Cortical GluK1 kainate receptors modulate scratching in adult mice

Recent investigations into the mechanisms mediating itch transmission have focused on spinal mechanisms, whereas few studies have investigated the role of the cerebral cortex in itch‐related behaviors. Human imaging studies show that several cortical regions are active in correspondence with itch, including the anterior cingulate cortex (ACC). We present here evidence of cortical modulation of pruritogen‐induced scratching behavior. We combine pharmacological, genetic, and electrophysiological approaches to show that cortical GluK1‐containing kainate (KA) receptors are involved in scratching induced by histamine and non‐histamine‐dependent itching stimuli. We further show that scratching corresponds with enhanced excitatory transmission in the ACC through KA receptor modulation of inhibitory circuitry. In addition, we found that inhibiting GluK1‐containing KA receptors in the ACC also reduced behavioral nociceptive responses induced by formalin. Our results reveal a new role of the cortex in pruritogen‐induced scratching.

     

Novel Twin Streptolysin S-Like Peptides Encoded in the sag Operon Homologue of Beta-Hemolytic Streptococcus anginosus

Streptococcus anginosus is a member of the anginosus group streptococci, which form part of the normal human oral flora. In contrast to the pyogenic group streptococci, our knowledge of the virulence factors of the anginosus group streptococci, including S. anginosus, is not sufficient to allow a clear understanding of the basis of their pathogenicity. Generally, hemolysins are thought to be important virulence factors in streptococcal infections. In the present study, a sag operon homologue was shown to be responsible for beta-hemolysis in S. anginosus strains by random gene knockout. Interestingly, contrary to pyogenic group streptococci, beta-hemolytic S. anginosus was shown to have two tandem sagA homologues, encoding streptolysin S (SLS)-like peptides, in the sag operon homologue. Gene deletion and complementation experiments revealed that both genes were functional, and these SLS-like peptides were essential for beta-hemolysis in beta-hemolytic S. anginosus. Furthermore, the amino acid sequence of these SLS-like peptides differed from that of the typical SLS of S. pyogenes, especially in their propeptide domain, and an amino acid residue indicated to be important for the cytolytic activity of SLS in S. pyogenes was deleted in both S. anginosus homologues. These data suggest that SLS-like peptides encoded by two sagA homologues in beta-hemolytic S. anginosus may be potential virulence factors with a different structure essential for hemolytic activity and/or the maturation process compared to the typical SLS present in pyogenic group streptococci.     

Glu-44 in the Amino-terminal α-Helix of Yeast Vacuolar ATPase E Subunit (Vma4p) Has a Role for VoV1 Assembly

The proton (H⁺) pumping vacuolar-type ATPase (V-ATPase) is a rotary enzyme that plays a pivotal role in forming intracellular acidic compartments in eukaryotic cells. In Saccharomyces cerevisiae, the membrane extrinsic catalytic V₁ and the transmembrane proton-pumping V_o complexes have been shown to reversibly dissociate upon removal of glucose from the medium. However, the basis of this disassembly is largely unknown. In the earlier study, we have found that the amino-terminal α-helical domain between Lys-33 and Lys-83 of yeast E subunit (Vma4p) in the peripheral stalk of the V₁ complex has a role in glucose-dependent V_oV₁ assembly. Results of alanine-scanning mutagenesis within the domain revealed that the Vma4p Glu-44 is a key residue in V_oV₁ disassembly. Biochemical analysis on Vma4p Glu-44 to Ala, Asn, Asp, and Gln substitutions indicated that Glu-44 has a role in V-ATPase catalysis. These results suggest that Glu-44 is one of the key functional residues for subunit interaction in the V-ATPase stalk complex that allows both efficient rotation catalysis and assembly.     

Connexin-43 hemichannels contribute to the propagation of μ-calpain-mediated neuronal death in a cortical ablation injury model

We investigated the role of the astrocytic and neuronal hemichannels (HCs) in the spread of cortical neuronal death in a rat cortical injury model. Over time (by 6 h), propidium iodide (PI)-positive cells with labeling either with anti-neuron specific enolase or anti-parvalbumin (indicating GABAnergic interneurons) antibody spread in the deep cortical layers adjacent to the injury and co-localized with activated μ-calpain. Connexin (Cx)-43, glial fibrillary acidic protein (GFAP), activated μ-calpain and α-fodrin breakdown product (FBP) increased post-injury, peaking at 1 h, in the injury and adjacent areas. GFAP-Cx43-positive reactivated astrocytes exhibited similar distribution to the dead neurons. Cx43 and Cx36 primarily comprise HCs in the astrocyte and neuron, respectively. Ethidium bromide (EtBr) uptake was enhanced post-injury, and confirmed in the Cx43- and Cx36-positive cells. A Cx43-HC inhibitor Gap26 prevented the opening of the Cx43-HC and Cx36-HC, μ-calpain activation, α-fodrin proteolysis and death in the deep cortical neurons. Collectively, opening of the astrocytic Cx43-HC and neuronal Cx36-HC would induce the regional spread of cortical neuronal death through μ-calpain activation in the rat brain injury model.     

Real-Time Visualization of Neuronal Activity during Perception

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Formation of long-chain N-vanillyl-acylamides from plant oils

Long-chain N-vanillyl-acylamides (LCNVAs) were generated from plant oils and vanillylamine (VA) by nucleophilic amidation without any catalytic reagents. The resulting LCNVAs varied according to the fatty acid composition of the plant oil used. Therefore, the LCNVAs contained in Capsicum oleoresins were products that were spontaneously generated from the oleoresin during storage.     

Identification of Highly Selective and Potent Histone Deacetylase 3 Inhibitors Using Click Chemistry-Based Combinatorial Fragment Assembly

To find histone deacetylase 3 (HDAC3)-selective inhibitors, a series of 504 candidates was assembled using “click chemistry”, by reacting nine alkynes bearing a zinc-binding group with 56 azide building blocks in the presence of Cu(I) catalyst. Screening of the 504-member triazole library against HDAC3 and other HDAC isozymes led to the identification of potent and selective HDAC3 inhibitors T247 and T326. These compounds showed potent HDAC3 inhibition with submicromolar IC₅₀s, whereas they did not strongly inhibit other isozymes. Compounds T247 and T326 also induced a dose-dependent selective increase of NF-κB acetylation in human colon cancer HCT116 cells, indicating selective inhibition of HDAC3 in the cells. In addition, these HDAC3-selective inhibitors induced growth inhibition of cancer cells, and activated HIV gene expression in latent HIV-infected cells. These findings indicate that HDAC3-selective inhibitors are promising candidates for anticancer drugs and antiviral agents. This work also suggests the usefulness of the click chemistry approach to find isozyme-selective HDAC inhibitors.