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Biomedical subjects

Atsuhiro Kanayama

Publications and source records attributed to Atsuhiro Kanayama.

5 recordsLinked to original sources
PubMed2004

TAB2 and TAB3 activate the NF-kappaB pathway through binding to polyubiquitin chains.

The activation of NF-kappaB and IKK requires an upstream kinase complex consisting of TAK1 and adaptor proteins such as TAB1, TAB2, or TAB3. TAK1 is in turn activated by TRAF6, a RING domain ubiquitin ligase that facilitates the synthesis of lysine 63-linked polyubiquitin chains. Here we present evidence that TAB2 and TAB3 are receptors that bind preferentially to lysine 63-linked polyubiquitin chains through a highly conserved zinc finger (ZnF) domain. Mutations of the ZnF domain abolish the ability of TAB2 and TAB3 to bind polyubiquitin chains, as well as their ability to activate TAK1 and IKK. Significantly, replacement of the ZnF domain with a heterologous ubiquitin binding domain restored the ability of TAB2 and TAB3 to activate TAK1 and IKK. We also show that TAB2 binds to polyubiquitinated RIP following TNFalpha stimulation. These results indicate that polyubiquitin binding domains represent a new class of signaling domains that regulate protein kinase activity through a nonproteolytic mechanism.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Oxidation of Ikappa Balpha at methionine 45 is one cause of taurine chloramine-induced inhibition of NF-kappa B activation.

A band shift of IkappaBalpha was observed in Western blots with Jurkat cells treated with 1 mm taurine chloramine (TauCl) for 1 h. TauCl treatment inhibited tumor necrosis factor alpha (TNFalpha)-initiated nuclear factor kappaB (NF-kappaB) activation. TauCl did not inhibit either the upstream of IkappaB kinase (IKK) activation or IKK itself but did inhibit NF-kappaB activation induced by IKK overexpression. Deletion experiments showed that a TauCl modification site causing the band shift of IkappaBalpha is Met45. High performance liquid chromatography and mass spectrometry analyses of a small peptide containing Met45 revealed that TauCl oxidizes Met45. A mutant of IkappaBalpha whose Met45 was converted to alanine did not generate a band shift upon TauCl treatment and degraded in response to TNFalpha stimulation. However, a reporter assay revealed that NF-kappaB-dependent luciferase expression was not fully recovered in cells transfected with this mutant. These results indicate that Met45 oxidation of IkappaBalpha is a molecular mechanism underlying the TauCl-induced inhibition of NF-kappaB activation. A similar band shift was observed when HL-60 cells expressing myeloperoxidase were treated with 100 microm hydrogen peroxide for 5 min. When rat neutrophils were incubated with bacteria, intracellular taurine decreased interleukin-8 production. Therefore, taurine may help suppress excessive inflammatory reaction in neutrophils.

Amino Acid Substitution↗
PubMed2002

Suppression of the TNFalpha-induced increase in IL-1alpha expression by hypochlorite in human corneal epithelial cells.

PURPOSE: In response to injury, activated neutrophils release tumor necrosis factor (TNF)-alpha and myeloperoxidase (MPO). TNFalpha in turn causes human corneal epithelial cells to secrete interleukin (IL)-1alpha, whereas MPO results in formation of HClO/OCl(-). The effect of HClO/OCl(-) on the expression of the IL-1alpha gene and protein is unknown. The current study was undertaken to examine in immortalized human corneal epithelial cells whether NaOCl alters TNFalpha-induced increases in expression of IL-1alpha gene and protein. METHODS: Semiquantitative RT-PCR and ELISA characterized IL-1alpha gene and protein expression, respectively. TNFalpha-induced nuclear transfer of nuclear factor (NF)-kappaB was measured by electrophoretic mobility shift assay (EMSA). The alpha isoform of inhibitory protein kappaB (IkappaBalpha) was identified by Western blot analysis. RESULTS: Exposure to NaOCl (0.75 mM) for 10 minutes caused suppression of TNFalpha-induced increases in IL-1alpha mRNA and protein, declines in NFkappaB nuclear transfer, and a modification of IkappaBalpha, based on a bandshift detected by Western blot analysis. Modified IkappaBalpha became resistant to TNFalpha-induced proteolysis. Methionine sulfoxide reductase A (MsrA, 10 micro M) eliminated the NaOCl-induced IkappaBalpha bandshift. CONCLUSIONS; NaOCl oxidizes IkappaBalpha at methionine residues and thereby suppresses dissociation of IkappaBalpha from NFkappaB. Decreased dissociation could in turn suppress TNFalpha-induced activation of NFkappaB, resulting in declines in expression of IL-1alpha gene and protein. These effects suggest that release of HClO/OCl(-) in vivo by activated neutrophils may counterbalance TNFalpha-induced NFkappaB-dependent secretion if IL-1alpha and suppress an excessive inflammatory reaction.

Alkaline Phosphatase↗