Regulation of ATPase activity of transglutaminase 2 by MT1-MMP: Implications for mineralization of MC3T3-E1 osteoblast cultures

• Published in: Journal of cellular physiology Vol. 223; no. 1; pp. 260 - 269
• Main Authors: Nakano, Yukiko, Forsprecher, Jennifer, Kaartinen, Mari T.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.04.2010
• Subjects: 3T3 Cells; Adenosine Triphosphate - metabolism; Animals; Binding Sites; Calcification, Physiologic; Calcium - metabolism; Enzyme Activation; GTP-Binding Proteins - chemistry; GTP-Binding Proteins - metabolism; Matrix Metalloproteinase 14 - metabolism; Mice; Molecular Weight; Osteoblasts - enzymology; Peptide Fragments; Phosphates - metabolism; Protein Processing, Post-Translational; Time Factors; Transglutaminases - chemistry; Transglutaminases - metabolism
• ISSN: 0021-9541; 1097-4652
• DOI: 10.1002/jcp.22034

A pro‐mineralization function for transglutaminase 2 (TG2) has been suggested in numerous studies related to bone, cartilage, and vascular calcification. TG2 is an enzyme which can perform protein crosslinking functions, or act as a GTPase/ATPase depending upon different stimuli. We have previously demonstrated that TG2 can act as an ATPase in a Ca2+‐rich environment and that it can regulate phosphate levels in osteoblast cultures. In this study, we investigate the role MT1‐MMP in regulating the ATPase activity of TG2. We report that proteolytic cleavage of TG2 by MT1‐MMP in vitro results in nearly a 3‐fold increase in the ATPase activity of TG2 with a concomitant reduction in its protein‐crosslinking activity. We show that MC3T3‐E1 osteoblasts secreted full‐length TG2 and major smaller fragments of 66 and 56 kDa, the latter having ATP‐binding abilities. MT1‐MMP inhibition by a neutralizing antibody suppressed mineralization of osteoblast cultures to 35% of control, and significantly reduced phosphate levels in conditioned medium (CM). Furthermore, MT1‐MMP inhibition abolished two of TG2 fragments in the cultures, one of which, the 56‐kDa fragment, has ATPase activity. Neutralization of MT1‐MMP at early phases of mineralization significantly reduced mineral deposition, but had no effect in later phases implying MT1‐MMP and TG2 might contribute to the initiation of mineralization. The cleavage of TG2 by MT1‐MMP likely occurs on the cell surface/pericellular matrix where MT1‐MMP and TG2 were co‐localized. Based on these data, we propose that MT1‐MMP modulates the extracellular function TG2 as part of a regulatory mechanism activates the pro‐mineralization function of TG2. J. Cell. Physiol. 223: 260–269, 2010. © 2009 Wiley‐Liss, Inc.