Oligomerizing potential of a focal adhesion LIM protein Hic-5 organizing a nuclear-cytoplasmic shuttling complex

J Biol Chem. 2006 Aug 4;281(31):22048-22061. doi: 10.1074/jbc.M513111200. Epub 2006 May 31.

Abstract

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, LIM4. 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 integrin-linked kinase, 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 integrin-linked kinase. 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus*
  • Adaptor Proteins, Signal Transducing
  • Animals
  • Cell Adhesion
  • Cell Line
  • Cell Proliferation
  • Cytoskeletal Proteins / physiology*
  • DNA-Binding Proteins / physiology*
  • Dimerization
  • Focal Adhesions
  • Homeodomain Proteins / physiology
  • LIM Domain Proteins
  • Membrane Proteins
  • Mice
  • Multiprotein Complexes
  • Protein Binding
  • Protein Structure, Tertiary

Substances

  • Adaptor Proteins, Signal Transducing
  • Cytoskeletal Proteins
  • DNA-Binding Proteins
  • Homeodomain Proteins
  • LIM Domain Proteins
  • Lims1 protein, mouse
  • Membrane Proteins
  • Multiprotein Complexes
  • Tgfb1i1 protein, mouse