TY - JOUR
T1 - Insights into the association of Gla-rich protein and osteoarthritis, novel splice variants and gamma-carboxylation status
AU - Rafael, Marta S.
AU - Cavaco, Sofia
AU - Viegas, Carla S. B.
AU - Santos, Sofia
AU - Ramos, Acacio
AU - Willems, Brecht A. G.
AU - Herfs, Marjolein
AU - Theuwissen, Elke
AU - Vermeer, Cees
AU - Simes, Dina C.
PY - 2014/8
Y1 - 2014/8
N2 - Scope: Gla-rich protein (GRP) is a vitamin K dependent protein, characterized by a high density of gamma-carboxylated Glu residues, shown to accumulate in mouse and sturgeon cartilage and at sites of skin and vascular calcification in humans. Therefore, we investigated the involvement of GRP in pathological calcification in osteoarthritis (OA). Methods and results: Comparative analysis of GRP patterning at transcriptional and translational levels was performed between controls and OA patients. Using a RT-PCR strategy we unveiled two novel splice variants in human-GRP-F5 and F6-potentially characterized by the loss of full gamma-carboxylation and secretion functional motifs. GRP-F1 is shown to be the predominant splice variant expressed in mouse and human adult tissues, particularly in OA cartilage, while an overexpressing human cell model points it as the major gamma-carboxylated isoform. Using validated conformational antibodies detecting carboxylated or undercarboxylated GRP (c/uc GRP), we have demonstrated cGRP accumulation in controls, whereas ucGRP was the predominant form in OA-affected tissues, colocalizing at sites of ectopic calcification. Conclusion: Overall, our results indicate the predominance of GRP-F1, and a clear association of ucGRP with OA cartilage and synovial membrane. Levels of vitamin K should be further assessed in these patients to determine its potential therapeutic use as a supplement in OA treatment.
AB - Scope: Gla-rich protein (GRP) is a vitamin K dependent protein, characterized by a high density of gamma-carboxylated Glu residues, shown to accumulate in mouse and sturgeon cartilage and at sites of skin and vascular calcification in humans. Therefore, we investigated the involvement of GRP in pathological calcification in osteoarthritis (OA). Methods and results: Comparative analysis of GRP patterning at transcriptional and translational levels was performed between controls and OA patients. Using a RT-PCR strategy we unveiled two novel splice variants in human-GRP-F5 and F6-potentially characterized by the loss of full gamma-carboxylation and secretion functional motifs. GRP-F1 is shown to be the predominant splice variant expressed in mouse and human adult tissues, particularly in OA cartilage, while an overexpressing human cell model points it as the major gamma-carboxylated isoform. Using validated conformational antibodies detecting carboxylated or undercarboxylated GRP (c/uc GRP), we have demonstrated cGRP accumulation in controls, whereas ucGRP was the predominant form in OA-affected tissues, colocalizing at sites of ectopic calcification. Conclusion: Overall, our results indicate the predominance of GRP-F1, and a clear association of ucGRP with OA cartilage and synovial membrane. Levels of vitamin K should be further assessed in these patients to determine its potential therapeutic use as a supplement in OA treatment.
KW - Alternative splicing
KW - gamma-Carboxylation
KW - Gla-rich protein
KW - Osteoarthritis
KW - Vitamin K
U2 - 10.1002/mnfr.201300941
DO - 10.1002/mnfr.201300941
M3 - Article
C2 - 24867294
SN - 1613-4125
VL - 58
SP - 1636
EP - 1646
JO - Molecular Nutrition & Food Research
JF - Molecular Nutrition & Food Research
IS - 8
ER -