Characterization of a mitogen‐activated protein (MAP) kinase from Plasmodium falciparum

Abstract

SummaryA mitogen-activated protein (MAP) kinase gene, PfMAP, from Plasmodium falciparum was recently identified. We expressed this gene in Escherichia coli to test whether it encodes a functional MAP kinase. Recombinant PfMAP kinase autophosphorylates on both the tyrosine and threonine residues within the TXY motif, and readily phosphorylates myelin basic protein as exogenous substrate. This identifies the PfMAP gene product as a true member of the growing family of MAP kinases. Wild-type PfMAP kinase expressed in COS-7 (SV40 transformed African green monkey kidney) cells seemed to induce apoptosis in these cells. Western blots and immunoprecipitations indicated that the kinase is expressed during the growth of the parasite in the red blood cell as three major forms: truncated forms with apparent molecular masses of 40 kDa and 80 kDa, and as a protein of Ϸ150 kDa. The 40 kDa form is present throughout the intraerythrocytic development, whereas the two larger forms are only detected in mature parasites. The 40 kDa and 80 kDa forms are tyrosine phosphorylated, indicating that they represent the active forms of the PfMAP kinase. The total PfMAP kinase activity constantly increases with the maturation of the parasite.

Disruption of the PfPK7Gene Impairs Schizogony and Sporogony in the Human Malaria ParasitePlasmodium falciparum

“…Despite the presence of two MAPK-encoding genes, Pfmap-1 (6,12,15) and Pfmap-2 (7), the P. falciparum genome does not possess orthologues of the MAPK kinase (also called MEK, for MAP/ERK kinase) family (1,28), raising the question of the mode of activation of Pfmap-1 and Pfmap-2. PfPK7 (PlasmoDB database identifier PFB0605w) is the P. falciparum enzyme with the highest level of homology to MEKs (8).…”

The Role of Tyrosine Phosphorylation in Regulation of Signal Transduction Pathways in Unicellular Eukaryotes

“…Use of immunoblot analysis and immunopreciptation reaction has allowed revealing in P. falciparum four different MAP kinase forms: p40, p80, p100, and p150 (Lin et al, 1996, Graeser et al, 1997. The total MAP kinase activities increased in the process of parasite maturation (Graeser et al, 1997). Activity of the p80 kinase was high at the asexual stage of parasite development, whereas the p100 protein activity, on the contrary, in gametes and zygote.…”

“…A MAPK homologue of Plasmodium falciparum, PfMAP (also known as Pfmap-1), was simultaneously discovered independently in three laboratories (Doerig et al, 1996;Lin et al, 1996;Graeser et al, 1997). It was shown that, like other MAP kinases, it contained a TXYmotif in the kinase subdomain VIII, whose phosphorylation at tyrosine and threonine is essential for activity (Robbins et al, 1993;Graeser et al, 1997).…”

“…It was shown that, like other MAP kinases, it contained a TXYmotif in the kinase subdomain VIII, whose phosphorylation at tyrosine and threonine is essential for activity (Robbins et al, 1993;Graeser et al, 1997). Use of immunoblot analysis and immunopreciptation reaction has allowed revealing in P. falciparum four different MAP kinase forms: p40, p80, p100, and p150 (Lin et al, 1996, Graeser et al, 1997.…”

“…Recently, MAP kinases and genes encoding microbial MAPK in parasitic fungi Fusarum oxysporum (Di Pietro et al, 2001), in protozoan organisms Plasmodium falciparum (Doerig et al, 1996;Lin et al, 1996;Graeser et al, 1997), Toxoplasma gondii (Ng et al, 1995(Ng et al, , 1997Roisin et al, 2000), Tetrahymena thermophila and Tetrahymena pyriformis (Nakashima et al, 1999), Trypanosoma brucei Wang, 1994, 1997), and Leishmania mexicana (Wiese, 1998) have been identified. These kinases contribute to amplification and specificity of transmitted signals in the nucleus to initiate cellular processes, such as growth, development, and morphogenesis.…”