A versatile proline/alanine transporter in the unicellular pathogen Leishmania donovani regulates amino acid homoeostasis and osmotic stress responses

Abstract

Unlike all other organisms, parasitic protozoa of the family Trypanosomatidae maintain a large cellular pool of proline that, together with the alanine pool, serve as alternative carbon sources as well as reservoirs of organic osmolytes. These reflect adaptation to their insect vectors whose haemolymphs are exceptionally rich in the two amino acids. In the present study we identify and characterize a new neutral amino acid transporter, LdAAP24, that translocates proline and alanine across the Leishmania donovani plasma membrane. This transporter fulfils multiple functions: it is the sole supplier for the intracellular pool of proline and contributes to the alanine pool; it is essential for cell volume regulation after osmotic stress; and it regulates the transport and homoeostasis of glutamate and arginine, none of which are its substrates. Notably, we provide evidence that proline and alanine exhibit different roles in the parasitic response to hypotonic shock; alanine affects swelling, whereas proline influences the rate of volume recovery. On the basis of our data we suggest that LdAAP24 plays a key role in parasite adaptation to its varying environments in host and vector, a phenomenon essential for successful parasitism.

Multi-analytical platform metabolomic approach to study miltefosine mechanism of action and resistance in Leishmania

“…In this sense, Inbard et al [81] proposed recently an appealing hypothesis consisting of the cross-talk among the different amino acid transporters through their large hydrophilic N-terminal extension, typical in Leishmania, which will be modulated allosterically by these amino acids. A suggestive hypothesis is whether the interaction of this tail with the membrane will explore different membrane architectures in the parasite created by dysfunction of the MT transporter [82].Some trends can be detected for free fatty acids anions (FFAA) in R40 parasites.…”

“…Leishmania senses intracellular pools at least for Arg [71] and Pro [81] with crossed-influence between these metabolites. In this sense, Inbard et al [81] proposed recently an appealing hypothesis consisting of the cross-talk among the different amino acid transporters through their large hydrophilic N-terminal extension, typical in Leishmania, which will be modulated allosterically by these amino acids.…”

The Transcriptome ofLeishmania majorDevelopmental Stages in Their Natural Sand Fly Vector

“…This transporter is specific for “nonessential” amino acids, such as proline and alanine, that are known to serve as carbon sources in Leishmania (4, 30–33). Moreover, the transporter has a role in maintaining the homeostasis of amino acids in the free amino acid pool, in which proline, alanine, and glutamate are the most abundant constituents (32, 34). The significant increase in acquisition of carbon sources throughout the development of promastigotes in the fly is consistent with recent studies showing that the differentiation of L. mexicana to amastigotes is coupled with them entering into a “metabolic stringent state,” in which transport and utilization of glucose and amino acids are strongly suppressed, while metabolism of fatty acids via β-oxidation and production of glutamate via the tricarboxylic acid (TCA) cycle is increased (4).…”

Genomic Appraisal of the Multifactorial Basis for In Vitro Acquisition of Miltefosine Resistance in Leishmania donovani

“…35.0540 (logFC, Ϫ5.82) is annotated in the genome as a proteophosphoglycan (PPG5). PPG has been shown to be the key molecule conferring resistance to midgut digestive enzymes during sandfly infection (53 (56). Metabolomics studies have identified increased amounts of proline in HePC-resistant parasites (47).…”