Despite the fact that much is known about the physiological and biochemical consequences of insulin action, the precise mechanism by which insulin transduces its signal, remains unknown. The long term objective of this study is to elucidate the steps involved in the biochemical pathway which begin with the interaction of insulin with its specific receptor and terminate with the multisite phosphorylation of ribosomal protein, S6. This proposal outlines a thorough examination of one of the key enzymes (i.e. S6KI) involved in this pathway by a genetic approach using Drosophila melanogaster as a model system. The specific aim of this proposal is to isolate mutant alleles in the Drosophila S6 kinase gene and to use these alleles to assess the function of this enzyme as well as to identify other factors which may interact in this insulin-mediated pathway. It is hoped that the knowledge gained from this particular genetic approach will enhance our current biochemical understanding of many of the post receptor effects of insulin action.