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08:05
Assaying Protein Kinase Activity with Radiolabeled ATP
Published on: May 26, 2017
Phosphorylation regulates KSR1 stability, ERK activation, and cell proliferation
Gina L Razidlo1, Robert L Kortum, Jamie L Haferbier
1Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696, USA.
The Journal of Biological Chemistry
|September 17, 2004
Summary
Phosphorylation of Kinase Suppressor of Ras 1 (KSR1) regulates its stability and localization, controlling cell proliferation. Mutating specific phosphorylation sites enhances ERK signaling and cell cycle progression, regardless of growth factor type.
Area of Science:
- Molecular Biology
- Cell Signaling
- Cancer Research
Background:
- Kinase Suppressor of Ras (KSR) acts as a molecular scaffold in the Raf/MEK/ERK pathway, crucial for regulating ERK signaling.
- Phosphorylation of KSR1, particularly at Ser(392), dictates its localization and impacts ERK activation.
- Understanding KSR1 phosphorylation is key to deciphering growth factor-specific signaling and cell proliferation control.
Purpose of the Study:
- To investigate the role of KSR1 phosphorylation at Ser(392) and Thr(274) in regulating ERK activation and cell proliferation.
- To determine if KSR1 phosphorylation contributes to signaling specificity within the Raf/MEK/ERK cascade in response to distinct growth factors.
- To elucidate the impact of KSR1 phosphorylation status on KSR1 stability and its downstream effects on cell cycle progression.
Main Methods:
- Utilized site-directed mutagenesis to create KSR1 variants with mutations at Ser(392) and Thr(274) (KSR1.TVSA).
- Assessed ERK activation, cell cycle progression (S-phase entry), and KSR1 stability in response to platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) stimulation.
- Compared proliferation rates and cell density of KSR1(-/-) mouse embryo fibroblasts expressing either wild-type KSR1 or KSR1.TVSA.
Main Results:
- Mutation of Ser(392) and Thr(274) (KSR1.TVSA) led to sustained ERK activation and promoted cell cycle progression with both PDGF and EGF.
- KSR1(-/-) MEFs expressing KSR1.TVSA exhibited a two-fold increase in proliferation and reached higher cell densities compared to those with wild-type KSR1.
- The KSR1.TVSA mutant demonstrated enhanced stability relative to wild-type KSR1.
Conclusions:
- KSR1 phosphorylation and stability are critical determinants of growth factor-specific signaling outcomes.
- Modulating KSR1 phosphorylation can override growth factor-induced signaling specificity, promoting robust cell proliferation.
- These findings highlight KSR1 phosphorylation as a key regulatory mechanism controlling cell growth and division.
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