PT  - JOURNAL ARTICLE
AU  - David W. Cobb
AU  - Anat Florentin
AU  - Michelle Krakowiak
AU  - Vasant Muralidharan
TI  - The exported chaperone PfHsp70x is dispensable for the <em>Plasmodium falciparum</em> intraerythrocytic lifecycle
AID  - 10.1101/113365
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 113365
4099  - http://biorxiv.org/content/early/2017/03/03/113365.1.short
4100  - http://biorxiv.org/content/early/2017/03/03/113365.1.full
AB  - Export of parasite proteins into the host erythrocyte is essential for survival of Plasmodium falciparum during its asexual lifecycle. While several studies described key factors within the parasite that are involved in protein export, the mechanisms employed to traffic exported proteins within the host cell are currently unknown. Members of the Hsp70 family of chaperones, together with their Hsp40 co-chaperones, facilitate protein trafficking in other organisms, and are thus likely used by P. falciparum in the trafficking of its exported proteins. A large group of Hsp40 proteins is encoded by the parasite and exported to the host cell, but only one Hsp70, PfHsp70x, is exported with them. PfHsp70x is absent from most Plasmodium species and is found only in P. falciparum and closely-related species that infect Apes. Herein, we have utilized CRISPR/Cas9 genome editing in P. falciparum to investigate the essentiality of PfHsp70x. We show that parasitic growth was unaffected by knockdown of PfHsp70x using both the DHFR-based Destabilization Domain and the glmS ribozyme system. Similarly, a complete gene knockout of PfHsp70x did not affect the ability of P. falciparum to proceed through its intraerythrocytic lifecycle. The effect of PfHsp70x knockout on the export of proteins to the host RBC was tested and we found that this process was unaffected. These data show that although PfHsp70x is the sole exported Hsp70, it is not essential for the asexual development of P. falciparum.