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Mol. Cell. Biol., Jul 1997, 3884-3897, Vol 17, No. 7
T Nakamoto, R Sakai, H Honda, S Ogawa, H Ueno, T Suzuki, S Aizawa, Y Yazaki and H Hirai
p130cas (Cas) is an adapter protein that has an SH3 domain followed by
multiple SH2 binding motifs in the substrate domain. It also contains a
tyrosine residue and a proline-rich sequence near the C terminus, which are
the binding sites for the SH2 and SH3 domains of Src kinase, respectively.
Cas was originally identified as a major tyrosine- phosphorylated protein
in v-Crk- and v-Src-transformed cells. Subsequently, Cas was shown to be
inducibly tyrosine phosphorylated upon integrin stimulation; it is
therefore regarded as one of the focal adhesion proteins. Using an
immunofluorescence study, we examined the subcellular localization of Cas
and determined the regions required for its localization to focal
adhesions. In nontransformed cells, Cas was localized predominantly to the
cytoplasm and partially to focal adhesions. However, in
527F-c-Src-transformed cells, Cas was localized mainly to podosomes, where
the focal adhesion proteins are assembled. The localization of Cas to focal
adhesions was also observed in cells expressing the kinase-negative
527F/295M-c-Src. A series of analyses with deletion mutants expressed in
various cells revealed that the SH3 domain of Cas is necessary for its
localization to focal adhesions in nontransformed cells while both the SH3
domain and the C-terminal Src binding domain of Cas are required in
527F-c-Src-transformed cells and fibronectin-stimulated cells. In addition,
the localization of Cas to focal adhesions was abolished in Src-negative
cells. These results demonstrate that the SH3 domain of Cas and the
association of Cas with Src kinase play a pivotal role in the localization
of Cas to focal adhesions.
Copyright © 1997, American Society for Microbiology
Requirements for localization of p130cas to focal adhesions
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Japan.
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