As the major defining characteristic of Alzheimer's disease (AD) brains is the excessive accumulation of toxic proteins called A? and Tau, understanding the biological mechanisms by which A? connects to tau dysfunction are critical for designing effective therapeutic treatments for AD. We have identified SSH1, a phosphatase that activates Cofilin, as a promising therapeutic target for AD, as SSH1 impacts both A? and Tau. We have also identified several SSH1 inhibitor compounds that effectively decrease both A?-induced neurotoxicity and Tau hyperphosphorylation while decreasing A? production. In the proposal, we will perform chemical modifications of SSH1 inhibitor compounds to verify the functional groups critical for SSH1 inhibition and establish a platform for lead optimization. We will optimize and carry out in vitro phosphatase activity assays for SSH1 and other dual specificity phosphatases. We will also perform AD-relevant cell-based assays using existing and chemically modified compounds. Complex X-ray crystal structures will be determined using existing and modified compounds in physical contact with the catalytic domain of SSH1, to investigate the molecular basis of their interactions. Double perturbation experiments will be used to probe the contribution of specific inhibitor functional groups and protein residues to ligand binding using modified compounds and site-specific mutagenesis of SSH1. Based on a revised structural model, virtual docking and structure-based design will be performed to improve existing ligand efficiency, and new virtual screening will be carried out to identify additional SSH1 inhibitor chemotypes. Finally, based on the new structure-based ligand efficiency model, we will perform synthesis of a modified compound to demonstrate the proof-of-concept that such modified compound exhibits improved SSH1 inhibitory activity and ADME characteristics in vitro. Therefore, results of this R21 proposal are expected to yield valuable structure function relationship between SSH1 and existing and new compounds as well as establish a structure-based platform for extensive lead optimization and pharmacokinetic studies in a future R01 proposal.

Public Health Relevance

The defining pathological hallmark of Alzheimer's disease (AD) is the accumulation of A? and Tau in brain associated with synapse loss, mitochondrial dysfunction, cytoskeletal aberrations, and cognitive decline. We have identified a protein called SSH1, which promotes both A? and Tau pathologies, as a promising therapeutic target for AD. This application utilizes multiple integrated approaches in an effort to understand the structure-activity relationship between SSH1 and several SSH1 inhibitor compounds we have identified as well as to establish a structure-based platform for extensive lead optimization of compounds in future studies.

National Institute of Health (NIH)
National Institute on Aging (NIA)
Exploratory/Developmental Grants (R21)
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Drug Discovery for the Nervous System Study Section (DDNS)
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Refolo, Lorenzo
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University of South Florida
Schools of Medicine
United States
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Woo, Jung-A A; Liu, Tian; Trotter, Courtney et al. (2017) Loss of function CHCHD10 mutations in cytoplasmic TDP-43 accumulation and synaptic integrity. Nat Commun 8:15558
Woo, Jung A; Liu, Tian; Zhao, Xingyu et al. (2017) Enhanced tau pathology via RanBP9 and Hsp90/Hsc70 chaperone complexes. Hum Mol Genet 26:3973-3988
Liu, Tian; Wang, Fang; LePochat, Patrick et al. (2017) Cofilin-mediated Neuronal Apoptosis via p53 Translocation and PLD1 Regulation. Sci Rep 7:11532