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The Sos1-Rac1 signaling - Possible involvement of a vacuolar H+ -ATPase E subunit

  1. Author:
    Miura, K.
    Miyazawa, S.
    Furuta, S.
    Mitsushita, J.
    Kamijo, K.
    Ishida, H.
    Miki, T.
    Suzukawa, K.
    Resau, J.
    Copeland, T. D.
    Kamata, T.

  2. Author Address

    Shinshu Univ, Sch Med, Dept Mol Biol & Biochem, Asahi 3-1-1, Matsumoto, Nagano 3908621, Japan. Shinshu Univ, Sch Med, Dept Mol Biol & Biochem, Matsumoto, Nagano 3908621, Japan. Sci Applicat Int Corp, SAIC Frederick, Frederick, MD 21702 USA. NCI, Frederick Canc Res & Dev Ctr, Adv BioSci Labs, NIH, Frederick, MD 21702 USA. NCI, Basic Res Lab, NIH, Bethesda, MD 20892 USA. Kamata T Shinshu Univ, Sch Med, Dept Mol Biol & Biochem, Asahi 3-1-1, Matsumoto, Nagano 3908621, Japan.
    1. Year: 2001
  2. Journal: Journal of Biological Chemistry
    1. 276
    2. 49
    3. Pages: 46276-46283
  4. Type of Article: Article
  1. Abstract:

    We have purified and identified a 32-kDa protein interacting with the Dbl oncogene homology domain of mSos1(Sos-DH) from rat brains by glutathione S-transferase-Sos-DH affinity chromatography. Peptide sequencing revealed that the protein is identical to a positive regulatory E subunit (V-ATPase E) of a vacuolar H+-ATPase, which is responsible for acidification of endosome and alkalinization of intracellular pH. The interaction between V-ATPase E and Sos-DH was confirmed by yeast two-hybrid assay. A coimmunoprecipitation assay demonstrated that a V-ATPase E protein physiologically bound to mSos1, and the protein was colocalized with mSos1 in the cytoplasm, as determined by immunohistochemistry. mSos1 was found in the early endosome fraction together with V-ATPase E and Rac1, suggesting the functional involvement of mSos1/V- ATPase E complexes in the Rac1 activity at endosomes. Overexpression of V-ATPase E in COS cells enhanced the ability of mSos1 to promote the guanine nucleotide exchange activity for Rac1 and stimulated the kinase activity of Jun kinase, a downstream target of Rac1. Thus, the data indicate that V- ATPase E may participate in the regulation of the mSos1- dependent Rac1 signaling pathway involved in growth factor receptor-mediated cell growth control.

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