Extracellular glutamine is essential in cell division and flagellar function in bloodstream forms of Trypanosoma brucei

Abstract

Trypanosoma brucei is the etiologic agent of African trypanosomiasis, also known as sleeping sickness. In the mammalian host, T. brucei is present as replicative and non-replicative bloodstream forms (BSF) referred to as long slender and stumpy, respectively. In the insect vector, the developmental forms are procyclic (PCF), epimastigote, and metacyclic trypomastigote. It is well established that BSF use glucose as the main energy source, and PCF can use glucose but, in its absence, uses amino acids, mainly proline. Due to these facts, the metabolism of amino acids has been well studied in PCF, but less attention has been given to it in BSF. In the present work, we unveil the participation of glutamine (Gln), the most abundant amino acid in the human blood, in BSF proliferation. According to the data presented herein, in the absence of extracellular Gln, cell cycle progress, as well as kinetoplast and flagella distribution and function among daughter cells, are widely compromised, yielding polyploid multiflagellated cells with reduced motility. In addition, the Gln-poor medium resulted in cells with a massive alteration in the proteome glutamylation. These alterations were reverted when Gln was added to the culture media. An analysis of the glutamylproteome of cells incubated in Gln-poor medium, followed by a Gene Ontology (GO) analysis, suggested a relationship between glutamylation and biological processes such as gene expression and regulation, cell cycle, and bioenergetics metabolism, in addition to cytoskeleton dynamics in BSF of T. brucei.