Oligomerizing potential of a focal adhesion LIM protein Hic-5 organizing a nuclear-cytoplasmic shuttling complex.
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.
Mori
Kazunori
K
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan.
Asakawa
Masayuki
M
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan.
Hayashi
Miki
M
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan.
Imura
Miwako
M
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan.
Ohki
Takahiro
T
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan.
Hirao
Etsuko
E
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan.
Kim-Kaneyama
Joo-Ri
JR
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan.
Nose
Kiyoshi
K
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan.
Shibanuma
Motoko
M
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo 142-8555, Japan. Electronic address: smotoko@pharm.showa-u.ac.jp.
D021581:Active Transport, Cell Nucleus; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D049109:Cell Proliferation; D003598:Cytoskeletal Proteins / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D019281:Dimerization; D022001:Focal Adhesions; D018398:Homeodomain Proteins / Q000502:physiology; D060588:LIM Domain Proteins; D008565:Membrane Proteins; D051379:Mice; D046912:Multiprotein Complexes; D011485:Protein Binding; D017434:Protein Structure, Tertiary
D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; C490232:Lims1 protein, mouse; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C090090:Tgfb1i1 protein, mouse