Biology subjects

Cheng, S.-J.

Publications and source records attributed to Cheng, S.-J..

3 recordsLinked to original sources

bioRxiv2021

Crystal structures and functional analysis of the ZnF5-WWE1-WWE2 region of PARP13/ZAP define a new mode of engaging poly(ADP-ribose)

PARP13/ZAP acts against multiple viruses through recognizing and promoting degradation of cytoplasmic viral mRNA. PARP13 has four N-terminal Zn-finger motifs that bind CG-rich nucleotide sequences, and a C-terminal ADP ribosyltransferase fold similar to other PARPs. A central region predicted to contain a fifth Zn-finger and two tandem WWE domains is implicated in binding poly(ADP-ribose); however, there are limited insights into the structure and function of this PARP13 region (ZnF5-WWE1-WWE2). Here, we present crystal structures of ZnF5-WWE1-WWE2 from mouse PARP13 in complex with ADP-ribose and with ATP. ZnF5-WWE1-WWE2 crystallized as a dimer with major contacts formed between WWE1 and WWE2 originating from different monomers, indicative of a more compact monomeric arrangement of the tandem WWE domains. Solution scattering experiments and biophysical analysis indicated a monomer in solution, suggesting that the crystal dimer represents domain swapping that could potentially represent a PARP13 conformation assumed when signaling viral RNA detection. The crystal structure and binding studies demonstrate that WWE2 interacts with ADP-ribose and ATP, whereas WWE1 does not have a functional binding site. The shape of the WWE2 binding pocket disfavors interaction with the ribose-ribose linkage of poly(ADP-ribose). Binding studies with poly(ADP-ribose) ligands indicate that WWE2 serves as an anchor for preferential binding to the terminal end of poly(ADP-ribose), and the composite structure of ZnF5-WWE1-WWE2 forms an extended surface to engage polymer chains of ADP-ribose. This model represents a novel mode of poly(ADP-ribose) recognition and provides a structural framework for investigating poly(ADP-ribose) impact on PARP13 function.

biochemistry↗

bioRxiv2021

High-throughput Activity Assay for Screening Inhibitors of the SARS-CoV-2 Mac1 Macrodomain

Macrodomains are a class of conserved ADP-ribosylhydrolases expressed by viruses of pandemic concern, including coronaviruses and alphaviruses. Viral macrodomains are critical for replication and virus-induced pathogenesis; therefore, these enzymes are a promising target for antiviral therapy. However, no potent or selective viral macrodomain inhibitors currently exist, in part due to the lack of a high-throughput assay for this class of enzymes. Here, we developed a high-throughput ADP-ribosylhydrolase assay using the SARS-CoV-2 macrodomain Mac1. We performed a pilot screen which identified dasatinib and dihydralazine as ADP-ribosylhydrolase inhibitors. Importantly, dasatinib does not inhibit MacroD2, the closest Mac1 homolog in humans. Our study demonstrates the feasibility of identifying selective inhibitors based on ADP-ribosylhydrolase activity, paving the way for screening large compound libraries to identify improved macrodomain inhibitors and explore their potential as antiviral therapies for SARS-CoV-2 and future viral threats.

biochemistry↗

bioRxiv2020

A novel equilibrative nucleoside transporter 1 inhibitor alleviates Tau-mediated neurodegeneration

Tau hyperphosphorylation favors the formation of neurofibrillary tangles and triggers the gradual loss of neuronal functions in tauopathies, including Alzheimers disease. Herein, we demonstrated that chronic treatment with an inhibitor (J4) of equilibrative nucleoside transporter 1 (ENT1), which plays a critical role in controlling adenosine homeostasis and purine metabolism in the brain, exerted beneficial effects in a mouse model of tauopathy (Thy-Tau22, Tau22). Chronic treatment with J4 improved spatial memory deficits, mitochondrial dysfunction, synaptic plasticity impairment, and gliosis. Immunofluorescence assays showed that J4 not only reduced Tau hyperphosphorylation but also normalized the reduction in mitochondrial mass and suppressed the abnormal activation of AMP-activated protein kinase (AMPK), a pathogenic feature that is also observed in the brains of patients with tauopathies. Given that AMPK is an important energy sensor, our findings suggest that energy dysfunction is associated with tauopathy and that J4 may exert its protective effect by improving energy homeostasis. Bulk RNA-seq analysis revealed that J4 also mitigated immune signature associated with Tau pathology including C1q upregulation and A1 astrocyte markers. Collectively, our findings suggest that identifying strategies for normalizing energy and neuroimmune dysfunctions in tauopathies through adenosinergic signaling modulation may pave the way for the development of treatments for Alzheimers disease.

neuroscience↗