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Updated: Feb 5, 2026
Monitoring Kinase and Phosphatase Activities Through the Cell Cycle by Ratiometric FRET
Published on: January 27, 2012
Activation loop phosphorylation of ERK3 is important for its kinase activity and ability to promote lung cancer cell
Lobna Elkhadragy1, Hadel Alsaran1, Marion Morel1
1From the Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio 45435.
Abstract:
ERK3 is an atypical mitogen-activated protein kinase (MAPK) that has recently gained interest for its role in promoting cancer cell migration and invasion. However, the molecular regulation of ERK3 functions in cancer cells is largely unknown. ERK3 has a single phospho-acceptor site (Ser189) in its activation motif rather than the TXY conserved in conventional MAPKs such as ERK1/2. Although dual phosphorylation of the TXY motif is known to be critical for the activation of conventional MAPKs, the role of Ser189 phosphorylation in ERK3 activity and its function in cancer cells remain elusive. In this study, we revealed that activation loop phosphorylation is important for ERK3 in promoting cancer cell invasiveness, as the S189A mutation greatly decreased the ability of ERK3 to promote migration and invasion of lung cancer cells. Interestingly, a catalytically inactive ERK3 mutant was still capable of increasing migration and invasion, although to a lesser extent compared with WT ERK3, suggesting that ERK3 promotes cancer cell invasiveness by both kinase-dependent and kinase-independent mechanisms. To elucidate how the S189A mutation reduces the invasiveness-promoting ability of ERK3, we tested its effect on the kinase activity of ERK3 toward steroid receptor coactivator 3 (SRC3), a recently identified substrate of ERK3 critical for cancer cell invasiveness. Compared with ERK3, ERK3-S189A exhibited a dramatic decrease in kinase activity toward SRC3 and a concomitantly reduced ability to stimulate matrix metalloproteinase expression. Taken together, our study unravels the importance of Ser189 phosphorylation for intramolecular regulation of ERK3 kinase activity and invasiveness-promoting ability in lung cancer cells.
Insights
Phosphorylation of ERK3 at Serine 189 is crucial for its kinase activity and promotes lung cancer cell invasion. This finding reveals novel regulatory mechanisms for ERK3 in cancer progression.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Signaling
Background:
- Extracellular signal-regulated kinase 3 (ERK3) is an atypical mitogen-activated protein kinase (MAPK) implicated in cancer cell migration and invasion.
- The precise molecular mechanisms regulating ERK3 activity in cancer remain largely uncharacterized.
- Unlike conventional MAPKs, ERK3 possesses a unique activation motif with a single phospho-acceptor site (Serine 189).
Purpose of the Study:
- To investigate the role of Serine 189 phosphorylation in ERK3's kinase activity and its contribution to cancer cell invasiveness.
- To elucidate the mechanisms by which ERK3 promotes migration and invasion in lung cancer cells.
Main Methods:
- Utilized site-directed mutagenesis to create an ERK3 Serine 189 to Alanine (S189A) mutant.
- Assessed the impact of the S189A mutation on ERK3-mediated promotion of lung cancer cell migration and invasion.
- Evaluated the kinase activity of wild-type (WT) ERK3 and the S189A mutant towards steroid receptor coactivator 3 (SRC3).
- Measured the expression of matrix metalloproteinases (MMPs) in response to ERK3 activity.
Main Results:
- The S189A mutation significantly impaired ERK3's ability to promote lung cancer cell migration and invasion.
- A catalytically inactive ERK3 mutant retained partial ability to enhance migration and invasion, suggesting both kinase-dependent and independent roles.
- ERK3-S189A displayed markedly reduced kinase activity towards SRC3 compared to WT ERK3.
- Reduced SRC3 phosphorylation correlated with diminished stimulation of matrix metalloproteinase expression.
Conclusions:
- Activation loop phosphorylation at Serine 189 is critical for the intramolecular regulation of ERK3 kinase activity.
- ERK3 promotes lung cancer cell invasiveness through both kinase-dependent (e.g., SRC3 phosphorylation) and kinase-independent mechanisms.
- Targeting Serine 189 phosphorylation represents a potential strategy for inhibiting ERK3-driven cancer progression.
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