Additional remarks phenotype | Mutant/mutation
The mutant expresses a C-terminal triple haemagluttinin (HA) and single Strep-II (Str) epitope tagged version of EXP2
Protein (function)
Plasmodium parasites remodel their vertebrate host cells by translocating hundreds of proteins across an encasing membrane into the host cell cytosol via a putative export machinery termed PTEX (Plasmodium Translocon of EXported protein). HSP101 (PbANKA_094120), PTEX150 (PbANKA_100850), EXP2 (PbANKA_133430), PTEX88 (PbANKA_094130) and TRX2 (PbANKA_135800) have been identified as members of the PTEX complex.
These proteins are also expressed in early gametocytes, mosquito and liver stages. Although amenable to genetic tagging, HSP101, PTEX150, EXP2 and PTEX88 could not be genetically deleted in P. berghei (see RMgm-914, RMgm-915, RMgm-916, RMgm-917) in keeping with the obligatory role this complex is postulated to have in maintaining normal blood-stage growth. In contrast, the putative thioredoxin-like protein TRX2 could be deleted, with knockout parasites displaying reduced grow-rates, both in vivo and in vitro (see RMgm-918).
Phenotype
PbEXP2-HA expression in asexual blood stages, sporozoites and liver stage merozoites. Weak expression in gametocytes.
Additional information
Immunofluorescence analyses of ring forms showed that HSP101-HA, PTEX88 and PTEX150-HA clearly co-localised with EXP2, showing a punctate labeling pattern outside the parasite periphery. These observations are in keeping with EXP2, HSP101 and PTEX150 associating at the PVM The localization of TRX2, however, was less clear and made difficult by the fact that expression of TRX2-HA was weak. In the early ring stages some co-labeling of TRX2-HA with EXP2 was observed but more pronounced internal parasite labeling with the anti-HA antibodies (Fig. 2A). As the parasites matured, the localization of TRX2-HA appeared more towards the parasite periphery rather than PV/PVM and its localization within the parasite also more pronounced. By schizont stages TRX2-HA displayed punctate apical labeling, reminiscent of labeling pattern observed with other PTEX components in P. falciparum and Pb150-HA.
PTEX150-HA, HSP101-HA and PTEX88-HA expression was not observed at the PVM in gametocytes. Moreover, the expression of EXP2 at the PVM and punctate labeling of TRX2-HA within gametocytes was weak.
Immunofluorescence analyses showed that EXP2,HSP101 and PTEX150 were expressed in sporozoites and liver stage merozoites.
Other mutants
HSP101, PTEX150, EXP2 and PTEX88 could not be genetically deleted in P. berghei (see RMgm-914, RMgm-915, RMgm-916, RMgm-917)
TRX2 could be deleted, with knockout parasites displaying reduced grow-rates, both in vivo and in vitro (see RMgm-918). |