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A more recent version of this article appeared on August 4, 2006
Papers In Press, published online ahead of print May 31, 2006
J. Biol. Chem, 10.1074/jbc.M513111200
Submitted on December 8, 2005
Revised on May 22, 2006
Accepted on May 30, 2006
Oligomerizing potential of a focal adhesion LIM protein Hic-5 organizing a nuclear-cytoplasmic shuttling complex
Kazunori Mori, Masayuki Asakawa, Miki Hayashi, Miwako Imura, Takahiro Ohki, Etsuko Hirao, Joo-ri Kim Kaneyama, Kiyoshi Nose, and Motoko Shibanuma
Microbiology, Showa University School of Pharmaceutical Sciences, Shinagawa-ku, Tokyo
Corresponding Author: smotoko{at}pharm.showa-u.ac.jp
Hic-5 is a focal adhesion LIM protein serving as a scaffold in integrin signaling. The protein comprises four LD domains in its N-terminal half and four LIM domains in its C-terminal half with a nuclear export signal in LD3, and is shuttled between the cytoplasmic and nuclear compartments. In this study, immunoprecipitation and in vitro cross-linking experiments showed that Hic-5 homo-oligomerized through its most C-terminal LIM domain, LIM 4. Strikingly, paxillin, the protein most homologous to Hic-5, did not show this capability. Gel filtration analysis also revealed that Hic-5 differs from paxillin in that it has multiple forms in the cellular environment, and Hic-5 but not paxillin was capable of hetero-oligomerization with a LIM-only protein, PINCH, another molecular scaffold at focal adhesions. The fourth LIM domain of Hic-5 and the fifth LIM domain region of PINCH constituted the interface for the interaction. The complex included ILK, a binding partner of PINCH, which also interacted with Hic-5 through the region encompassing the pleckstrin homology-like domain and LIM domains of Hic-5. Of note, Hic-5 marginally affected the subcellular distribution of PINCH but directed its shuttling between the cytoplasmic and nuclear compartments in the presence of ILK. Uncoupling of the two signaling platforms of Hic-5 and PINCH through interference with the hetero-oligomerization resulted in impairment of cellular growth. Hic-5 is, thus, a molecular scaffold with the potential to dock with another scaffold through the LIM domain, organizing a mobile supramolecular unit and coordinating the adhesion signal with cellular activities in the two compartments.

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K. Mori, E. Hirao, Y. Toya, Y. Oshima, F. Ishikawa, K. Nose, and M. Shibanuma
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Copyright © 2006 by the American Society for Biochemistry and Molecular Biology.
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