Characterization and isolation of Sex-peptide binding proteins. E. Domanitskaya, E. Kubli. Dept. of Zoology, University Zurich, Zurich, Switzerland.

   In D. melanogaster egg production and oviposition are induced by copulation. Sex-peptide (SP), a 36 aa peptide produced in the accessory glands of males, is transferred during copulation. SP has been shown to be the major player in the stimulation of egg-laying and rejection behaviour in females (see abstract E. Kubli et al.). In spite of our extensive knowledge about the nature and action of SP, the molecular mechanism of the SP response cascade is still unknown. Several attempts have been made to improve our understanding of this enigmatic pathway. Ding et al. 2003. J. Neurobiol.) have characterized two different receptors in terms of binding specificity for SP (one in the nervous system, the other in the genital tract). Both of them are transmembrane or membrane-associated proteins. As the cAMP level is crucial for eliciting the post-mating responses, the receptor for SP could belong to the G-protein Coupled Receptor-group. Moreover, it has been shown that the receptor is developmentally regulated. Based on these facts we carried out a microarray experiment with RNA isolated from 0 d and 3 d old female heads, respectively, to define a list of genes suitable for the role of putative SP-receptor(s). The most promising candidate out of 426 up-regulated genes is GRHR (Gonadotropin-releasing hormone receptor), described as an AKH receptor in Drosophila (Staubli et al. 2001 PNAS). As the developmental regulation has been shown at the protein level, we always have to consider that many proteins are regulated post-transcriptionally, and that protein levels may not be related to RNA levels. So we also considered genes that didnt show any changes at their expression level. We have identified 1296 genes that demonstrated the same level of expression at these two different time-points. To narrow down this list, we are going to apply a protein approach. Binding proteins will be defined on a native PAGE and analysed by the LC- MS/ MS technique.