: Hybiske
authors.affiliation: Department of Molecular Parasitology, Ehime University, Toon, Ehime, Japan.
authors.forename: Motomi
authors.initials: M
authors.lastname: Torii
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, USA Department of Global Health, University of Washington, Seattle, Washington, USA stefan.kappe@seattlebiomed.org.
authors.forename: Stefan H I
authors.initials: SH
authors.lastname: Kappe
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan; D000939:Epitopes; D005260:Female; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D009068:Movement; D010967:Plasmodium yoelii / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D034101:Sporozoites / Q000378:metabolism*
chemical_list: D000913:Antibodies, Protozoan; D000939:Epitopes; D008565:Membrane Proteins; D015800:Protozoan Proteins