Plasmodium Rab5b is secreted to the cytoplasmic face of the tubovesicular network in infected red blood cells together with N-acylated adenylate kinase 2Report as inadecuate

Plasmodium Rab5b is secreted to the cytoplasmic face of the tubovesicular network in infected red blood cells together with N-acylated adenylate kinase 2 - Download this document for free, or read online. Document in PDF available to download.

Malaria Journal

, 15:323

First Online: 17 June 2016Received: 02 April 2016Accepted: 08 June 2016DOI: 10.1186-s12936-016-1377-4

Cite this article as: Ebine, K., Hirai, M., Sakaguchi, M. et al. Malar J 2016 15: 323. doi:10.1186-s12936-016-1377-4


BackgroundRab5 GTPase regulates membrane trafficking between the plasma membrane and endosomes and harbours a conserved C-terminal isoprenyl modification that is necessary for membrane recruitment. Plasmodium falciparum encodes three Rab5 isotypes, and one of these, Rab5b PfRab5b, lacks the C-terminal modification but possesses the N-terminal myristoylation motif. PfRab5b was reported to localize to the parasite periphery. However, the trafficking pathway regulated by PfRab5b is unknown.

MethodsA complementation analysis of Rab5 isotypes was performed in Plasmodium berghei. A constitutively active PfRab5b mutant was expressed under the regulation of a ligand-dependent destabilization domain DD-tag system in P. falciparum. The localization of PfRab5b was evaluated after removing the ligand followed by selective permeabilization of the membrane with different detergents. Furthermore, P. falciparum N-terminally myristoylated adenylate kinase 2 PfAK2 was co-expressed with PfRab5b, and trafficking of PfAK2 to the parasitophorous vacuole membrane was examined by confocal microscopy.

ResultsPfRab5b complemented the function of PbRab5b, however, the conventional C-terminally isoprenylated Rab5, PbRab5a or PbRab5c, did not. The constitutively active PfRab5b mutant localized to the cytosol of the parasite and the tubovesicular network TVN, a region that extends from the parasitophorous vacuole membrane PVM in infected red blood cells iRBCs. By removing the DD-ligand, parasite cytosolic PfRab5b signal disappeared and a punctate structure adjacent to the endoplasmic reticulum ER and parasite periphery accumulated. The peripheral PfRab5b was sensitive to extracellular proteolysis after treatment with streptolysin O, which selectively permeabilizes the red blood cell plasma membrane, indicating that PfRab5b localized on the iRBC cytoplasmic face of the TVN. Transport of PfAK2 to the PVM was abrogated by overexpression of PfRab5b, and PfAK2 accumulated in the punctate structure together with PfRab5b.

ConclusionN-myristoylated Plasmodium Rab5b plays a role that is distinct from that of conventional mammalian Rab5 isotypes. PfRab5b localizes to a compartment close to the ER, translocated to the lumen of the organelle, and co-localizes with PfAK2. PfRab5b and PfAK2 are then transported to the TVN, and PfRab5b localizes on the iRBC cytoplasmic face of TVN. These data demonstrate that PfRab5b is transported from the parasite cytosol to TVN together with N-myristoylated PfAK2 via an uncharacterized membrane-trafficking pathway.

KeywordsMembrane trafficking Rab5b GTPase Myristoylation Palmitoylation Adenylate kinase Parasitophorous vacuole membrane Tubovesicular network AbbreviationsPEXELPlasmodium export element

PVMparasitophorous vacuole membrane

PTEXPlasmodium translocon of exported proteins

PVMparasitophorous vacuole membrane

TVNtubovesicular network

PfAK2Plasmodium falciparum adenylate kinase 2


DDdestabilization domain

mAGMonomeric Azami Green

ORFsopen reading frames

PbDTPlasmodium berghei dihydrofolate reductase


SLOstreptolysin O

CRTPlasmodium falciparum chloroquine resistance transporter

DHFRdihydrofolate reductase


PBSphosphate-buffered saline

PMSFphenylmethylsulfonyl fluoride

BSDblasticidin S

Electronic supplementary materialThe online version of this article doi:10.1186-s12936-016-1377-4 contains supplementary material, which is available to authorized users.

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Author: Kazuo Ebine - Makoto Hirai - Miako Sakaguchi - Kazuhide Yahata - Osamu Kaneko - Yumiko Saito-Nakano


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