Dual stage synthesis and crucial role of cytoadherence-linked asexual gene 9 in the surface expression of malaria parasite var proteins.
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family members mediate the adherence of parasite-infected red blood cells (IRBCs) to various host receptors. A previous study has shown that the parasite protein, cytoadherence-linked asexual gene 9 (CLAG9), is also essential for IRBC adherence. However, how CLAG9 influences this process remains unknown. In this study, we show that CLAG9 interacts with VAR2CSA, a PfEMP1 that mediates IRBC adherence to chondroitin 4-sulfate in the placenta. Importantly, our results show that the adherent parasites synthesize CLAG9 at two stages--the early ring and late trophozoite stages. Localization studies revealed that a substantial level of CLAG9 is located mainly at or in close proximity of the IRBC membrane in association with VAR2CSA. Upon treatment of IRBCs with trypsin, a significant amount of CLAG9 (≈150 kDa) was converted into ≈142-kDa polypeptide. Together these data demonstrate that a considerable amount of CLAG9 is embedded in the IRBC membrane such that at least a portion of the polypeptide at either N or C terminus is exposed on the cell surface. In parasites lacking CLAG9, VAR2CSA failed to express on the IRBC surface and was located within the parasite. Based on these findings, we propose that CLAG9 plays a critical role in the trafficking of PfEMP1s onto the IRBC surface. These results have important implications for the development of therapeutics for cerebral, placental, and other cytoadherence-associated malaria illnesses.
Goel
Suchi
S
Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
Valiyaveettil
Manojkumar
M
Achur
Rajeshwara N
RN
Goyal
Atul
A
Mattei
Denise
D
Salanti
Ali
A
Trenholme
Katharine R
KR
Gardiner
Donald L
DL
Gowda
D Channe
DC
D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002809:Chondroitin Sulfates / Q000502:physiology; D016054:DNA, Protozoan / Q000235:genetics; D004910:Erythrocyte Membrane / Q000469:parasitology / Q000502:physiology / Q000648:ultrastructure; D004912:Erythrocytes / Q000469:parasitology; D005260:Female; D055786:Gene Knockout Techniques; D017125:Genes, Protozoan; D006790:Host-Parasite Interactions / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D016253:Microscopy, Immunoelectron; D046912:Multiprotein Complexes; D010920:Placenta / Q000469:parasitology / Q000502:physiology; D010963:Plasmodium falciparum / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity* / Q000502:physiology*; D011247:Pregnancy; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
D000953:Antigens, Protozoan; D015815:Cell Adhesion Molecules; D016054:DNA, Protozoan; D046912:Multiprotein Complexes; D015800:Protozoan Proteins; C512601:VAR2CSA protein, Plasmodium falciparum; C407823:clag9 protein, Plasmodium falciparum; D002809:Chondroitin Sulfates
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