Phosphorylation of Rap1 by cAMP-dependent protein kinase (PKA) creates a binding site for KSR to sustain ERK activation by cAMP

Maho Takahashi, Yanping Li, Tara J. Dillon, Philip Stork

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Cyclic adenosine monophosphate (cAMP) is an important mediator of hormonal stimulation of cell growth and differentiation through its activation of the extracellular signal-regulated kinase (ERK) cascade. Two small G proteins, Ras and Rap1 have been proposed to mediate this activation. Using HEK293 cells as a model system, we have recently shown that both Ras and Rap1 are required for cAMP signaling to ERKs. However, cAMP-dependent Ras signaling to ERKs is transient and rapidly terminated by PKA phosphorylation of the Raf isoforms C-Raf and B-Raf. In contrast, cAMP-dependent Rap1 signaling to ERKs and Rap1 is potentiated by PKA. We show that this is due to sustained binding of B-Raf to Rap1. One of the targets of PKA is Rap1 itself, directly phosphorylating Rap1a on serine 180 and Rap1b on serine 179. We show that these phosphorylations create potential binding sites for the adaptor protein 14-3-3 that links Rap1 to the scaffold protein KSR. These results suggest that Rap1 activation of ERKs requiresPKAphosphorylation and KSR binding. Because KSR and B-Raf exist as heterodimers within the cell, this binding also brings B-Raf to Rap1, allowing Rap1 to couple to ERKs through B-Raf binding to Rap1 independently of its Ras-binding domain.

Original languageEnglish (US)
Pages (from-to)1449-1461
Number of pages13
JournalJournal of Biological Chemistry
Volume292
Issue number4
DOIs
StatePublished - Jan 27 2017

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Phosphorylation
Extracellular Signal-Regulated MAP Kinases
Cyclic AMP-Dependent Protein Kinases
Cyclic AMP
Chemical activation
Binding Sites
Protein Kinases
Serine
14-3-3 Proteins
Monomeric GTP-Binding Proteins
HEK293 Cells
Cell growth
Scaffolds
Cell Differentiation
Protein Isoforms
Growth
Proteins

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Phosphorylation of Rap1 by cAMP-dependent protein kinase (PKA) creates a binding site for KSR to sustain ERK activation by cAMP. / Takahashi, Maho; Li, Yanping; Dillon, Tara J.; Stork, Philip.

In: Journal of Biological Chemistry, Vol. 292, No. 4, 27.01.2017, p. 1449-1461.

Research output: Contribution to journalArticle

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