Structure-function investigations of protein partnerships governing neuronal signaling

点击翻译按钮获取中文摘要

Chemical and electrical signals are transmitted between neurons through a specialized junction called a synapse. For each side of the synapse to function efficiently, hundreds of receptors, intracellular messages and cytoskeletal proteins need to be brought together in highly regulated, yet dynamic way. This fluid state of communication is achieved by scaffolding and adaptor proteins. I use high resolution structural biology methods to determine how scaffolds and adaptors use protein-protein interactions and post-translational modifications to help neurons make connections and respond to external stimuli at the molecular level.******In this proposal, previously published structures from by my group on the adaptor protein HACS1 and the scaffolding protein CASKIN2 are extended to investigations of unconventional protein partnerships mediated by them.******HACS1 is a modular protein whose architecture helps it form partnerships with signal transduction and cytoskeletal proteins. Aim 1 builds upon a previously determined high resolution structure of the HACS1 Src homology-3 (SH3) domain from my group and the discovery that it interacts with the Paired receptor (PIRB) cytosolic region in a novel way. The interaction is believed to be novel because the complement of amino acids at the binding surface of the SH3 domain are atypical as well as the sequence in PIRB that is recognized. The long-term goal of this research is to provide a structural explanation for how negative signals from PIRB inhibit the maturation of neurons through HACS1. In addition to its SH3 domain, HACS1 also has a sterile alpha motif (SAM) domain that is also well known for its ability to support a wide range of protein-protein interactions. Aim 2 focuses upon discovering new partners for the HACS1 SAM domain. The identification of these partners represents an essential first step towards establishing a complete functional description of HACS1. As I have determined many SAM domain structures throughout my career, I can work with my research group to propel the most interesting partners towards high-resolution structural studies. ******Compared to HACS1, the organization of CASKIN2 is more complex thereby earning it the designation of a molecular scaffold, rather than an adaptor. CASKIN2, and CASKIN1 by similarity, are recognized for their roles in vesicle trafficking and creating proper connections between motor neurons and muscle cells. In Aim 3, I will determine the structural basis of how the SAM domain of CASKIN2 interacts with a known, yet poorly defined region, of the LAR receptor phosphatase. The CASKIN2/LAR partnership was selected because the SAM domain is predicted to interact with LAR in a manner that is distinct from other SAM domain structures that I have solved. The biochemical and structural insights from this aim can be extended to the Liprin class of neuronal scaffolds that also use SAM domains to bind LAR.