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KSR modulates signal propagation within the MAPK cascade
M Therrien1, N R Michaud, G M Rubin
1Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California at Berkeley, 94720-3200, USA.
Genes & Development
|November 1, 1996
Summary
Murine KSR1 (mKSR1) protein interacts with Ras to promote cell growth and division by activating MEK and MAPK signaling pathways. Its distinct domains regulate this Ras-dependent signaling complex.
Area of Science:
- Molecular Biology
- Cell Signaling
- Ras/MAPK Pathway
Background:
- Kinase suppressor of Ras (KSR) is a key regulator in Ras-dependent signaling pathways.
- Understanding KSR's role is crucial for deciphering cellular growth and transformation mechanisms.
Purpose of the Study:
- To investigate the function of murine KSR1 (mKSR1) in Ras-mediated signaling.
- To elucidate the mechanism by which mKSR1 modulates MEK and MAPK activation.
- To compare the functional domains of mKSR1 with Raf-1.
Main Methods:
- Xenopus oocyte maturation assays.
- Cellular transformation assays.
- Analysis of protein-protein interactions at the plasma membrane.
- Domain-specific functional analysis of mKSR1 and Raf-1.
Main Results:
- mKSR1 cooperates with activated Ras to promote oocyte maturation and cellular transformation.
- mKSR1 accelerates the activation of mitogen and extracellular regulated kinase (MEK) and mitogen-activated protein kinase (MAPK).
- mKSR1 forms a membrane-bound complex with Raf-1 in a Ras-dependent manner.
- The amino terminus of mKSR1 cooperates with Ras, while the kinase domain inhibits signaling.
Conclusions:
- mKSR1 is an integral component of the MAPK signaling module.
- mKSR1 employs a novel mechanism to regulate signal propagation between Raf-1, MEK1, and MAPK.
- The functional separation of mKSR1 domains uncouples its normal regulation as a positive effector of Ras signaling.