Ancestry and progeny of nutrient amino acid transporters

• Published in: Proceedings of the National Academy of Sciences - PNAS 2005-02, Vol.102 (5), p.1360-1365
• Main Authors: Boudko, D.Y, Kohn, A.B, Meleshkevitch, E.A, Dasher, M.K, Seron, T.J, Stevens, B.R, Harvey, W.R
• Format: Article
• Language: English
• Subjects: Aedes - growth & development; Aedes aegypti; Amino Acid Sequence; amino acid sequences; Amino acid transport systems; Amino Acid Transport Systems - classification; Amino Acid Transport Systems - genetics; amino acid transporters; Amino acids; Animals; Base Sequence; Biochemistry; Biological Sciences; Cloning, Molecular; complementary DNA; DNA Primers; Electric current; electrophysiology; Essential amino acids; Female; free amino acids; In Situ Hybridization; Insect genetics; Insect larvae; Larva; Membrane Potentials - physiology; Membranes; Midgut; Molecular Sequence Data; neurotransmitter transporters; nucleotide sequences; nutrient amino acid transporters; Oocytes; Oocytes - physiology; Patch-Clamp Techniques; Phenotypes; Phylogeny; physiological transport; Plasma; Polymerase chain reaction; Restriction Mapping; Sequence Alignment; Sequence Homology, Amino Acid; Transcription, Genetic; Xenopus laevis
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0405183101

The biosynthesis of structural and signaling molecules depends on intracellular concentrations of essential amino acids, which are maintained by a specific system of plasma membrane transporters. We identify a unique population of nutrient amino acid transporters (NATs) within the sodium-neurotransmitter symporter family and have characterized a member of the NAT subfamily from the larval midgut of the Yellow Fever vector mosquito, Aedes aegypti (aeAAT1, AAR08269), which primarily supplies phenylalanine, an essential substrate for the synthesis of neuronal and cuticular catecholamines. Further analysis suggests that NATs constitute a comprehensive transport metabolon for the epithelial uptake and redistribution of essential amino acids including precursors of several neurotransmitters. In contrast to the highly conserved subfamily of orthologous neurotransmitter transporters, lineage-specific, paralogous NATs undergo rapid gene multiplication/substitution that enables a high degree of evolutionary plasticity of nutrient amino acid uptake mechanisms and facilitates environmental and nutrient adaptations of organisms. These findings provide a unique model for understanding the molecular mechanisms, physiology, and evolution of amino acid and neurotransmitter transport systems and imply that monoamine and GABA transporters evolved by selection and conservation of earlier neuronal NATs.