Biochemistry and Pharmacology - Research Publications

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Start date: 2020 × Author: Cheng, Heung ×

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    N-Terminomic Changes in Neurons During Excitotoxicity Reveal Proteolytic Events Associated With Synaptic Dysfunctions and Potential Targets for Neuroprotection
    Ameen, SS ; Griem-Krey, N ; Dufour, A ; Hossain, MI ; Hoque, A ; Sturgeon, S ; Nandurkar, H ; Draxler, DF ; Medcalf, RL ; Kamaruddin, MA ; Lucet, IS ; Leeming, MG ; Liu, D ; Dhillon, A ; Lim, JP ; Basheer, F ; Zhu, H-J ; Bokhari, L ; Roulston, CL ; Paradkar, PN ; Kleifeld, O ; Clarkson, AN ; Wellendorph, P ; Ciccotosto, GD ; Williamson, NA ; Ang, C-S ; Cheng, H-C (ELSEVIER, 2023-05)
    Excitotoxicity, a neuronal death process in neurological disorders such as stroke, is initiated by the overstimulation of ionotropic glutamate receptors. Although dysregulation of proteolytic signaling networks is critical for excitotoxicity, the identity of affected proteins and mechanisms by which they induce neuronal cell death remain unclear. To address this, we used quantitative N-terminomics to identify proteins modified by proteolysis in neurons undergoing excitotoxic cell death. We found that most proteolytically processed proteins in excitotoxic neurons are likely substrates of calpains, including key synaptic regulatory proteins such as CRMP2, doublecortin-like kinase I, Src tyrosine kinase and calmodulin-dependent protein kinase IIβ (CaMKIIβ). Critically, calpain-catalyzed proteolytic processing of these proteins generates stable truncated fragments with altered activities that potentially contribute to neuronal death by perturbing synaptic organization and function. Blocking calpain-mediated proteolysis of one of these proteins, Src, protected against neuronal loss in a rat model of neurotoxicity. Extrapolation of our N-terminomic results led to the discovery that CaMKIIα, an isoform of CaMKIIβ, undergoes differential processing in mouse brains under physiological conditions and during ischemic stroke. In summary, by identifying the neuronal proteins undergoing proteolysis during excitotoxicity, our findings offer new insights into excitotoxic neuronal death mechanisms and reveal potential neuroprotective targets for neurological disorders.
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    The structure of the extracellular domains of human interleukin 11? receptor reveals mechanisms of cytokine engagement
    Metcalfe, RD ; Aizel, K ; Zlatic, CO ; Nguyen, PM ; Morton, CJ ; Lio, DS-S ; Cheng, H-C ; Dobson, RCJ ; Parker, MW ; Gooley, PR ; Putoczki, TL ; Griffin, MDW (AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2020-06-12)
    Interleukin (IL) 11 activates multiple intracellular signaling pathways by forming a complex with its cell surface α-receptor, IL-11Rα, and the β-subunit receptor, gp130. Dysregulated IL-11 signaling has been implicated in several diseases, including some cancers and fibrosis. Mutations in IL-11Rα that reduce signaling are also associated with hereditary cranial malformations. Here we present the first crystal structure of the extracellular domains of human IL-11Rα and a structure of human IL-11 that reveals previously unresolved detail. Disease-associated mutations in IL-11Rα are generally distal to putative ligand-binding sites. Molecular dynamics simulations showed that specific mutations destabilize IL-11Rα and may have indirect effects on the cytokine-binding region. We show that IL-11 and IL-11Rα form a 1:1 complex with nanomolar affinity and present a model of the complex. Our results suggest that the thermodynamic and structural mechanisms of complex formation between IL-11 and IL-11Rα differ substantially from those previously reported for similar cytokines. This work reveals key determinants of the engagement of IL-11 by IL-11Rα that may be exploited in the development of strategies to modulate formation of the IL-11-IL-11Rα complex.