Post-translational modification of proteins by tyrosine phosphorylation is a critical feature in the evolution of multicellular metazoans. Recognition of phosphotyrosine-containing sequences is accomplished primarily by SH2 domains. These modular protein domains emerged in the simplest animals and have co-evolved with tyrosine kinases into complex and essential signaling systems. This project seeks to establish an integrated program of research and education into protein-protein interactions in signal transduction using approaches at the interface of the physical and biological sciences. Bioinformatic approaches, cell biology, peptide chemistry and genetics will be integrated to examine SH2 domains from a systems level, an evolutionary perspective and in terms of their role in promoting self-assembling molecular machines for signal transduction.
Intellectual goals for the project are:
1. Following on Dr. Nash's bioinformatic analysis of the human complement of SH2 domains, his research group will analyze the genomes of 14 species that cover the full range of SH2 domain evolution from the first appearance of functional phosphotyrosine signaling in social amoeba, through to humans. The development of novel SH2 protein architectures along with duplication and divergence will be traced to evolutionary events and changes in organismal complexity in terms of body plans and the development of new systems such as the adaptive immune system. His SH2 database and website (http://sh2.uchicago.edu/) will be extended to contain updated information regarding SH2 domain structures, targeted gene disruptions, alignments, tree structures, and evolutionary.
2. To define the specificity of a wide range of SH2 domains for physiological peptide ligands, an array of 192 peptides has been developed that comprehensively defines early events in Fibroblast growth factor, Insulin and Insulin-like growth factor signaling. By probing such arrays with some 50 SH2 domains that represent the various classes of SH2 domains, one can both identify potential interactions as well as use the ensemble data to define the specificity of SH2 domains for physiological ligands. The role of non-permissive residues and context-specific interactions in governing selectivity for physiological ligands will be investigated.
Intellectual merit Successful completion of this project will provide understanding of the evolution of phosphotyrosine signaling in metazoans, how physiological interaction specificity has evolved to detail complex signaling networks and how the SH2 interaction-space has evolved to generate diversity in cellular signaling. The proposed work will extend our understanding of both individual SH2 domain-containing proteins as well as how phosphotyrosine based signaling functions have evolved to promote assembly of the molecular machines of signal transduction.
Broader Impact This work will have broad implications in terms of the understanding of phosphotyrosine signal transduction as well as understanding of specificity and diversity among protein interaction domains. As interaction domains are increasingly implicated in generating combinatorial complexity required in the evolution of higher organisms, it is increasingly necessary to fully develop paradigms of this sort. Educationally, this project will expose a number of young scientists to experimental and symbolic approaches at the interface of biology, chemistry and computational/bioinformatic sciences. It will assist in training a future generation of scientists equipped to tackle complex, multi-factorial problems utilizing systems approaches
