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Localization and characterization of a novel secreted protein SCUBE1 in human platelets
Cheng-Fen Tu1, Yueh-Hsing Su, Ya-Ni Huang
1Institute of Biomedical Sciences, Academia Sinica, and Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
Insights
Platelet-derived SCUBE1 (signal peptide, CUB, and EGF-like domain containing protein 1) acts as a novel adhesive molecule. Its fragments play roles in cardiovascular health and disease.
Area of Science:
- Vascular Biology
- Platelet Function
- Protein Biochemistry
Background:
- SCUBE1 (signal peptide, CUB, and EGF-like domain containing protein 1) is a novel secreted protein identified in the vascular system.
- Understanding SCUBE1's role is crucial for cardiovascular research.
Purpose of the Study:
- To investigate the expression and function of SCUBE1 in the vascular system.
- To determine SCUBE1's localization and potential roles in platelet biology and cardiovascular disease.
Main Methods:
- Immunohistochemistry and immunolocalization techniques were used to detect SCUBE1 protein.
- Quantitative real-time RT-PCR was employed to analyze SCUBE1 mRNA expression in platelets.
- Western blot analysis and platelet adhesion/agglutination assays were performed to study SCUBE1 function and fragments.
Main Results:
- SCUBE1 protein is primarily found in platelet-rich thrombi and stored within platelet alpha-granules.
- SCUBE1 is translocated to the platelet surface upon stimulation, and fragments are detected in thrombus.
- SCUBE1 was observed in the subendothelial matrix of atherosclerotic plaques, and its fragments promote platelet adhesion and agglutination.
Conclusions:
- Platelet-derived SCUBE1 functions as a novel adhesive molecule.
- Matrix-bound and soluble SCUBE1 fragments may have significant roles in cardiovascular physiology and pathology.
Objective:
The aim of the study was to investigate the protein expression and function of a novel secreted protein in the vascular system, named SCUBE1 for signal peptide, CUB (Complement proteins C1r/C1s, Uegf, and Bmp1) and epidermal growth factor-like (EGF)-like domain containing protein 1.
Methods And Results:
Immunohistochemical analysis demonstrated that the SCUBE1 staining is mainly confined to the intravascular platelet-rich thrombus in vascular tissue samples. While quantitative real-time RT-PCR verified that the SCUBE1 mRNA is expressed in human platelets, numerous immunolocalization techniques revealed that the preformed SCUBE1 protein is stored in the alpha-granules and translocated to the surface upon platelet stimulation. A smaller SCUBE1 fragment, possibly formed by limited proteolysis after being released from the storage granules, was detected in thrombus lysate by Western blot analysis. Interestingly, deposition of SCUBE1 into the subendothelial matrix of the atherosclerotic plaques was evidenced by immunohistochemistry. In addition, studies of platelet adhesion and ristocetin-induced platelet agglutination showed that fragments containing the amino-terminal EGF-like repeats were able to support platelet adhesion and enhance the ristocetin-induced platelet agglutination, respectively.
Conclusion:
These data suggest that platelet-derived SCUBE1 could function as a novel adhesive molecule and its matrix-bound and soluble fragments may play critical (patho)physiological roles in cardiovascular biology.
