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ER-resident Gi2 protein controls sar1 translocation onto the ER during budding of transport vesicles

Authors

  • Hiroshi Nakagawa,

    1. Laboratory of Toxicology, Course of Veterinary Science, Graduate School of Life and Environmental Biosciences, Osaka Prefecture University, Osaka, Japan
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  • Haruka Umadome,

    1. Laboratory of Toxicology, Course of Veterinary Science, Graduate School of Life and Environmental Biosciences, Osaka Prefecture University, Osaka, Japan
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  • Shuichi Miyazaki,

    1. The Center for Advanced Research, Graduate School of Medical Sciences, Toho University, Tokyo, Japan
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  • Katsuhiro Tanaka,

    1. Laboratory of Cellular and Molecular Biology, Course of Veterinary Science, Graduate School of Life and Environmental Biosciences, Osaka Prefecture University, Osaka, Japan
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  • Kazuhiko Nishimura,

    1. Laboratory of Toxicology, Course of Veterinary Science, Graduate School of Life and Environmental Biosciences, Osaka Prefecture University, Osaka, Japan
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  • Masayuki Komori,

    1. Laboratory of Cellular and Molecular Biology, Course of Veterinary Science, Graduate School of Life and Environmental Biosciences, Osaka Prefecture University, Osaka, Japan
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  • Saburo Matsuo

    Corresponding author
    1. Laboratory of Toxicology, Course of Veterinary Science, Graduate School of Life and Environmental Biosciences, Osaka Prefecture University, Osaka, Japan
    • Laboratory of Toxicology, Course of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58, Rinku-Orai-Kita, Izumisano, Osaka 598-8531, Japan.
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Abstract

In our previous study, fluoride ([AlF4]) disturbed ER-to-Golgi transport through the activation of ER-resident heterotrimeric G protein (ER-G protein). Therefore, ER-G protein may be implicated in ER-to-Golgi transport at the early stage prior to coat protein assembly. Sar1 translocation onto the endoplasmic reticulum (ER) membrane is suppressed by non-selective protein kinase inhibitor H89, suggesting the participation of H89-sensitive kinase in this process. To investigate the involvement of ER-G protein in ER-to-Golgi transport, the effect of Gi protein activator (mastoparan 7) was examined on Sar1 translocation onto the ER in a cell-free system consisting of microsome membrane and cytosol. Sar1 translocation onto the microsome membrane was induced by addition of GTPγS in the cell-free system. Translocation of Sar1 by GTPγS was suppressed significantly by both H89 and mastoparan 7. Mastoparan 7 suppressed the translocation of Sar1 onto the microsome membrane with dosage dependency, but mastoparan 17, the inactive analog of mastoparan 7, had no effect on Sar1 translocation. The suppressive effect of mastoparan 7 was recovered by treatment with pertussis toxin (IAP). Moreover, Gi2 protein was detected on the microsome membrane by western blotting for heterotrimeric Gi proteins. These results indicate that ER-Gi2 protein modulated Sar1 translocation onto the ER, suggesting that ER-resident Gi2 protein is an important negative regulator of vesicular transport at the early stage of vesicle formation before coat protein assembly on the ER. J. Cell. Biochem. 112: 2250–2256, 2011. © 2011 Wiley-Liss, Inc.

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