Dynamic Protein-Protein Interactions in Autism and Fragile X Syndrome

Quantifying changes in protein complexes to identify therapeutic targets and optimize drug candidates

Technology Overview

Dr. Stephen E.P. SmithMore than 100 genes — including the gene that causes fragile X syndrome — are associated with autism spectrum disorders (ASDs). To understand how the products of these genes, alone and in combination, contribute to ASD, the Smith group uses a novel proteomics method: quantitative multiplex immunoprecipitation (QMI). Using QMI to measure hundreds of dynamic interactions of proteins linked to ASD, Dr. Smith and colleagues are identifying genetic pathways and protein complexes that contain ASD therapeutic targets.

QMI can measure the changing associations of proteins in large complexes, such as during neural signal transduction. In QMI, protein complexes are immunoprecipitated from neural cells that can contain mutations associated with ASD or that have been stimulated with neurotransmitters. Proteins in the complexes are quantified using mass spectrometry or labeled antibody probes detected by flow cytometry.

Currently, research on ASDs in the Smith lab focuses on the glutamate synaptic response, which contributes to social behavior and learning. Many ASD-associated genes disrupt this response. Using QMI, Dr. Smith and colleagues determined that, in mice, mutations in ASD-linked genes Homer1 and Shank3B alter interactions with signal transduction complexes in glutamate synapses. Some disrupted interactions involve Fyn, a Src-family kinase that interacts with the glutamate receptor.

The Smith group used QMI to discover that Fyn is hyperactivated in fragile X syndrome. Hyperactive Fyn leads to abnormal responses to neurotransmitters in mice with the fragile X mutation. To date, no drugs are approved to treat fragile X syndrome. Src-family kinases, however, are implicated in cancers and many small-molecule drugs target them.

Dr. Smith and colleagues found that the Src-kinase inhibitor saracatinib, which shows safety in Phase II trials and has been tested for neurological disorders, restores social behavior and learning defects in fragile X mice. It also resolves the fragile X molecular defect of protein overexpression.

Dr. Smith is interested in industry partnerships to use QMI to further identify specific drug targets for ASDs and related conditions. He is interested in partnerships to optimize saracatinib or other Src-family inhibitors to treat fragile X syndrome.

Stage of Development

• Pre-clinical in vitro
• Pre-clinical in vivo

Partnering Opportunities

• Collaborative research opportunity
• Drug development opportunity
• Sponsored research agreement
• Consultation agreement

Publications

1. Heavner WE, Lautz JD, Speed HE…Smith SEP. Remodeling of the Homer-Shank interactome mediates homeostatic plasticity. Sci Signal. 2021;14(681):eabd7325.
2. Heavner WE, Smith SEP. Resolving the synaptic versus developmental dichotomy of autism risk genes. Trends Neurosci. 2020;43(4):227-241.
3. Brown EA, Neier SC, Neuhauser C…Smith SEP. Quantification of protein interaction network dynamics using multiplexed co-immunoprecipitation. J Vis Exp. 2019;(150):10.3791/60029.
4. Brown EA, Lautz JD, Davis TR...Smith SEP. Clustering the autisms using glutamate synapse protein interaction networks from cortical and hippocampal tissue of seven mouse models. Mol Autism. 2018;9:48.
5. Lautz JD, Brown EA, Williams VanSchoiack AA, Smith SEP. Synaptic activity induces input-specific rearrangements in a targeted synaptic protein interaction network. J Neurochem. 2018;146(5):540-559.

Learn More

• SEPS Lab website