Branched chain amino acids catabolism as a source of new drug targets in pathogenic protists

AMP deaminase: A crucial regulator in nitrogen stress and lipid metabolism in Mucor circinelloides

Lipid biosynthesis is a significant metabolic response to nitrogen starvation in oleaginous fungi. The oleaginous fungus Mucor circinelloides copes with nitrogen stress by degrading AMP through AMP deaminase (AMPD). However, the mechanism of AMPD in regulating lipogenesis remains largely unclear. To elucidate the mechanism of AMPD in lipid synthesis in this M. circinelloides, we identified two genes (ampd1 and ampd2) encoding AMPD and constructed an ampd double knockout mutant. The engineered M. circinelloides strain elevated cell growth and lipid accumulation, as well as the content of oleic acid (OA) and gamma-linolenic acid (GLA). In addition to the expected increase in transcription levels of genes associated with lipid and TAG synthesis, we observed suppression of lipid degradation and reduced amino acid biosynthesis. This suggested that the deletion of AMPD genes induces the redirection of carbon towards lipid synthesis pathways. Moreover, the pathways related to nitrogen metabolism, including nitrogen assimilation and purine metabolism (especially energy level), were also affected in order to maintain homeostasis. Further analysis discovered that the transcription factors (TFs) related to lipid accumulation were also regulated. This study provides new insights into lipid biosynthesis in M. circinelloides, indicating that the trigger for lipid accumulation is not entirely AMPD-dependent and suggest that there may be additional mechanisms involved in the initiation of lipogenesis.

The branched chain amino acids (BCAAs) modulate the development of the intra-cellular stages of Trypanosoma cruzi

The life cycle of Trypanosoma cruzi, the etiological agent of Chagas disease, involves different forms of the parasite, which alternates between insect and vertebrate hosts. One critical process in the parasite's life cycle is metacyclogenesis, in which the replicative non-infective forms present in the insect midgut differentiate into non-dividing vertebrate-infective forms. It is known that proline (Pro) is important for this process and that leucine (Leu) and isoleucine (Ile) can act as inhibitors of metacyclogenesis. In this study, we investigated further the role of branched-chain amino acids (BCAAs) as negative modulators of parasite differentiation and infection capability in vitro. We found that BCAAs can down-regulate metacyclogenesis, inhibiting Pro-dependent differentiation. Furthermore, we evaluated the ability of all three BCAAs to influence the differentiation of intracellular stages and found that they could modulate the release of trypomastigotes from infected host cells. These findings suggest that BCAAs may have an important role in the complex life cycle of T. cruzi. Thus, enzymes of their metabolism and other interacting proteins could be potential targets for the development of new therapeutic strategies for Chagas disease.