Over-expression of lactate dehydrogenase enhances differentiation under alkaline conditions

Exp Parasitol. 2009 Feb 5. [Epub ahead of print]

Toxoplasma gondii : over-expression of lactate dehydrogenase enhances differentiation under alkaline conditions

Liwak U, Ananvoranich S.

Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada.

Toxoplasma gondii, an intracellular parasite, has two distinctive growth stages, namely rapidly growing tachzyoites and slowly growing bradyzoites. Here we report a unique physiological function of the last committed glycolytic enzyme of T. gondii, lactate dehydrogenase (TgLDH), which is present in two isoforms and expressed in a stage-specific manner. TgLDH1 is present in tachyzoites while TgLDH2 is found in bradyzoites. Using clonal transgenic parasites over-expressing either TgLDH1 or TgLDH2, we showed that the enzymatic activity, growth and virulence of tachyzoites were unaffected by the presence of the recombinant protein. Interestingly, under alkaline conditions the presence of the recombinant TgLDH proteins increased the differentiation, as detected by the formation of cyst structures in vitro, while green fluorescent protein did not. The differentiation enhancement of the recombinant TgLDH1 and TgLDH2 strongly suggests that TgLDH1 and TgLDH2 have an important physiological function, in addition to being glycolytic enzymes and differentiation markers.

PMID: 19545518 [PubMed - as supplied by publisher]