Journal Article
Title | Gla-rich protein acts as a calcification inhibitor in the human cardiovascular system. |
Publication Type | Journal Article |
Authors | Viegas, CSB, Rafael, MS, Enriquez, JL, Teixeira, A, Vitorino, R, Luís, IM, Costa, RM, Santos, S, Cavaco, S, Neves, J, Macedo, AL, Willems, BAG, Vermeer, C, Simes, DC |
Year of Publication | 2015 |
Journal | Arterioscler Thromb Vasc Biol |
Volume | 35 |
Issue | 2 |
Date Published | 2015 Feb |
Pagination | 399-408 |
ISSN | 1524-4636 |
Keywords | Actins, Adult, Aged, Aged, 80 and over, alpha-2-HS-Glycoprotein, Aorta, Aortic Valve, Aortic Valve Stenosis, Calcinosis, Calcium, Calcium-Binding Proteins, Case-Control Studies, Coronary Artery Disease, Coronary Vessels, Extracellular Matrix Proteins, Female, Gene Expression Regulation, Humans, Male, Middle Aged, Osteocalcin, Proteins, Tissue Culture Techniques, Vascular Calcification |
Abstract | OBJECTIVE: Vascular and valvular calcifications are pathological processes regulated by resident cells, and depending on a complex interplay between calcification promoters and inhibitors, resembling skeletal metabolism. Here, we study the role of the vitamin K-dependent Gla-rich protein (GRP) in vascular and valvular calcification processes.APPROACH AND RESULTS: Immunohistochemistry and quantitative polymerase chain reaction showed that GRP expression and accumulation are upregulated with calcification simultaneously with osteocalcin and matrix Gla protein (MGP). Using conformation-specific antibodies, both γ-carboxylated GRP and undercarboxylated GRP species were found accumulated at the sites of mineral deposits, whereas undercarboxylated GRP was predominant in calcified aortic valve disease valvular interstitial cells. Mineral-bound GRP, MGP, and fetuin-A were identified by mass spectrometry. Using an ex vivo model of vascular calcification, γ-carboxylated GRP but not undercarboxylated GRP was shown to inhibit calcification and osteochondrogenic differentiation through α-smooth muscle actin upregulation and osteopontin downregulation. Immunoprecipitation assays showed that GRP is part of an MGP-fetuin-A complex at the sites of valvular calcification. Moreover, extracellular vesicles released from normal vascular smooth muscle cells are loaded with GRP, MGP, and fetuin-A, whereas under calcifying conditions, released extracellular vesicles show increased calcium loading and GRP and MGP depletion.CONCLUSIONS: GRP is an inhibitor of vascular and valvular calcification involved in calcium homeostasis. Its function might be associated with prevention of calcium-induced signaling pathways and direct mineral binding to inhibit crystal formation/maturation. Our data show that GRP is a new player in mineralization competence of extracellular vesicles possibly associated with the fetuin-A-MGP calcification inhibitory system. GRP activity was found to be dependent on its γ-carboxylation status, with potential clinical relevance. |
DOI | 10.1161/ATVBAHA.114.304823 |
Sapientia | |
Alternate Journal | Arterioscler. Thromb. Vasc. Biol. |
PubMed ID | 25538207 |