A Plasmodium phospholipase is involved in disruption of the liver stage parasitophorous vacuole membrane.

Burda PC, Roelli MA, Schaffner M, Khan SM, Janse CJ, Heussler VT
Source: PLoS Pathog
Publication Date: (2015)
Issue: 11(3): e1004760
Research Area:
Cells used in publication:
Hep G2
Species: human
Tissue Origin: liver
Plasmodium berghei
Species: unicellular
Tissue Origin:
Nucleofector® I/II/2b
2 × 106 HepG2 cells were transfected with 4 µg pEGFP-N3 plasmid (Clontech) using an Amaxa nucleofector (Lonza) and subsequently seeded into 4-chamber glass bottom dishes. Lonza Summary: In hepatocytes, parasites are surround by the parasitophorous membrane. The authors have found that a phosopholipase, called Plasmodium berghei Phosolipase, is crucial for allowing the parasite to leave the host cells. Furthermore, the authors show that parasites deficient in this phosolipase are impaired in exiting the host cells.
The coordinated exit of intracellular pathogens from host cells is a process critical to the success and spread of an infection. While phospholipases have been shown to play important roles in bacteria host cell egress and virulence, their role in the release of intracellular eukaryotic parasites is largely unknown. We examined a malaria parasite protein with phospholipase activity and found it to be involved in hepatocyte egress. In hepatocytes, Plasmodium parasites are surrounded by a parasitophorous vacuole membrane (PVM), which must be disrupted before parasites are released into the blood. However, on a molecular basis, little is known about how the PVM is ruptured. We show that Plasmodium berghei phospholipase, PbPL, localizes to the PVM in infected hepatocytes. We provide evidence that parasites lacking PbPL undergo completely normal liver stage development until merozoites are produced but have a defect in egress from host hepatocytes. To investigate this further, we established a live-cell imaging-based assay, which enabled us to study the temporal dynamics of PVM rupture on a quantitative basis. Using this assay we could show that PbPL-deficient parasites exhibit impaired PVM rupture, resulting in delayed parasite egress. A wild-type phenotype could be re-established by gene complementation, demonstrating the specificity of the PbPL deletion phenotype. In conclusion, we have identified for the first time a Plasmodium phospholipase that is important for PVM rupture and in turn for parasite exit from the infected hepatocyte and therefore established a key role of a parasite phospholipase in egress.