Regulation of Raf-1 by direct feedback phosphorylation

Michele K. Dougherty, Jürgen Müller, Daniel A. Ritt, Ming Zhou, Xiao Zhen Zhou, Terry D. Copeland, Thomas P. Conrads, Timothy D. Veenstra, Kun Ping Lu, Deborah K. Morrison*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

495 Scopus citations


The Raf-1 kinase is an important signaling molecule, functioning in the Ras pathway to transmit mitogenic, differentiative, and oncogenic signals to the downstream kinases MEK and ERK. Because of its integral role in cell signaling, Raf-1 activity must be precisely controlled. Previous studies have shown that phosphorylation is required for Raf-1 activation, and here, we identify six phosphorylation sites that contribute to the downregulation of Raf-1 after mitogen stimulation. Five of the identified sites are proline-directed targets of activated ERK, and phosphorylation of all six sites requires MEK signaling, indicating a negative feedback mechanism. Hyperphosphorylation of these six sites inhibits the Ras/Raf-1 interaction and desensitizes Raf-1 to additional stimuli. The hyperphosphorylated/desensitized Raf-1 is subsequently dephosphorylated and returned to a signaling-competent state through interactions with the protein phosphatase PP2A and the prolyl isomerase Pin1. These findings elucidate a critical Raf-1 regulatory mechanism that contributes to the sensitive, temporal modulation of Ras signaling.

Original languageEnglish
Pages (from-to)215-224
Number of pages10
JournalMolecular Cell
Issue number2
StatePublished - 21 Jan 2005
Externally publishedYes


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