Growth Factor-Triggered De-Sialylation Controls Glycolipid-Lectin-Driven Endocytosis
In cell biology, the glycosylation modification of cell surface glycoproteins plays a crucial role in processes such as cell signaling, adhesion, and migration. How dynamic changes in glycosylation regulate intracellular transport and function, particularly the internalization of cell surface receptors through endocytosis, remains an incompletely understood puzzle. Epidermal growth factor (EGF) is an important growth factor that, by binding to the epidermal growth factor receptor (EGFR), triggers a series of intracellular signaling events that affect cell proliferation, migration, and survival. However, whether and how EGF regulates the glycosylation of cell surface glycoproteins to influence endocytosis has not been fully explored.
This study aims to investigate whether EGF triggers endocytosis by regulating the de-sialylation of cell surface glycoproteins and to reveal the molecular mechanisms underlying this process. De-sialylation refers to the removal of sialic acid from the glycan chains of glycoproteins, and the presence of sialic acid typically affects the binding of glycoproteins to lectins such as galectin-3 (Gal3). Gal3 is a widely expressed cell surface lectin that can trigger clathrin-independent endocytosis by recognizing de-sialylated glycoproteins. This study not only reveals how EGF regulates endocytosis through de-sialylation but also proposes a novel regulatory mechanism—the de-sialylation glycoswitch—providing new insights into the dynamic regulation of cell surface glycosylation.
Source of the Paper
This paper was co-authored by Ewan Macdonald, Alison Forrester, Cesar A. Valades-Cruz, and others from multiple research institutions, including the Institut Curie in France, the University of Copenhagen in Denmark, and the National Institutes of Health (NIH) in the United States. The paper was published in March 2025 in the journal Nature Cell Biology under the title “Growth factor-triggered de-sialylation controls glycolipid-lectin-driven endocytosis.”
Research Process and Results
1. EGF Triggers De-sialylation of Cell Surface Glycoproteins
The study first experimentally verified whether EGF could trigger the de-sialylation of cell surface glycoproteins. Using the MDA-MB-231 breast cancer cell line, researchers observed that EGF stimulation significantly increased the binding of Gal3 to the cell surface. This phenomenon was validated in multiple cell lines, including tongue squamous cell carcinoma cells and mouse embryonic fibroblasts. By treating cells with DANA, a sialidase inhibitor, researchers found that EGF-induced Gal3 binding depended on sialidase activity, indicating that EGF regulates Gal3 binding through de-sialylation.
2. Molecular Mechanism of De-sialylation
To uncover how EGF triggers de-sialylation, researchers used siRNA screening and CRISPR gene editing techniques to identify Neu1 and Neu3, two sialidases, as key players in this process. Neu1 and Neu3 are two sialidases located on the cell membrane, and their activity is enhanced in acidic environments. Further experiments showed that EGF activates the Na+/H+ exchanger NHE1, leading to acidification of the extracellular environment, which in turn activates Neu1 and Neu3 to trigger de-sialylation. This discovery reveals the molecular link between EGF signaling and de-sialylation.
3. De-sialylation Triggers Endocytosis
Next, researchers investigated whether de-sialylation triggers endocytosis. Using fluorescently labeled α3β1 integrin antibodies, they observed that EGF significantly increased the endocytosis of α3β1 integrin, a process dependent on Gal3 binding. By inhibiting Gal3, NHE1, or sialidase activity, EGF-induced endocytosis was significantly suppressed, indicating that de-sialylation triggers endocytosis through Gal3.
4. Relationship Between De-sialylation and Cell Migration
Finally, researchers explored the role of de-sialylation in cell migration. Using cell-derived matrices and inverted invasion assays, they found that EGF significantly promoted the migration of MDA-MB-231 cells, an effect dependent on Gal3 and sialidase activity. This suggests that de-sialylation not only regulates endocytosis but also plays an important role in cell migration.
Conclusions and Significance
This study proposes a novel regulatory mechanism—the de-sialylation glycoswitch—revealing how EGF regulates the endocytosis and function of cell surface glycoproteins through de-sialylation. This discovery not only deepens our understanding of the dynamic regulation of cell surface glycosylation but also provides new molecular mechanisms for tumor cell migration and invasion. Additionally, this study offers a theoretical basis for developing therapeutic strategies targeting the de-sialylation process, particularly in the field of cancer treatment.
Research Highlights
- Novel Regulatory Mechanism: This study is the first to propose the concept of the de-sialylation glycoswitch, revealing the molecular mechanism by which EGF regulates endocytosis through de-sialylation.
- Multi-level Experimental Validation: Using techniques such as siRNA screening, CRISPR gene editing, fluorescent labeling, and electron microscopy, researchers comprehensively validated the role of de-sialylation in endocytosis and cell migration at the molecular, cellular, and organismal levels.
- Potential Clinical Applications: This study provides new molecular mechanisms for tumor cell migration and invasion, offering a theoretical basis for developing therapeutic strategies targeting the de-sialylation process.
Other Valuable Information
The findings of this study are not only applicable to EGF signaling but may also extend to other growth factors and signaling pathways. For example, tumor necrosis factor (TNF) can also trigger endocytosis through a similar mechanism, suggesting that the de-sialylation glycoswitch may be a widely existing regulatory mechanism. Additionally, this study provides new insights into the role of cell surface glycosylation in immune regulation, neural signaling, and other processes.