Cells receive and respond to local signals to communicate with their environment, and errors in these cell signaling pathways can lead to a number of different human diseases. A significant challenge in describing this and other cellular pathways is that many interactions among signaling proteins rely on just a small number of contacts between their amino acid building blocks, leading to promiscuity and overlap in binding partners. With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Jeanine Amacher from Western Washington University to investigate how cell signaling proteins can specifically recognize one another with the number of contacts limited to 10 or less amino acids between them. This project characterizes every interacting amino acid involved in protein recognition for one set of proteins along the cell signaling pathway and elucidates how these interactions evolved. In addition, the project provides undergraduate and masters level graduate students with firsthand experience in structural biology and protein biochemistry to prepare them for STEM-related careers.
An important class of protein-protein interactions in the cell involve recognition of short linear motifs (SLiMs) or peptides. These interactions are critical in signaling and trafficking components in the cell, but are often relatively weak in affinity and transient. Examples include kinase, phosphatase, SH2, and PDZ domain-mediated interactions. However, the recognition of only a couple of amino acid positions by SLiM-binding domains results in interaction networks that greatly overlap, rendering the dissection biologically-important interactions nearly impossible based on the analysis of motifs alone. In this project, the PDZ domain is used as a model system to define the role of non-motif selectivity determinants in SLiM- or peptide mediated interactions. PDZ domains recognize the extreme C-terminus of target proteins through binding motifs that are based on only two residues. Likewise, two sequences can bind dramatically different numbers of PDZ domains. For example, the C-terminal sequence of the human papillomavirus E6 oncoprotein (HPV16 E6) interacts with over a dozen PDZ domain containing proteins, while the C terminal sequence of cystic fibrosis transmembrane conductance regulator (CFTR) interacts with less than five. Both HPV16 E6 and CFTR contain identical motif residues. The overall objectives in this project are to (i) dissect the promiscuity of these two target sequences at non-motif, or modulator, residues and (ii) define the role of modulator residues throughout evolution. The central hypothesis of this proposal is that modulator preferences dictate cellular interaction networks. The principles emerging from this project are applicable to other SLiM-binding domain families.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
