Abstract
BackgroundReversible protein phosphorylation is relatively unexplored in the intracellular protozoa of the Apicomplexa family that includes the genus Plasmodium, to which belong the causative agents of malaria. Members of the PP1 family represent the most highly conserved protein phosphatase sequences in phylogeny and play essential regulatory roles in various cellular pathways. Previous evidence suggested a PP1-like activity in Plasmodium falciparum, not yet identified at the molecular level.ResultsWe have identified a PP1 catalytic subunit from P. falciparum and named it PfPP1. The predicted primary structure of the 304-amino acid long protein was highly similar to PP1 sequences of other species, and showed conservation of all the signature motifs. The purified recombinant protein exhibited potent phosphatase activity in vitro. Its sensitivity to specific phosphatase inhibitors was characteristic of the PP1 class. The authenticity of the PfPP1 cDNA was further confirmed by mutational analysis of strategic amino acid residues important in catalysis. The protein was expressed in all erythrocytic stages of the parasite. Abrogation of PP1 expression by synthetic short interfering RNA (siRNA) led to inhibition of parasite DNA synthesis.ConclusionsThe high sequence similarity of PfPP1 with other PP1 members suggests conservation of function. Phenotypic gene knockdown studies using siRNA confirmed its essential role in the parasite. Detailed studies of PfPP1 and its regulation may unravel the role of reversible protein phosphorylation in the signalling pathways of the parasite, including glucose metabolism and parasitic cell division. The use of siRNA could be an important tool in the functional analysis of Apicomplexan genes.
Highlights
Reversible protein phosphorylation is relatively unexplored in the intracellular protozoa of the Apicomplexa family that includes the genus Plasmodium, to which belong the causative agents of malaria
Reversible protein phosphorylation is gaining recognition as a potentially important mechanism of post-translational regulation in protozoan parasites, especially those belonging to the Apicomplexan family
The dephosphorylation of phosphoproteins is universally catalyzed by protein phosphatases that are classified into two major functional groups, protein tyrosine phosphatase (PTP) and protein serine/threonine phosphatase (PP) enzymes with various degrees of dual-specificity are encountered [1,2,3,4,5]
Summary
Reversible protein phosphorylation is relatively unexplored in the intracellular protozoa of the Apicomplexa family that includes the genus Plasmodium, to which belong the causative agents of malaria. Members of the PP1 family represent the most highly conserved protein phosphatase sequences in phylogeny and play essential regulatory roles in various cellular pathways. Reversible protein phosphorylation is gaining recognition as a potentially important mechanism of post-translational regulation in protozoan parasites, especially those belonging to the Apicomplexan family. The majority of Ser/Thr phosphatases belong to three classical groups, namely PP1, PP2A, and PP2B (calcineurin), and possess similar primary structures in their catalytic cores [2,3,6]. PP1 regulates such diverse cellular processes as cell cycle progression, protein synthesis, carbohydrate metabolism, transcription, and neuronal signaling [3,7], underscoring its profound importance in biology. Tautomycin affects PP1 and PP2A nearly but fails to inhibit other phosphatases [8]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
