Limits...
PAK1 phosphorylation of MEK1 regulates fibronectin-stimulated MAPK activation.

Slack-Davis JK, Eblen ST, Zecevic M, Boerner SA, Tarcsafalvi A, Diaz HB, Marshall MS, Weber MJ, Parsons JT, Catling AD - J. Cell Biol. (2003)

Bottom Line: Activation of the Ras-MAPK signal transduction pathway is necessary for biological responses both to growth factors and ECM.Here, we provide evidence that phosphorylation of S298 of MAPK kinase 1 (MEK1) by p21-activated kinase (PAK) is a site of convergence for integrin and growth factor signaling.We propose that FAK/Src-dependent, PAK1-mediated phosphorylation of MEK1 on S298 is central to the organization and localization of active Raf-MEK1-MAPK signaling complexes, and that formation of such complexes contributes to the adhesion dependence of growth factor signaling to MAPK.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Virginia Health System, Charlottesville, VA 22908, USA.

ABSTRACT
Activation of the Ras-MAPK signal transduction pathway is necessary for biological responses both to growth factors and ECM. Here, we provide evidence that phosphorylation of S298 of MAPK kinase 1 (MEK1) by p21-activated kinase (PAK) is a site of convergence for integrin and growth factor signaling. We find that adhesion to fibronectin induces PAK1-dependent phosphorylation of MEK1 on S298 and that this phosphorylation is necessary for efficient activation of MEK1 and subsequent MAPK activation. The rapid and efficient activation of MEK and phosphorylation on S298 induced by cell adhesion to fibronectin is influenced by FAK and Src signaling and is paralleled by localization of phospho-S298 MEK1 and phospho-MAPK staining in peripheral membrane-proximal adhesion structures. We propose that FAK/Src-dependent, PAK1-mediated phosphorylation of MEK1 on S298 is central to the organization and localization of active Raf-MEK1-MAPK signaling complexes, and that formation of such complexes contributes to the adhesion dependence of growth factor signaling to MAPK.

Show MeSH

Related in: MedlinePlus

Phosphorylation of MEK1 on S298 regulates MEK1 activation. REF52 cells were transiently transfected with HA-MEK1, HA-MEK1 T292A, HA-MEK1 S298A, or HA-MEK1 T292A/S298A. Cells were suspended for 90 min (S) and plated on FN for 20 min (FN). Anti-HA immunoprecipitates were formed and blotted with anti-p-S218/S222MEK1 (top), anti-pS298MEK1 (middle), or anti-HA antiserum (bottom).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172784&req=5

fig5: Phosphorylation of MEK1 on S298 regulates MEK1 activation. REF52 cells were transiently transfected with HA-MEK1, HA-MEK1 T292A, HA-MEK1 S298A, or HA-MEK1 T292A/S298A. Cells were suspended for 90 min (S) and plated on FN for 20 min (FN). Anti-HA immunoprecipitates were formed and blotted with anti-p-S218/S222MEK1 (top), anti-pS298MEK1 (middle), or anti-HA antiserum (bottom).

Mentions: MEK1 containing an S298A mutation was reported to bind less efficiently to Raf than wild-type MEK1 indicating that MEK1 S298 phosphorylation regulates the interaction of MEK1 with its upstream activator (Frost et al., 1997). To examine the requirement for S298 phosphorylation on FN-stimulated MEK1 activation, cells expressing HA-tagged MEK1 variants containing T292A, S298A, or T292A/S298A mutations were placed in suspension or plated on FN for 20 min. The MEK1 variants were immunoprecipitated and blotted for p-S218/S222 MEK as an indicator of MEK activation. Phosphorylation of S218/S222 was stimulated by FN in cells expressing both wild-type MEK1 and MEK1 T292A, but not in cells expressing MEK1 S298A or MEK1 T292A/S298A (Fig. 5). Thus, MEK1 S298 is necessary for efficient activation of MEK1 during adhesion.


PAK1 phosphorylation of MEK1 regulates fibronectin-stimulated MAPK activation.

Slack-Davis JK, Eblen ST, Zecevic M, Boerner SA, Tarcsafalvi A, Diaz HB, Marshall MS, Weber MJ, Parsons JT, Catling AD - J. Cell Biol. (2003)

Phosphorylation of MEK1 on S298 regulates MEK1 activation. REF52 cells were transiently transfected with HA-MEK1, HA-MEK1 T292A, HA-MEK1 S298A, or HA-MEK1 T292A/S298A. Cells were suspended for 90 min (S) and plated on FN for 20 min (FN). Anti-HA immunoprecipitates were formed and blotted with anti-p-S218/S222MEK1 (top), anti-pS298MEK1 (middle), or anti-HA antiserum (bottom).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172784&req=5

fig5: Phosphorylation of MEK1 on S298 regulates MEK1 activation. REF52 cells were transiently transfected with HA-MEK1, HA-MEK1 T292A, HA-MEK1 S298A, or HA-MEK1 T292A/S298A. Cells were suspended for 90 min (S) and plated on FN for 20 min (FN). Anti-HA immunoprecipitates were formed and blotted with anti-p-S218/S222MEK1 (top), anti-pS298MEK1 (middle), or anti-HA antiserum (bottom).
Mentions: MEK1 containing an S298A mutation was reported to bind less efficiently to Raf than wild-type MEK1 indicating that MEK1 S298 phosphorylation regulates the interaction of MEK1 with its upstream activator (Frost et al., 1997). To examine the requirement for S298 phosphorylation on FN-stimulated MEK1 activation, cells expressing HA-tagged MEK1 variants containing T292A, S298A, or T292A/S298A mutations were placed in suspension or plated on FN for 20 min. The MEK1 variants were immunoprecipitated and blotted for p-S218/S222 MEK as an indicator of MEK activation. Phosphorylation of S218/S222 was stimulated by FN in cells expressing both wild-type MEK1 and MEK1 T292A, but not in cells expressing MEK1 S298A or MEK1 T292A/S298A (Fig. 5). Thus, MEK1 S298 is necessary for efficient activation of MEK1 during adhesion.

Bottom Line: Activation of the Ras-MAPK signal transduction pathway is necessary for biological responses both to growth factors and ECM.Here, we provide evidence that phosphorylation of S298 of MAPK kinase 1 (MEK1) by p21-activated kinase (PAK) is a site of convergence for integrin and growth factor signaling.We propose that FAK/Src-dependent, PAK1-mediated phosphorylation of MEK1 on S298 is central to the organization and localization of active Raf-MEK1-MAPK signaling complexes, and that formation of such complexes contributes to the adhesion dependence of growth factor signaling to MAPK.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Virginia Health System, Charlottesville, VA 22908, USA.

ABSTRACT
Activation of the Ras-MAPK signal transduction pathway is necessary for biological responses both to growth factors and ECM. Here, we provide evidence that phosphorylation of S298 of MAPK kinase 1 (MEK1) by p21-activated kinase (PAK) is a site of convergence for integrin and growth factor signaling. We find that adhesion to fibronectin induces PAK1-dependent phosphorylation of MEK1 on S298 and that this phosphorylation is necessary for efficient activation of MEK1 and subsequent MAPK activation. The rapid and efficient activation of MEK and phosphorylation on S298 induced by cell adhesion to fibronectin is influenced by FAK and Src signaling and is paralleled by localization of phospho-S298 MEK1 and phospho-MAPK staining in peripheral membrane-proximal adhesion structures. We propose that FAK/Src-dependent, PAK1-mediated phosphorylation of MEK1 on S298 is central to the organization and localization of active Raf-MEK1-MAPK signaling complexes, and that formation of such complexes contributes to the adhesion dependence of growth factor signaling to MAPK.

Show MeSH
Related in: MedlinePlus