title: Flavonoids from Radix Scutellariae as potential stroke therapeutic agents by targeting the second postsynaptic density 95 (PSD-95)/disc large/zonula occludens-1 (PDZ) domain of PSD-95.
abstract: Excessive activation of N-methyl-D-aspartate receptors (NMDARs) and subsequent production of nitric oxide by neuronal nitric oxide synthase (nNOS) contribute to neuronal damage resulting from hypoxic and ischemic insults. NMDARs and nNOS are coupled together at the postsynaptic membrane through their interaction with postsynaptic density protein (PSD) 95 via PSD-95/disc large/zonula occludens-1 (PDZ) domains. We used NMR (nuclear magnetic resonance) spectroscopy to screen medicinal herbs used in traditional Chinese medicine (TCM) stroke therapy for compounds binding to the second PDZ domain (PDZ2) of PSD-95, the domain linking nNOS and PSD-95. Aqueous extract of Huangqin, the root of Scutellaria baicalensis Georgi (Labiatae), showed significant binding to PDZ2 of PSD-95. The binding site of the active components in the extract overlapped with the nNOS/NR2B-binding pocket of PDZ2 of PSD-95. Four flavones, baicalin, norwogonoside, oroxylin A-glucuronide (oroxyloside), and wogonoside were isolated and found to account for the PDZ-binding activity of the extract. NMR titration experiments showed that baicalin and norwogonoside displayed the highest PDZ2 binding affinity, while oroxylin A-glucuronide and wogonoside showed 4-5 fold less potency in binding to the PDZ domain. Identification of the PDZ binding activity of these compounds will allow investigating whether or not it contributes to the observed clinical effects of Radix Scutellariae. Furthermore, these molecules might provide leads for the development of drugs targeting the signaling pathways mediated by PDZ domains.
authors.affiliation: Department of Biology, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China.
authors.forename: W
authors.initials: W
authors.lastname: Tang
authors.forename: X
authors.initials: X
authors.lastname: Sun
authors.forename: J S
authors.initials: JS
authors.lastname: Fang
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: N J
authors.initials: NJ
authors.lastname: Sucher
mesh_terms: D000818:Animals; D000076122:Disks Large Homolog 4 Protein; D005419:Flavonoids / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D047908:Intracellular Signaling Peptides and Proteins; D019686:Lamiaceae; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D008517:Phytotherapy; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D018517:Plant Roots; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D020521:Stroke / Q000517:prevention & control
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D005419:Flavonoids; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010936:Plant Extracts; D016194:Receptors, N-Methyl-D-Aspartate; C033652:postsynaptic density proteins; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat