Insights into the association of Gla-rich protein and osteoarthritis, novel splice variants and γ-carboxylation status. | - CCMAR -

Journal Article

TitleInsights into the association of Gla-rich protein and osteoarthritis, novel splice variants and γ-carboxylation status.
Publication TypeJournal Article
AuthorsRafael, MS, Cavaco, S, Viegas, CSB, Santos, S, Ramos, A, Willems, BAG, Herfs, M, Theuwissen, E, Vermeer, C, Simes, DC
Year of Publication2014
JournalMol Nutr Food Res
Date Published2014 Aug
KeywordsAged, Alternative Splicing, Amino Acid Sequence, Animals, Calcinosis, Cartilage, Female, Glutamic Acid, HEK293 Cells, Humans, Male, Mice, Molecular Sequence Data, Organ Specificity, Osteoarthritis, Protein Processing, Post-Translational, Proteins, Recombinant Proteins, Sequence Alignment, Species Specificity

SCOPE: Gla-rich protein (GRP) is a vitamin K dependent protein, characterized by a high density of γ-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 γ-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 γ-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.


Alternate JournalMol Nutr Food Res
PubMed ID24867294