Wednesday, December 31, 2014

Reassessment of the role of aromatic amino acid hydroxylases and the effect of infection by Toxoplasma gondii on host dopamine levels

 2014 Dec 29. pii: IAI.02465-14. [Epub ahead of print]


Toxoplasma gondii infection has previously been described to cause infected mice to lose their fear of cat urine. This behavioral manipulation has been proposed to involve alterations of host dopamine pathways due to parasite-encoded aromatic amino acid hydroxylases. Here, we report successful knockout and complementation of the aromatic amino acid hydroxylase AAH2 gene, with no observable phenotype in parasite growth or differentiation in vitro and in vivo. Additionally, expression levels of the two aromatic amino acid hydroxylases were negligible both in tachyzoites and in bradyzoites. Finally, we were unable to confirm previously described effects of parasite infection on host dopamine either in vitro or in vivo, even when AAH2 was over-expressed using the BAG1 promoter. Together, these data indicate that AAH enzymes in the parasite do not cause global or regional alterations of dopamine in the host brain, although they may locally affect this pathway. Additionally, our findings suggest alternative roles for the AHH enzymes in T. gondii since AAH1 is essential for growth in non-dopaminergic cells.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
[PubMed - as supplied by publisher]

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