Amnesiac, a neuropeptide important for regulation of the innate immune response in Drosophila melanogaster. M-L. Wiklund , M.J. Williams , D. Hultmark. Umea Center for Molecular Pathogenesis, Umea University, Umea, Sweden.

   The Drosophila gene amnesiac encodes a 180 amino acid neuropeptide showing weak homology to mammalian pituitary adenylyl cyclase activating peptide (PACAP) and growth hormone releasing hormone (GHRH). Previous studies have put forward that amnesiac functions upstream of the cAMP signalling pathway and is of importance for associative memory formation and regulation of ethanol sensitivity in adult D. melanogaster.The involvement of amnesiac in these two behavioral processes has been suggested to result from different temporal and spatial requirements for the Amnesiac protein. Our study presents yet another facet of amnesiac, showing that the putative neuropeptide may also have an important modulatory function in the regulation of the innate immune response in Drosophila. When amnesiac is ubiquitously and constitutively expressed, the induction of the antimicrobial peptides is inhibited as a response to infections by E. cloacaeand M. luteus.Loss-of-function studies of amnesiac indicate that the neuropeptide participates in an intrinsic regulation of the antimicrobial peptide Cecropin. The identification of a neuropeptide acting as an immune gene is a very interesting subject, since the association between the innate immune response and the central nervous system is a research field in Drosophila,which has previously not been investigated.