Isolation and characterization of a leucokinin-like peptide of Drosophila melanogaster

The leucokinin (LK) family of neuropeptides has been found widely amongst i nvertebrates. A member of this family was purified from adults of the fruit fly Drosophila melanogaster, The peptide sequence for Drosophila leucokini n (DLK) was determined as Asn-Ser-Val-Val-Leu-Gly-Lys-Lys-Gln-Arg-Phe-His-S er-Trp-Gly-amide, making it the longest member of the family characterized to date. Synthetic DLK peptide was shown to act to stimulate fluid secretio n in D. melanogaster Malpighian (renal) tubules by approximately threefold, with an EC50 of approximately 10(-10) mol l(-1), and a secondary effect at approximately 10(-7) mol l(-1). DLK also acted to elevate intracellular [C a2+] in the Malpighian tubules by approximately threefold, with an EC50 of 10(-10) to 10(-9) mol l(-1), Responses were detected in stellate cells and occasionally in principal cells, although at no concentration tested did [C a2+] in the principal cell increase significantly above background. In stel late cells, DLK produced a biphasic rise in intracellular [Ca2+] from resti ng levels of 80-100 nmol l(-1), with a transient peak being followed by a s lower rise that peaked at 200-300 nmol l(-1) after 3s, then decayed over ap proximately 10s. The wide range of concentrations over which DLK acts sugge sts the involvement of more than one receptor. The genomic sequence encodin g the DLK peptide has been identified, and the gene has been named pp, The gene resides at cytological location 70E3-70F4 of chromosome 3L. The locali sation of this first Drosophila LK gene in a genetic model permits a geneti c analysis of the locus.