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The SH2/SH3 adaptor Grb4 transduces B-ephrin reverse signals
1Center for Developmental Biology and Kent Waldrep Foundation Center for Basic Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas 75390-9133, USA.
Nature
|September 15, 2001
Summary
Ephrin reverse signaling activates Grb4, a protein adapter, leading to cytoskeletal changes in cells. This discovery reveals a new pathway for cell-cell recognition during development.
Area of Science:
- Cell Biology
- Molecular Biology
- Neuroscience
Background:
- Ephrin and Eph receptor tyrosine kinase signaling mediates cell-cell recognition.
- Reverse signaling in ephrin-expressing cells involves tyrosine phosphorylation.
- The proteins interacting with phosphorylated ephrins and cellular responses to reverse signaling were previously undefined.
Purpose of the Study:
- To identify proteins that bind to activated B-ephrins.
- To characterize the cellular responses to B-ephrin reverse signaling.
- To elucidate the biochemical pathway linking ephrin signaling to cytoskeletal regulation.
Main Methods:
- Co-immunoprecipitation to identify binding partners.
- Dominant-negative inhibition to assess Grb4 function.
- Analysis of cellular morphology and cytoskeletal components (focal adhesions, F-actin stress fibers).
Main Results:
- Grb4 binds to the cytoplasmic domain of B-ephrins in a phosphotyrosine-dependent manner.
- B-ephrin reverse signaling increases FAK activity, paxillin redistribution, focal adhesion loss, cell rounding, and stress fiber disassembly.
- Grb4 SH3 domains bind cytoskeletal regulators like CAP/ponsin and Abi-1.
Conclusions:
- Grb4 acts as a key adaptor protein in B-ephrin reverse signaling.
- Ephrin reverse signaling directly impacts cell adhesion and cytoskeletal organization.
- A novel biochemical pathway is established, connecting Eph-ephrin signaling to cytoskeletal regulators via Grb4.
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