• Open Access

LIM domain-containing adaptor, leupaxin, localizes in focal adhesion and suppresses the integrin-induced tyrosine phosphorylation of paxillin

Authors

  • Toshiyuki Tanaka,

    Corresponding author
    1. Laboratory of Immunodynamics, Department of Microbiology and Immunology, Osaka University, Graduate School of Medicine, Osaka
      3To whom correspondence should be addressed.
      E-mail: tanaka@huhs.ac.jp
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    • 4

      Present address: Laboratory of Immunobiology, Department of Pharmacy, School of Pharmacy, Hyogo University of Health Sciences, Kobe, Japan.

  • Kazumasa Moriwaki,

    1. Laboratory of Immunodynamics, Department of Microbiology and Immunology, Osaka University, Graduate School of Medicine, Osaka
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    • 5

      Present address: Division of Vascular Biology, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan.

  • Shinsuke Murata,

    1. Laboratory of Immunodynamics, Department of Microbiology and Immunology, Osaka University, Graduate School of Medicine, Osaka
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  • Masayuki Miyasaka

    1. Laboratory of Immunodynamics, Department of Microbiology and Immunology, Osaka University, Graduate School of Medicine, Osaka
    2. Laboratory of Immunodynamics, WPI Immunology Frontier Research Center, Osaka University, Osaka, Japan
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3To whom correspondence should be addressed.
E-mail: tanaka@huhs.ac.jp

Abstract

Focal adhesion (FA) consists of multiple cellular proteins including paxillin and serves as a center for adhesion-mediated signaling. The assembly and disassembly of FAs is regulated by locally produced intracellular signals, and tyrosine phosphorylation of paxillin has been implicated in this process. A Lin-11 Isl-1 Mec-3 (LIM) domain-containing adaptor protein, leupaxin, a member of the paxillin family, is expressed in leukocytes as well as in certain cancer cells, and shares overall structural characteristics with paxillin. However, it remains unknown whether leupaxin and paxillin cooperate with or antagonize each other in integrin signaling. Here we show that leupaxin potently represses the tyrosine phosphorylation of paxillin. When expressed in mouse thymoma BW5147 cells bound to ICAM-1, leupaxin accumulated in FA-like patches in the cell periphery. When expressed in NIH3T3 and HEK293T cells, leupaxin localized to FAs upon cell adhesion to fibronectin and strongly suppressed the integrin-induced tyrosine phosphorylation of paxillin. In integrin-stimulated HEK293T cells, leupaxin’s LIM3 domain appeared essential for selective FA localization and the suppression of paxillin tyrosine phosphorylation. Leupaxin’s LD3 motif, which is critical for stable association with FAK, was dispensable for leupaxin’s suppressive ability. In addition, leupaxin reduced the spreading of NIH3T3 cells on fibronectin, which required both the LD3 motif and LIM3 domain. When expressed in human leukocytic K562 cells, leupaxin significantly suppressed integrin α5β1-mediated cell adhesion to fibronectin and the tyrosine phosphorylation of paxillin. These findings indicate that leupaxin functions as a paxillin counterpart that potently suppresses the tyrosine phosphorylation of paxillin during integrin signaling. (Cancer Sci 2009)

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