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Abl family kinases and Cbl cooperate with the Nck adaptor to modulate Xenopus development
C E Adler1, T Miyoshi-Akiyama, L M Aleman
1Laboratory of Molecular Medicine, Children's Hospital and Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Abstract:
We previously showed that overexpression of the Nck Src homology (SH) 2/SH3 adaptor in Xenopus embryos induced developmental defects including anterior truncation and mesoderm ventralization. Mutagenic analysis indicated that this was due to relocalization of endogenous proteins that bind the first two SH3 domains of Nck. We therefore screened a Xenopus expression library with Nck SH3 domains to identify Nck-interacting proteins, and evaluated candidate binding proteins for a potential role in Nck-induced anterior truncation/ventralization. Of 39 binding proteins analyzed, only the Abl-related kinase Arg and the Cbl proto-oncogene product bound preferentially to the first two SH3 domains in tandem compared with the individual domains, consistent with a role in the developmental phenotype. High level overexpression of c-Abl or Arg alone induced anterior truncation, as did lower levels of an activated form of Abl; Cbl alone had no effect. In a sensitized system where subthreshold amounts of a ventralizing Nck mutant were expressed, co-expression of the combination of Abl or Arg and Cbl at modest levels strongly potentiated anterior truncation, while Arg, Abl, or Cbl alone were without effect. These results suggest a role for both Cbl and Abl family kinases in patterning the Xenopus embryo.
Insights
Overexpression of Nck adaptor protein in Xenopus embryos caused developmental defects. Abl and Cbl kinases interact with Nck and are implicated in embryonic patterning.
Area of Science:
- Developmental biology
- Molecular cell biology
- Biochemistry
Background:
- Nck adaptor protein (Src homology 2/Src homology 3) overexpression in Xenopus embryos leads to anterior truncation and mesoderm ventralization.
- This phenotype is linked to the relocalization of endogenous proteins that bind to Nck's SH3 domains.
Purpose of the Study:
- To identify Nck-interacting proteins using Nck SH3 domains.
- To evaluate the role of identified binding proteins in Nck-induced developmental defects, specifically anterior truncation and ventralization.
Main Methods:
- Screening of a Xenopus expression library using Nck SH3 domains.
- Analysis of protein binding affinities to individual and tandem SH3 domains.
- Overexpression studies of candidate proteins (c-Abl, Arg, Cbl) in Xenopus embryos.
Main Results:
- Arg (Abl-related kinase) and Cbl proto-oncogene product preferentially bound to tandem Nck SH3 domains.
- Overexpression of c-Abl or Arg alone caused anterior truncation; Cbl alone had no effect.
- Co-expression of Abl or Arg with Cbl potentiated Nck mutant-induced anterior truncation.
Conclusions:
- Abl and Cbl family kinases play a role in Nck-mediated developmental patterning in Xenopus embryos.
- These findings suggest a functional interaction between Nck, Abl, and Cbl in embryonic development.