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Updated: Jan 11, 2026
Studying TGF-β Signaling and TGF-β-induced Epithelial-to-mesenchymal Transition in Breast Cancer and Normal Cells
Published on: October 27, 2020
MARCH2-mediated Lys63-linked polyubiquitination promotes metastasis by modulating the catalytic activity of TGF-β
Kun Tae1, Sang Woo Cho1, Seonjeong Lee2
1Department of Biological Sciences, Sungkyunkwan University, Suwon, Republic of Korea.
Abstract:
The TGF-β signaling pathway is initiated when the type II receptor phosphorylates the type I receptor (ALK5) upon TGF-β binding. While E3 ubiquitin ligases regulate TGF-β receptor degradation, their role in modulating receptor catalytic activity via ubiquitination remains largely unexplored. Here, we demonstrate that the E3 ubiquitin ligase MARCH2 enhances ALK5 catalytic activity by conjugating K63-linked ubiquitin chains to lysines 342/343 (K342/343), primarily at endosomes following TGF-β-induced endocytosis. Mutations of ALK5 at K342/343 (K342/343R) abolish its catalytic activity for SMAD2 phosphorylation, leading to impaired TGF-β responses and reduced cell migration in A549 cells. In a mouse model, expression of the ALK5 K342/343 R mutant significantly decreases lung metastasis compared to wild-type ALK5. TCGA analysis further revealed a strong positive correlation between MARCH2 expression and TGF-β target gene expression. Collectively, these findings establish ALK5 ubiquitination at K342/343 by MARCH2 as a crucial regulatory mechanism for ALK5 catalytic activity, TGF-β signaling, and metastasis.
Insights
The E3 ubiquitin ligase MARCH2 enhances TGF-β receptor ALK5 activity by ubiquitination, impacting cell migration and metastasis. This discovery reveals a new regulatory mechanism in TGF-β signaling.
Area of Science:
- Molecular Biology
- Cell Signaling
- Cancer Research
Background:
- The transforming growth factor-beta (TGF-β) signaling pathway is crucial in cellular processes.
- E3 ubiquitin ligases are known to regulate receptor degradation, but their role in receptor catalytic activity is less understood.
Purpose of the Study:
- To investigate the role of E3 ubiquitin ligase MARCH2 in modulating the catalytic activity of the TGF-β type I receptor (ALK5).
- To explore the impact of ALK5 ubiquitination on TGF-β signaling and downstream cellular functions, including metastasis.
Main Methods:
- Investigated the interaction between MARCH2 and ALK5 using biochemical assays.
- Utilized site-directed mutagenesis to examine the role of specific lysine residues (K342/343) in ALK5 ubiquitination and activity.
- Assessed TGF-β signaling, cell migration, and lung metastasis in cellular and mouse models.
- Analyzed The Cancer Genome Atlas (TCGA) data for correlations between MARCH2 expression and TGF-β target genes.
Main Results:
- MARCH2 enhances ALK5 catalytic activity by conjugating K63-linked ubiquitin chains to ALK5 at lysines 342/343.
- Mutating ALK5 at K342/343 abolished its catalytic activity, impairing SMAD2 phosphorylation and TGF-β responses.
- ALK5 K342/343R mutant significantly reduced lung metastasis in a mouse model.
- MARCH2 expression positively correlated with TGF-β target gene expression in TCGA data.
Conclusions:
- ALK5 ubiquitination at K342/343 by MARCH2 is a key regulatory mechanism for ALK5 catalytic activity.
- This ubiquitination event is critical for TGF-β signaling, cell migration, and metastasis.
- MARCH2-mediated ALK5 ubiquitination represents a potential therapeutic target for TGF-β-related diseases and cancer.
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