Koichi Takimoto

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Neuropeptides are slowly released from a limited pool of secretory granules. To visualize this process, GFP-tagged preproatrial natriuretic factor (ANF) was expressed in nerve growth factor-treated PC12 cells. Biochemical and microfluorimetric experiments demonstrate that proANF-EGFP is packaged in granules that accumulate at neurite endings and is released(More)
The acidic environment inside secretory vesicles ensures that neuropeptides and peptide hormones are packaged in a concentrated condensed form. Although this is optimal for storage, decondensation limits release. Thus, it would be advantageous to alter the physical state of peptides in preparation for exocytosis. Here, we report that depolarization of the(More)
The Ca(2+)-binding proteins KChIP1-4 (KChIP3 is also known as DREAM and calsenilin) act as auxiliary subunits for voltage-gated K(+) channels in the Kv4 family. Here we identify three splicing isoforms of rat KChIP2 with variable N-terminal peptides. The two longer isoforms, which contain the 32-amino acid peptide, produce larger increases in Kv4.3 protein(More)
An asthma-related peptidase homologue (DPP10) may act as an auxiliary subunit of Kv4 channels, similar to DPPX. Here we show that DPP10 preferentially binds to Kv4 channel proteins to increase current density and alter channel gating. DPP10 also forms complexes by themselves and with DPPX in the absence of Kv4 channels. DPP10 mRNA is abundantly expressed in(More)
PDZ-domain-containing proteins such as PSD-95 have been implicated in the targeting and clustering of membrane proteins. Biochemical and immunohistochemical studies indicate that PSD-95 recognizes COOH-terminal S/TXV sequences present in Kv1 K+ channels. However, the effect of binding a PDZ domain on a target protein has not been studied in live cells. In(More)
Apoptosis in cortical neurons requires efflux of cytoplasmic potassium mediated by a surge in Kv2.1 channel activity. Pharmacological blockade or molecular disruption of these channels in neurons prevents apoptotic cell death, while ectopic expression of Kv2.1 channels promotes apoptosis in non-neuronal cells. Here, we use a cysteine-containing mutant of(More)
Degradation of lipid peroxides leads to the formation of cytotoxic 2-alkenals and oxenes (collectively designated reactive carbonyls). The novel NADPH-dependent oxidoreductase 2-alkenal reductase (AER; EC 1.3.1.74) from Arabidopsis (Arabidopsis thaliana), which is encoded by the gene At5g16970, catalyzes the reduction of the alpha,beta-unsaturated bond of(More)
Voltage-gated potassium (Kv) channels play important roles in differentiation and growth of non-excitable cells. Inhibition of these channels is also known to suppress proliferation of various cancer cells. Here we examine expression of K+ channel subunit genes in various uterine cancer cells and their roles in cell proliferation. RT-PCR analysis reveals(More)
P1-zeta-crystallin (P1-ZCr) is an oxidative stress-induced NADPH:quinone oxidoreductase in Arabidopsis thaliana, but its physiological electron acceptors have not been identified. We found that recombinant P1-ZCr catalyzed the reduction of 2-alkenals of carbon chain C(3)-C(9) with NADPH. Among these 2-alkenals, the highest specificity was observed for(More)
PURPOSE In an effort to assess the characteristics of mutation induced by different linear energy transfer (LET) radiation in higher plants, the mutational effects of carbon-ion beams and gamma-rays were investigated in Arabidopsis. MATERIALS AND METHODS The rpsL (Escherichia coli ribosomal protein small subunit S12) transgenic Arabidopsis(More)