The overall goal of this project is to understand how a novel adaptor protein and Src substrate, Fish, contributes to tumorigenic transformation. Src was the first oncogene to be discovered and the first tyrosine kinase. Src is a very potent oncogene. It transforms cells by stimulating cell division, by eliciting the production of autocrine growth factors, by preventing apoptosis, and by increasing cell motility and invasiveness. Each of these pathways is important to understand, since they are also features of human tumors. Indeed, Src activity has been shown to be elevated in human tumors, particularly those of breast and colon, and its increased activity has been correlated with a more aggressive phenotype. Although we know much of how Src switches on signal transduction pathways, we cannot yet fully describe how it participates in pathways controlling growth factor production, movement and invasion. This is likely because of an incomplete description of Src substrates. We have isolated a novel substrate of Src called Fish. Fish is a scaffold or adaptor protein. That is, it lacks catalytic activity, but contains multiple motifs that allow it to associate with other proteins as well as with lipids. Fish has one PX domain, five SH3 domains, as well as multiple motifs that could mediate association with SH2- and SH3-domain containing proteins. We have recently found that Fish associates with the cytoplasmic tails of members of the ADAMs family. These are proteins with metalloprotease, adhesion and fusion domains that are involved in shedding of active growth factors from cells, cell-cell interactions, and fusion of specialized cells such as myoblasts. Some members of the ADAMs family are over-expressed in human cancers. Our long-term objective is to understand how phosphorylation of Fish by Src and association of Fish with ADAMs family proteins (and other signaling molecules) contributes to normal and tumor cell physiology. We propose to characterize the interaction of Fish with the ADAMs in more detail as well as isolate more Fish-interacting proteins. We will also define Fish function in development by creating and analyzing Fish knockout mice. And finally, we will test the hypothesis that the Fish-ADAM association mediates the production of autocrine growth factors, and/or motility observed in both Src-transformed cells and human tumor cells. These studies will contribute to our understanding of the mechanisms of oncogenesis.
