PfeIK1, a eukaryotic initiation factor 2alpha kinase of the human malaria parasite Plasmodium falciparum, regulates stress-response to amino-acid starvation.
BACKGROUND
Post-transcriptional control of gene expression is suspected to play an important role in malaria parasites. In yeast and metazoans, part of the stress response is mediated through phosphorylation of eukaryotic translation initiation factor 2alpha (eIF2alpha), which results in the selective translation of mRNAs encoding stress-response proteins.


METHODS
The impact of starvation on the phosphorylation state of PfeIF2alpha was examined. Bioinformatic methods were used to identify plasmodial eIF2alpha kinases. The activity of one of these, PfeIK1, was investigated using recombinant protein with non-physiological substrates and recombinant PfeIF2alpha. Reverse genetic techniques were used to disrupt the pfeik1 gene.


RESULTS
The data demonstrate that the Plasmodium falciparum eIF2alpha orthologue is phosphorylated in response to starvation, and provide bioinformatic evidence for the presence of three eIF2alpha kinases in P. falciparum, only one of which (PfPK4) had been described previously. Evidence is provided that one of the novel eIF2alpha kinases, PfeIK1, is able to phosphorylate the P. falciparum eIF2alpha orthologue in vitro. PfeIK1 is not required for asexual or sexual development of the parasite, as shown by the ability of pfeik1- parasites to develop into sporozoites. However, eIF2alpha phosphorylation in response to starvation is abolished in pfeik1- asexual parasites


CONCLUSIONS
This study strongly suggests that a mechanism for versatile regulation of translation by several kinases with a similar catalytic domain but distinct regulatory domains, is conserved in P. falciparum.
INSERM U609, Wellcome Centre for Molecular Parasitology, Biomedical Research Centre University of Glasgow, 120 University Place, Glasgow, G12 8TA, UK. cfennell@staffmail.ed.ac.uk
Clare
C
Fennell
Shalon
S
Babbitt
Ilaria
I
Russo
Jonathan
J
Wilkes
Lisa
L
Ranford-Cartwright
Daniel E
DE
Goldberg
Christian
C
Doerig
D000595:Amino Acid Sequence / Q000235:genetics*; D000596:Amino Acids / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015139:Blotting, Southern; D003001:Cloning, Molecular / Q000379:methods; D019295:Computational Biology; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010963:Plasmodium falciparum / Q000235:genetics* / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013217:Starvation; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
D000596:Amino Acids; D015852:Eukaryotic Initiation Factor-2; D011994:Recombinant Proteins; D011494:Protein Kinases; D019892:eIF-2 Kinase