Metabolic cooperation of glucose and glutamine is essential for the lytic cycle of obligate intracellular parasite Toxoplasma gondii

J Biol Chem. 2015 Oct 30. pii: jbc.M114.624619. [Epub ahead of print]

 

Nitzsche R¹, Zagoriy V², Lucius R¹, Gupta N³.

 

Toxoplasma gondii is a widespread protozoan parasite, infecting nearly all warm-blooded organisms. Asexual reproduction of the parasite within its host cells is achieved by consecutive lytic cycles, which necessitates biogenesis of significant energy and biomass. Here, we show that glucose and glutamine are the two major physiologically important nutrients used for the synthesis of macromolecules (ATP, nucleic acid, proteins and lipids) in T. gondii, and either of them is sufficient to ensure the parasite survival. The parasite can counteract genetic ablation of its glucose transporter by increasing the flux of glutamine-derived carbon through the TCA cycle and by concurrently activating gluconeogenesis, which guarantee a continued biogenesis of ATP and biomass for host-cell invasion and parasite replication, respectively. In accord, a pharmacological inhibition of glutaminolysis or oxidative phosphorylation arrests the lytic cycle of the glycolysis-deficient mutant, which is primarily a consequence of impaired invasion due to depletion of ATP. Unexpectedly however, intracellular parasites continue to proliferate, albeit slower, notwithstanding a simultaneous deprivation of glucose and glutamine. Growth defect in the glycolysis-impaired mutant is caused by a compromised synthesis of lipids, which cannot be counterbalanced by glutamine, but can be restored by acetate. Consistently, supplementation of parasite cultures with exogenous acetate can amend the lytic cycle of the glucose transport mutant. Such plasticity in the parasite's carbon flux enables a growth-and-survival trade-off in assorted nutrient milieus, which may underlie the promiscuous survival of T. gondii tachyzoites in diverse host cells. Our results also indicate a convergence of parasite metabolism with cancer cells.
Copyright © 2015, The American Society for Biochemistry and Molecular Biology.

KEYWORDS:

bioenergetics; energy metabolism; gluconeogenesis; glucose metabolism; glutamine; glycolysis; lipid synthesis; metabolic regulation; parasite metabolism; tricarboxylic acid cycle (TCA cycle) (Krebs cycle)

PMID:

26518878

[PubMed - as supplied by publisher]