Evidence of NAAG-family tripeptide NAAG2 in the Drosophila nervous system.

N-acetylaspartylglutamate (NAAG) is a common neurotransmitter in the mammalian nervous system; however, it has never been reported in the nervous system of the fruit fly, Drosophila melanogaster. Using antiserum against NAAG, we localized NAAG-like immunoreactivity to neurons in the ventral nerve cord and to type Is glutamatergic nerve terminals in larval neuromuscular junctions. Using liquid chromatography tandem mass spectrometry (LC-MS), we failed to find NAAG but found the related peptide N-acetylaspartylglutamylglutamate (NAAG2 ) in Drosophila CNS and body wall tissue. This is the first report of any NAAG-family peptide in the nervous system of Drosophila and is also the first report of NAAG2 being present in a much higher concentration than NAAG in the nervous system of any species. Thus, the larval fruit fly presents an interesting model for the study of the functional role of NAAG2 of which very little is known-especially in the absence of an abundance of NAAG.