Plasmodium falciparum glycogen synthase kinase-3: molecular model, expression, intracellular localisation and selective inhibitors.
Worldwide increasing resistance of Plasmodium falciparum to common anti-malaria agents calls for the urgent identification of new drugs. Glycogen synthase kinase-3 (GSK-3) represents a potential screening target for the identification of such new compounds. We have cloned PfGSK-3, the P. falciparum gene homologue of GSK-3 beta. It encodes a 452-amino-acid, 53-kDa protein with an unusual N-terminal extension but a well-conserved catalytic domain. A PfGSK-3 tridimensional homology model was generated on the basis of the recently crystallised human GSK-3 beta. It illustrates how the regions involved in the active site, in substrate binding (P+4 phosphate binding domain) and in activity regulation are highly conserved. Recombinant PfGSK-3 phosphorylates GS-1, a GSK-3-specific peptide substrate, glycogen synthase, recombinant axin and the microtubule-binding protein tau. Neither native nor recombinant PfGSK-3 binds to axin. Expression and intracellular localisation of PfGSK-3 were investigated in the erythrocytic stages. Although PfGSK-3 mRNA is present in similar amounts at all stages, the PfGSK-3 protein is predominantly expressed at the early trophozoite stage. Once synthesized, PfGSK-3 is rapidly transported to the erythrocyte cytoplasm where it associates with vesicle-like structures. The physiological functions of PfGSK-3 for the parasite remain to be elucidated. A series of GSK-3 beta inhibitors were tested on both PfGSK-3 and mammalian GSK-3beta. Remarkably these enzymes show a partially divergent sensitivity to the compounds, suggesting that PfGSK-3 selective compounds might be identified.
Droucheau
Eliane
E
C.N.R.S., Cell Cycle Group, Station Biologique, B.P. 74, 29682 Roscoff cedex, Bretagne, France.
Primot
Aline
A
Thomas
Virginie
V
Mattei
Denise
D
Knockaert
Marie
M
Richardson
Chris
C
Sallicandro
Pina
P
Alano
Pietro
P
Jafarshad
Ali
A
Baratte
Blandine
B
Kunick
Conrad
C
Parzy
Daniel
D
Pearl
Laurence
L
Doerig
Christian
C
Meijer
Laurent
L
D000595:Amino Acid Sequence; D000818:Animals; D060466:Axin Protein; D001483:Base Sequence; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D004912:Erythrocytes / Q000201:enzymology; D015870:Gene Expression; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D010963:Plasmodium falciparum / Q000201:enzymology*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D060466:Axin Protein; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D012097:Repressor Proteins; D038362:Glycogen Synthase Kinase 3