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Isolation and characterization of cortactin isoforms and a novel cortactin‐binding protein, CBP90
Author(s) -
Ohoka Yoshiharu,
Takai Yoshimi
Publication year - 1998
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1046/j.1365-2443.1998.00216.x
Subject(s) - cortactin , biology , sh3 domain , microbiology and biotechnology , gene isoform , complementary dna , peptide sequence , biochemistry , c terminus , actin , proto oncogene tyrosine protein kinase src , amino acid , gene , cytoskeleton , signal transduction , cell
Background Cortactin is a major phosphotyrosyl protein in pp60 v–src ‐transformed chicken embryo cells. Cortactin binds to actin filament (F‐actin) through a unique region which consists of six tandem 37 amino acid repeats, named cortactin repeats. Furthermore cortactin has one src homology 3 (SH3) domain. Results In this study we have isolated two new isoforms of cortactin from the rat brain using a polymerase chain reaction (PCR) method, and have named the original cortactin as cortactin‐A and the newly isolated forms as cortactin‐B and ‐C. Cortactin‐A, ‐B and ‐C had six, five, and four cortactin repeats, respectively. All the isoforms were able to bind to F‐actin, but only cortactin‐A demonstrated an F‐actin‐crosslinking activity. In addition, cortactin‐A was able to bind along the side of F‐actin. Next, using a blot overlay assay with glutathione S‐ transferase (GST)‐cortactin‐A, we identified a cortactin‐A‐binding protein with an M r of ≈90 kDa in rat brain and named it CBP90 (cortactin‐binding protein with an M r of ≈90 KDa). CBP90 was purified from rat brain and its cDNA was cloned from a rat brain cDNA library. The deduced amino acid sequence of CBP90 had no significant similarity to any other protein, but it had a proline‐rich domain at the C‐terminal region. CBP90 was able to bind to all the cortactin isoforms. A deletion mutant analysis of cortactin‐A and CBP90 revealed that the SH3 domain of cortactin‐A was able to bind to the proline‐rich region of CBP90. A Western blot analysis with an anti‐CBP90 antibody indicated that, among the rat tissues examined, CBP90 was exclusively expressed in brain. Furthermore, its subcellular distribution and developmental expression patterns were similar to those of cortactin. Conclusion These results suggest that cortactin interacts with CBP90 and plays a role in regulation of the actin cytoskeleton in brain.