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Activation of EphA2 kinase suppresses integrin function and causes focal-adhesion-kinase dephosphorylation
1Rammelkamp Center for Research, MetroHealth Campus, Case Western Reserve University School of Medicine, 2500 MetroHealth Drive, Cleveland, Ohio 44109, USA.
Abstract:
Interactions between receptor tyrosine kinases of the Eph family and their ligands, ephrins, are implicated in establishment of organ boundaries and repulsive guidance of cell migration during development, but the mechanisms by which this is achieved are unclear. Here we show that activation of endogenous EphA2 kinase induces an inactive conformation of integrins and inhibits cell spreading, migration and integrin-mediated adhesion. Moreover, EphA2 is constitutively associated with focal-adhesion kinase (FAK) in resting cells. Within one minute after stimulation of EphA2 with its ligand, ephrin-A1, the protein tyrosine phosphatase SHP2 is recruited to EphA2; this is followed by dephosphorylation of FAK and paxillin, and dissociation of the FAK-EphA2 complex. We conclude that Eph kinases mediate some of their functions by negatively regulating integrins and FAK.
Insights
Eph receptor tyrosine kinases (RTKs) regulate cell migration and organ development. This study reveals EphA2 activation inhibits integrin function and cell adhesion by dephosphorylating focal-adhesion kinase (FAK).
Area of Science:
- Cell Biology
- Developmental Biology
- Molecular Biology
Background:
- Eph receptor tyrosine kinases (RTKs) and ephrin ligands are crucial for cell guidance and organ boundary formation during development.
- The precise molecular mechanisms by which Eph-ephrin signaling influences cell behavior remain incompletely understood.
Purpose of the Study:
- To elucidate the role of EphA2 kinase activation in regulating integrin function and cell adhesion.
- To investigate the molecular interactions and signaling events downstream of EphA2 activation.
Main Methods:
- Activation of endogenous EphA2 kinase using its ligand, ephrin-A1.
- Analysis of integrin conformation, cell spreading, migration, and adhesion.
- Co-immunoprecipitation assays to study protein-protein interactions between EphA2, focal-adhesion kinase (FAK), and SHP2.
- Western blotting to assess protein dephosphorylation.
Main Results:
- EphA2 kinase activation leads to an inactive integrin conformation, inhibiting cell spreading, migration, and adhesion.
- EphA2 constitutively associates with FAK in resting cells.
- Upon ephrin-A1 stimulation, SHP2 phosphatase is recruited to EphA2, causing dephosphorylation of FAK and paxillin, and dissociation of the EphA2-FAK complex.
Conclusions:
- Eph kinases, specifically EphA2, negatively regulate integrin activity and focal-adhesion kinase (FAK) signaling.
- This signaling pathway provides a mechanism for Eph-ephrin mediated control over cell adhesion and migration during development.