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

Genome-Wide Identification and Functional Characterization of the Acyl-CoA Dehydrogenase (ACAD) Family in Fusarium sacchari

Fusarium sacchari is one of the primary causal agents of Pokkah boeng disease (PBD), an important disease of sugarcane worldwide. The acyl-CoA dehydrogenases (ACADs) constitute a family of flavoenzymes involved in the β-oxidation of fatty acids and amino acid catabolism in mitochondria. However, the role of ACADs in the pathogenesis of F. sacchari is unclear. Here, 14 ACAD-encoding genes (FsACAD-1-FsACAD-14) were identified by screening the entire genome sequence of F. sacchari. The FsACAD genes are distributed across seven chromosomes and were classified into seven clades based on phylogenetic analysis of the protein sequences. In vivo mRNA quantification revealed that the FsACAD genes are differentially expressed during sugarcane infection, and their expression patterns differ significantly in response to the in vitro induction of fatty acids of different classes. Fatty acid utilization assays of the FsACAD-deletion mutants revealed that the FsACADs varied in their preference and ability to break down different fatty acids and amino acids. There was variation in the adverse impact of FsACAD-deletion mutants on fungal traits, including growth, conidiation, stress tolerance, and virulence. These findings provide insights into the roles of FsACADs in F. sacchari, and the identification of FsACADs offers potential new targets for the improved control of PBD.

Branched-chain amino acids modulate the proteomic profile of Trypanosoma cruzi metacyclogenesis induced by proline

Trypanosoma cruzi, the causative agent of Chagas disease, has a complex life cycle that involves triatomine insects as vectors and mammals as hosts. The differentiation of epimastigote forms into metacyclic trypomastigotes within the insect vector is crucial for the parasite's life cycle progression. Factors influencing this process, including temperature, pH, and nutritional stress, along with specific metabolite availability, play a pivotal role. Amino acids like proline, histidine, and glutamine support cell differentiation, while branched-chain amino acids (BCAAs) inhibit it. Interestingly, combining the pro-metacyclogenic amino acid proline with one of the anti-metacyclogenic BCAAs results in viable metacyclics with significantly reduced infectivity. To explore the characteristics of metacyclic parasites differentiated in the presence of BCAAs, proteomics analyses were conducted. Metacyclics obtained in triatomine artificial urine (TAU) supplemented with proline alone and in combination with leucine, isoleucine, or valine were compared. The analyses revealed differential regulation of 40 proteins in TAU-Pro-Leu, 131 in TAU-Pro-Ile, and 179 in TAU-Pro-Val, as compared to metacyclics from TAU-Pro. Among these, 22%, 11%, and 13% of the proteins were associated with metabolic processes, respectively. Notably, enzymes related to glycolysis and the tricarboxylic acid (TCA) cycle were reduced in metacyclics with Pro-BCAAs, while enzymes involved in amino acid and purine metabolic pathways were increased. Furthermore, metacyclics with Pro-Ile and Pro-Val exhibited elevated enzymes linked to lipid and redox metabolism. The results revealed five proteins that were increased and four that were decreased in common in the presence of Pro+BCAAs, indicating their possible participation in key processes related to metacyclogenesis. These findings suggest that the presence of BCAAs can reshape the metabolism of metacyclics, contributing to the observed reduction in infectivity in these parasites.

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.