Dephosphorylation of endogenous GABA(B) receptor R2 subunit and AMPK α subunits which were measured by in vitro method using transfer membrane.

Protein phosphorylation can be regulated by changes in kinase activity, phosphatase activity, or both. GABA(B) receptor R2 subunit (GABA(B)R2) is phosphorylated at S783 by 5'-AMP-activated-protein kinase (AMPK), and this phosphorylation modulates GABA(B) receptor desensitization. Since the GABA(B) receptor is an integral membrane protein, solubilizing GABA(B)R2 is difficult. To circumvent this problem and to identify specific phosphatases that dephosphorylate S783, we employed an in vitro assay based on dephosphorylation of proteins on PVDF membranes by purified phosphatases. Our method allowed us to demonstrate that S783 in GABA(B)R2 is directly dephosphorylated by PP2A (but not by PP1, PP2B nor PP2C) in a dose-dependent and okadaic acid-sensitive manner. We also show that the level of phosphorylation of the catalytic subunit of AMPK at T172 is reduced by PP1, PP2A and PP2C. Our data indicate that PP2A dephosphorylates GABA(B)R2(S783) less efficiently than AMPK(T172), and that additional phosphatases might be involved in S783 dephosphorylation.

[Case of Vogt-Koyanagi-Harada disease associated with non-herpetic acute limbic encephalitis with autoantibodies against glutamate receptor epsilon2 in the cerebrospinal fluid].

We report a case of Vogt-Koyanagi-Harada (VKH) disease associated with non-herpetic acute limbic encephalitis with autoantibodies against glutamate receptor epsilon2 in the cerebrospinal fluid. A 42-year-old woman developed a complaint of visual distortion, visual disturbance, headache and mild psychiatric symptoms, such as anxiety and depression. She was diagnosed as VKH through the fidings of fluorescein fundus angiography, which revealed patchy hypofluorescence associated with delayed choroidal filling at early fluorescein angiographic phase, and spotted choroidal hyperfluorescence and pooling of dye at late phase. Analysis of the cerebrospinal fluid (CSF) showed slight increase of leukocyte count (49/microl, mononuclear cells) and immunoglobulin (Ig) G index. An anti-GluRepsilon2 IgM antibody was positive in CSF. Brain magnetic resonance imaging (MRI) showed a monofocal hyperintensity lesion in the left parahippocampal gyrus on T2-weighted and fluid-attenuated inversion recovery (FLAIR) images. We diagnosed her VKH disease associated with non-herpetic acute limbic encephalitis. She was treated with oral prednisone, 70 mg day and her symptoms have gradually improved. To our knowledge, meningoencephalitis in VKH disease is extremely rare and the analysis of anti-GluRepsilon2 IgM antibody in CSF has not been reported. We speculate that a certain immunologic mechanism, including the anti-GluRepsilon2 IgM antibody, contributes to the pathogenesis of the VKH disease with non-herpetic acute limbic encephalitis.

Expression of THR1, a 1,3,8-trihydroxynaphthalene reductase gene involved in melanin biosynthesis in the phytopathogenic fungus Bipolaris oryzae, is enhanced by near-ultraviolet radiation.

1,3,8-Trihydroxynaphthalene (1,3,8-THN) reductase is involved in the production of fungal dihydroxynaphthalene (DHN) melanin. We isolated and characterized THR1, a gene encoding 1,3,8-THN reductase, from the phytopathogenic fungus Bipolaris oryzae. Sequence analysis showed that THR1 encodes a putative protein of 267 amino acids having a molecular weight of 28.5 kDa and 68-98% sequence identity to other fungal 1,3,8-THN reductases. Targeted disruption of the THR1 gene showed that it is essential for melanin biosynthesis in B. oryzae. Northern blot analysis showed that THR1 transcripts are constitutively expressed during normal growth but are specifically enhanced by near-ultraviolet (NUV) radiation in a dose-dependent manner. These results indicate that THR1 expression is transcriptionally enhanced by NUV radiation in B. oryzae.