title: 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.
authors.affiliation: Faculty of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Ehud
authors.initials: E
authors.lastname: Inbar
authors.forename: Doreen
authors.initials: D
authors.lastname: Schlisselberg
authors.forename: Marianne
authors.initials: M
authors.lastname: Suter Grotemeyer
authors.forename: Doris
authors.initials: D
authors.lastname: Rentsch
authors.forename: Dan
authors.initials: D
authors.lastname: Zilberstein
mesh_terms: D000222:Adaptation, Physiological; D000409:Alanine / Q000378:metabolism; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism; D001692:Biological Transport; D015152:Blotting, Northern; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D015870:Gene Expression; D005816:Genetic Complementation Test; D018698:Glutamic Acid / Q000378:metabolism; D006706:Homeostasis; D007893:Leishmania donovani / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D009997:Osmotic Pressure; D011392:Proline / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; D015800:Protozoan Proteins; D018698:Glutamic Acid; C033082:proline transporter; D001120:Arginine; D011392:Proline; D000409:Alanine