The malaria parasite cyclic GMP-dependent protein kinase plays a central role in blood-stage schizogony.
A role for the Plasmodium falciparum cyclic GMP (cGMP)-dependent protein kinase (PfPKG) in gametogenesis in the malaria parasite was elucidated previously. In the present study we examined the role of PfPKG in the asexual blood-stage of the parasite life cycle, the stage that causes malaria pathology. A specific PKG inhibitor (compound 1, a trisubstituted pyrrole) prevented the progression of P. falciparum schizonts through to ring stages in erythrocyte invasion assays. Addition of compound 1 to ring-stage parasites allowed normal development up to 30 h postinvasion, and segmented schizonts were able to form. However, synchronized schizonts treated with compound 1 for > or =6 h became large and dysmorphic and were unable to rupture or liberate merozoites. To conclusively demonstrate that the effect of compound 1 on schizogony was due to its selective action on PfPKG, we utilized genetically manipulated P. falciparum parasites expressing a compound 1-insensitive PfPKG. The mutant parasites were able to complete schizogony in the presence of compound 1 but not in the presence of the broad-spectrum protein kinase inhibitor staurosporine. This shows that PfPKG is the primary target of compound 1 during schizogony and provides direct evidence of a role for PfPKG in this process. Discovery of essential roles for the P. falciparum PKG in both asexual and sexual development demonstrates that cGMP signaling is a key regulator of both of these crucial life cycle phases and defines this molecule as an exciting potential drug target for both therapeutic and transmission blocking action against malaria.
Taylor
Helen M
HM
Wellcome Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom.
McRobert
Louisa
L
Grainger
Munira
M
Sicard
Audrey
A
Dluzewski
Anton R
AR
Hopp
Christine S
CS
Holder
Anthony A
AA
Baker
David A
DA
D000818:Animals; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D006801:Humans; D008018:Life Cycle Stages / Q000502:physiology; D008288:Malaria / Q000469:parasitology*; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000472:pathogenicity / Q000502:physiology*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*
D004791:Enzyme Inhibitors; D015800:Protozoan Proteins; D017869:Cyclic GMP-Dependent Protein Kinases