TY - JOUR
T1 - Regulation of Raf-1 by direct feedback phosphorylation
AU - Dougherty, Michele K.
AU - Müller, Jürgen
AU - Ritt, Daniel A.
AU - Zhou, Ming
AU - Zhou, Xiao Zhen
AU - Copeland, Terry D.
AU - Conrads, Thomas P.
AU - Veenstra, Timothy D.
AU - Lu, Kun Ping
AU - Morrison, Deborah K.
N1 - Funding Information:
We thank Tad Guszczynski for technical assistance and members of the Laboratory of Protein Dynamics and Cell Signaling for helpful discussions. K.P.L. is a Pew Scholar, a Leukemia and a Lymphoma Society Scholar, and a consultant to Pintex. This research was supported by funds from Department of Health and Human Services/National Institutes of Health/National Cancer Institute to D.K.M. and by National Institutes of Health grant RO1GM58556 to K.P.L.
PY - 2005/1/21
Y1 - 2005/1/21
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=19944430124&partnerID=8YFLogxK
U2 - 10.1016/j.molcel.2004.11.055
DO - 10.1016/j.molcel.2004.11.055
M3 - Article
C2 - 15664191
AN - SCOPUS:19944430124
SN - 1097-2765
VL - 17
SP - 215
EP - 224
JO - Molecular Cell
JF - Molecular Cell
IS - 2
ER -