Platelet-secreted thrombospondin (TSP) enhances cell adhesion to surfaces. This protein
Area of Science:
Cell biology
Biochemistry
Hematology
Background:
The physiological role of platelet-secreted thrombospondin (TSP) remains largely unknown.
TSP is hypothesized to play a role in platelet aggregation and cellular adhesion.
Purpose of the Study:
To investigate the cell adhesion-promoting properties of TSP.
To characterize the nature of the TSP cell surface receptor.
Main Methods:
TSP was isolated from human platelets.
In vitro cell-substratum adhesion assays were performed using various cell types.
Adhesion assays were conducted to rule out contamination by other adhesion proteins.
Main Results:
TSP significantly promoted the adhesion of platelets, melanoma cells, muscle cells, endothelial cells, fibroblasts, and epithelial cells to substratum.
TSP's adhesion-promoting activity was found to be species-independent and specific.
The results indicated that TSP's activity was not due to contamination by fibronectin, vitronectin, laminin, or platelet factor 4.
A proteinaceous cell surface receptor for TSP was identified, distinct from the fibronectin receptor.
Conclusions:
TSP is a potent promoter of cell-substratum adhesion for a wide range of cell types.
TSP functions independently of other known adhesion molecules like fibronectin.
A novel TSP-specific cell surface receptor mediates its adhesive functions.
