Related Experiment Videos
Molecular cloning of a cDNA encoding a phosphoprotein, Efs, which contains a Src homology 3 domain and associates
1Department of Biochemistry, Sapporo Medical University School of Medicine, Japan.
Abstract:
Src homology 2 and 3 (SH2 and SH3) domains mediate protein-protein interactions in intracellular signaling by protein-tyrosine kinases (PTKs). We have isolated cDNA clones from mouse embryo cDNA expression library that encode a new signaling protein which we call Efs (Embryonal Fyn-associated Substrate). The deduced amino acid sequence of 560 residues in length revealed one SH3 domain at its amino-terminal region, two proline-rich motifs with the consensus sequences of binding to Src-family SH3s, and a cluster of YXXP motifs that are possibly tyrosine-phosphorylated to serve as ligands binding to SH2 domains. Structure and alignment of these characteristics sequences are homologous to those of p130Cas, but Efs and p130Cas are different proteins. Expression of the Efs gene was higher in placenta, embryo and brain than in other adult tissues. Transfection of COS-7 cells with a plasmid encoding an epitope-tagged Efs resulted in the expression of a 83 kDa protein. The epitope-tagged Efs was hyperphosphorylated when cotransfected with a vector expressing Fyn. In an in vitro kinase assay with the PCC4 cell lysate, Efs became phosphorylated on tyrosine residues and coprecipitated with p59fyn and p62yes; the result suggests that Efs is a physiological substrate of these PTKs.
Insights
Researchers identified a novel signaling protein, Embryonal Fyn-associated Substrate (Efs), involved in intracellular communication. Efs acts as a substrate for protein-tyrosine kinases, suggesting a role in cellular signaling pathways.
Area of Science:
- Molecular Biology
- Cell Signaling
- Protein Biochemistry
Background:
- Protein-tyrosine kinases (PTKs) utilize Src homology 2 (SH2) and 3 (SH3) domains for intracellular signaling.
- Understanding novel signaling proteins is crucial for elucidating complex cellular communication networks.
Purpose of the Study:
- To isolate and characterize a novel signaling protein involved in PTK-mediated signaling pathways.
- To investigate the functional domains and potential interactions of the newly identified protein.
Main Methods:
- cDNA library screening using mouse embryo cDNA.
- Sequence analysis to identify functional domains (SH3, proline-rich motifs, YXXP motifs).
- Gene expression analysis in various tissues.
- Protein expression and phosphorylation studies in COS-7 cells via transfection.
- In vitro kinase assays and co-precipitation experiments.
Main Results:
- Isolation of cDNA encoding a new signaling protein, Efs (Embryonal Fyn-associated Substrate).
- Efs possesses an SH3 domain, proline-rich motifs for SH3 binding, and YXXP motifs for SH2 binding, homologous to p130Cas but distinct.
- Efs gene expression is highest in placenta, embryo, and brain.
- Efs is an 83 kDa protein, hyperphosphorylated by Fyn, and acts as a substrate for PTKs like p59fyn and p62yes.
Conclusions:
- Efs is a novel signaling protein interacting with Src-family kinases.
- Efs is a physiological substrate for PTKs, indicating its role in intracellular signaling.
- The structural and functional characteristics of Efs suggest its involvement in embryonic development and neuronal signaling.