Nutrient availability regulates proline/alanine transporters in Trypanosoma brucei

Abstract

Trypanosoma brucei is a species of unicellular parasite that can cause severe diseases in livestock and humans, including African trypanosomiasis and Chagas disease. Adaptation to diverse environments and changes in nutritional conditions is essential for T. brucei to establish an infection when changing hosts or during invasion of different host tissues. One such adaptation is the ability of T. brucei to rapidly switch its energy metabolism from glucose metabolism in the mammalian blood to proline catabolism in the insect stages and vice versa. However, the mechanisms that support the parasite's response to nutrient availability remain unclear. Using RNAseq and qRT-PCR, we investigated the response of T. brucei to amino acid or glucose starvation and found increased mRNA levels of several amino acid transporters, including all genes of the amino acid transporter AAT7-B subgroup. Functional characterization revealed that AAT7-B members are plasma membrane-localized in T. brucei and when expressed in Saccharomyces cerevisiae supported the uptake of proline, alanine, and cysteine, while other amino acids were poorly recognized. All AAT7-B members showed a preference for proline, which is transported with high or low affinity. RNAi-mediated AAT7-B downregulation resulted in a reduction of intracellular proline concentrations and growth arrest under low proline availability in cultured procyclic form parasites. Taken together, these results suggest a role of AAT7-B transporters in the response of T. brucei to proline starvation and proline catabolism.

Developmental changes and metabolic reprogramming during establishment of infection and progression of Trypanosoma brucei brucei through its insect host

“…Closely related genes can be differentially regulated. For example, 3 members of the AAT7-B proline/alanine transporter family [ 17 ] are expressed at different times in the midgut (D3 or D15), one is biphasic (midgut D7 and proventriculus) and others show maximum expression in the proventriculus or in the salivary glands.…”

“…It has been shown that procyclic forms can sense and adapt to nutrient availability in culture [ 16 ]. In addition, trypanosomes deprived of glucose or amino acids react by up-regulating transcripts for amino acid transporters [ 17 ].…”

An Update on African Trypanocide Pharmaceutics and Resistance

“…Currently, chemotherapy is the only available option against trypanosomes as efforts to develop a vaccine have been thwarted by the international community, however, the development of trypanocidal resistance has become a realistic threat especially for persons living in endemic regions (103,145,157,158). Trypanosoma transport proteins [on the surface of the parasite (see Table 4)] are responsible for pathogen survival; and trypanocidal resistance has been associated with changes in the pathogen transportome leading to dysfunction and a loss in therapeutical potential once drugs can no longer be absorbed by the parasite (152)(153)(154)159). This justifies the need to promote further research for the discovery of novel chemotherapeutical options for the control of trypanosomiasis.…”

The Multifaceted Roles of Proline in Cell Behavior

“…Protozoan parasites adapt their metabolism to the mutable environments encountered throughout their life cycle, including the hemolymph of their insect vectors (Bringaud et al, 2012). Trypanosoma brucei, the causative agent of sleeping sickness, is transmitted by tsetse flies (Glossina diptera), and both organisms can oxidize L-Pro to accomplish ATP biosynthesis (Figure 3; Michalkova et al, 2014;Mantilla et al, 2017;Smith et al, 2017;Dolezelova et al, 2020;Haindrich et al, 2021;Villafraz et al, 2021). L-Pro sustains Trypanosoma cruzi (the causative agent of Chagas disease) cell invasion and intracellular epimastigote-to-trypomastigote transition (Figure 3; Martins et al, 2009;Mantilla et al, 2015;Barison et al, 2017).…”