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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Cell. Infect. Microbiol. | doi: 10.3389/fcimb.2018.00413

The micronemal Plasmodium proteins P36 and P52 act in concert to establish the replication-permissive compartment within infected hepatocytes

Silvia A. Arredondo1,  Kristian E. Swearingen2, Thomas Martinson1,  Ryan Steel1, Dorender A. Dankwa1, Anke Harupa1, Nelly Camargo1, William Betz1, Vladimir Vigdorovich1, Brian G. Oliver1,  Niwat Kangwanrangsan3,  Tomoko Ishino4,  Noah Sather1,  Sebastian A. Mikolajczak1, Ashley M. Vaughan1, Motomi Torii4, Robert L. Moritz2 and  Stefan H. Kappe1*
  • 1Center for Infectious Disease Research, United States
  • 2Institute for Systems Biology, United States
  • 3Faculty of Science, Mahidol University, Thailand
  • 4Ehime University, Japan

Within the liver, Plasmodium sporozoites traverse cells searching for a “suitable” hepatocyte, invading these cells through a process that results in the formation of a parasitophorous vacuole (PV), within which the parasite undergoes intracellular replication as a liver stage. It was previously established that two members of the Plasmodium s48/45 protein family, P36 and P52, are essential for productive invasion of host hepatocytes by sporozoites as their simultaneous deletion results in growth-arrested parasites that lack a PV. Recent studies point towards a pathway of entry possibly involving the interaction of P36 with hepatocyte receptors EphA2, CD81 and SR-B1. However, the relationship between P36 and P52 during sporozoite invasion remains unknown. Here we show that parasites with a single P52 or P36 gene deletion each lack a PV after hepatocyte invasion, thereby pheno-copying the lack of a PV observed for the P52/P36 dual gene deletion parasite line. This indicates that both proteins are equally important in the establishment of a PV and act in the same pathway. We created a Plasmodium yoelii P36mCherry tagged parasite line that allowed us to visualize the subcellular localization of P36 and found that it partially co-localizes with P52 in the sporozoite secretory microneme organelles. Furthermore, through co-immunoprecipitation studies in vivo, we determined that P36 and P52 form a protein complex in sporozoites, indicating a concerted function for both proteins within the PV formation pathway. However, upon sporozoite stimulation, only P36 was released as a secreted protein while P52 was not. Our results support a model in which the putatively glycophosphatidylinositol (GPI)-anchored P52 may serve as a scaffold to facilitate the interaction of secreted P36 with the host cell during sporozoite invasion of hepatocytes.

Keywords: Malaria, Plasmodium, Protein complex, invasion, Sporozoite, 6-cys s48/45, microneme secretion, TRAP

Received: 08 Aug 2018; Accepted: 08 Nov 2018.

Edited by:

Tiago W. Mineo, Federal University of Uberlandia, Brazil

Reviewed by:

Sabrina Absalon, Boston Children's Hospital, Harvard Medical School, United States
Alexandre Bougdour, Institut National de la Santé et de la Recherche Médicale (INSERM), France
Carsten Lüder, Institut für Medizinische Mikrobiologie, Universitätsmedizin Göttingen, Germany  

Copyright: © 2018 Arredondo, Swearingen, Martinson, Steel, Dankwa, Harupa, Camargo, Betz, Vigdorovich, Oliver, Kangwanrangsan, Ishino, Sather, Mikolajczak, Vaughan, Torii, Moritz and Kappe. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: PhD. Stefan H. Kappe, Center for Infectious Disease Research, Seattle, United States, stefan.kappe@cidresearch.org