FAP52, a Novel, SH3 Domain-containing Focal Adhesion Protein

Jari Meriläinen,Veli-Pekka Lehto,Veli-Matti Wasenius

doi:10.1074/jbc.272.37.23278

Jari Meriläinen, Veli-Pekka Lehto + Show 1 more

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https://doi.org/10.1074/jbc.272.37.23278

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Abstract

Src-homology 3 (SH3) domain is a 60-70-amino acid motif present in a large variety of signal transduction and cytoskeletal proteins. We used reverse transcriptase-polymerase chain reaction with degenerate and specific primers and chicken brain mRNA to clone a cDNA that codes for a novel SH3 domain-containing protein. The sequence predicts a 448-amino acid polypeptide with a molecular mass of 51, 971 daltons. In the amino terminus, it shows a very high propensity for alpha-helicity, suggesting coiled-coil and possibly a higher order oligomeric arrangement. In the carboxyl terminus, there is a unique SH3 sequence. In Northern blotting, a major 3.7-kilobase and a minor 7.2-kilobase transcript was detected in most chicken tissues. In immunofluorescence microscopy and immunoelectron microscopy on cultured chicken fibroblasts, the protein was localized to focal adhesions in which it showed a distinct codistribution with the focal adhesion proteins vinculin, talin, and paxillin. Phosphoamino acid analysis showed that in cultured chicken heart fibroblasts, the protein contains phosphoserine, but no phosphothreonine or phosphotyrosine, and that the phosphorylation is not dependent on fibronectin. We propose this protein the name FAP52, for Focal Adhesion Protein of 52 kDa, and suggest that it forms part of the multimolecular complex constituting focal adhesion sites.

Highlights

Focal adhesions (FAs)1 are specialized membrane domains in cultured cells that mediate the attachment of cells to the growth substratum and extracellular matrix
The biochemical composition of FAs provides a large inventory of proteins, including structural proteins, such as cytoskeletal proteins vinculin, paxillin, and talin, integrins which provide the transmembrane linkage to the extracellular matrix, and several regulatory and signaling molecules such as proteases, protein kinases, and phosphatases [1, 2]
Our strategy was based on the fact that, despite their overall low degree of similarity, there are fairly well conserved regions in the N and C termini of the various Src-homology 3 (SH3) domains [6]

Summary

Introduction

Focal adhesions (FAs) are specialized membrane domains in cultured cells that mediate the attachment of cells to the growth substratum and extracellular matrix. They consist of pericellular and transmembrane structures connected to the actin-based cytoskeleton. From a wealth of structural, biochemical, and genetic information, it has become apparent that the protein-protein interactions within FAs are based on conserved protein modules These include, e.g. in the regulatory components of the FAs, the well known Src-homology 2 (SH2) and Src-homology 3 (SH3) domains that are important, e.g. in the substrate recognition of kinases and in the protein targeting, respectively [4]. Due to its subcellular localization and molecular mass, we propose it a name Focal Adhesion Protein of 52,000 daltons, FAP52

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