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Thrombomodulin-mediated cell adhesion: involvement of its lectin-like domain
Huey-Chun Huang1, Guey-Yueh Shi, Shinn-Jong Jiang
1Department of Biochemistry, College of Medicine, National Cheng Kung University, Tainan, Taiwan 701, Republic of China.
Abstract:
Thrombomodulin (TM) is an integral membrane glycoprotein that is a potent anticoagulant factor. TM may also possess functions distinct from its anticoagulant activity. Here the influence of TM on cell adhesion was studied in TM-negative melanoma A2058 cells transfected with green fluorescent protein-tagged TM (TMG) or lectin domain-deleted TM (TMG(DeltaL)). Confocal microscopy demonstrated that both TMG and TMG(DeltaL) were distributed in the plasma membrane. TMG-expressed cells grew as closely clustered colonies, with TM localized prominently in the intercellular boundaries. TMG(DeltaL)-expressed cells grew singly. Overexpression of TMG, but not TMG(DeltaL), decreased monolayer permeability in vitro and tumor growth in vivo. The cell-to-cell adhesion in TMG-expressed cells was Ca2+-dependent and was inhibited by monoclonal antibody against the lectin-like domain of TM. The effects of TM-mediated cell adhesion were abolished by the addition of mannose, chondroitin sulfate A, or chondroitin sulfate C. In addition, anti-lectin-like domain antibody disrupted the close clustering of the endogenous TM-expressed keratinocyte HaCaT cell line derived from normal human epidermis. Double-labeling immunofluorescence staining revealed similar distributions of TM and actin filament in the cortex region of the TMG-expressed cells. Thus, TM can function as a Ca2+-dependent cell-to-cell adhesion molecule. Binding of specific carbohydrates to the lectin-like domain is essential for this specific function.
Insights
Thrombomodulin (TM) acts as a calcium-dependent cell adhesion molecule, promoting cell-to-cell binding. Its lectin-like domain is crucial for this function, influencing cell growth and tissue integrity.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Thrombomodulin (TM) is a membrane glycoprotein known for its anticoagulant properties.
- TM may have additional functions beyond anticoagulation.
- Investigating TM's role in cell adhesion is important for understanding its broader biological significance.
Purpose of the Study:
- To investigate the influence of Thrombomodulin (TM) on cell adhesion.
- To determine the role of TM's lectin-like domain in cell-to-cell interactions.
- To explore TM's impact on cell growth, monolayer permeability, and tumor development.
Main Methods:
- Transfection of TM-negative melanoma cells with TM variants (TMG and TMG(DeltaL)).
- Confocal microscopy to visualize TM distribution.
- In vitro assays for monolayer permeability and cell adhesion.
- In vivo studies of tumor growth.
- Inhibition studies using antibodies and specific carbohydrates.
Main Results:
- TM expression promoted Ca2+-dependent cell-to-cell adhesion and colony formation.
- TM localized to intercellular boundaries, influencing cell clustering.
- TM expression reduced monolayer permeability and in vivo tumor growth.
- The lectin-like domain of TM was essential for its cell adhesion function.
- Carbohydrates like mannose and chondroitin sulfates inhibited TM-mediated adhesion.
Conclusions:
- Thrombomodulin functions as a Ca2+-dependent cell-to-cell adhesion molecule.
- The lectin-like domain of TM is critical for mediating cell adhesion through carbohydrate binding.
- TM plays a role in regulating cell growth, tissue integrity, and potentially tumor progression.