Identification and characterization of glycation adducts on osteocalcin

Abstract

Osteocalcin is an important extracellular matrix bone protein that contributes to the structural properties of bone through its interactions with hydroxyapatite mineral and with collagen I. This role may be affected by glycation, a labile modification the levels of which has been shown to correlate with bone fragility. Glycation starts with the spontaneous addition of a sugar onto a free amine group on a protein, forming an Amadori product, and then proceeds through several environment-dependent stages resulting in the formation of an advanced glycation end product. Here, we induce the first step of this modification on synthetic osteocalcin, and then use multiple mass spectrometry fragmentation techniques to determine the location of this modification. Collision-induced dissociation resulted in spectra dominated by neutral loss, and was unable to identify Amadori products. Electron-transfer dissociation showed that the Amadori product formed solely on osteocalcin’s N-terminus. This suggests that the glycation of osteocalcin is unlikely to interfere with osteocalcin’s interaction with hydroxyapatite. Instead, glycation may interfere with its interaction with collagen I or another bone protein, osteopontin. Potentially, the levels of glycated osteocalcin fragments released from bone during bone resorption could be used to assess bone quality, should the N-terminal fragments be targeted.

FBXW2 localizes with osteocalcin in bovine periosteum on culture dishes as visualized by double immunostaining

“…5 ). The interaction between OC and other proteins, particularly during glucose metabolism, has been studied ( Garbossa and Folli, 2017 ; Kanazawa, 2015 , 2017 ; Levinger et al., 2017 ; Liu et al., 2015 ; Takeno et al., 2018 ; Thomas et al., 2017 ), whereas the interaction between OC and FBXW2 has not been previously studied. To the author's knowledge, this is the first study to reveal an interaction between OC and FBXW2.…”

The structural role of osteocalcin in bone biomechanics and its alteration in Type-2 Diabetes

“…Although there are limited evidence of OC glycation in the literature 31,32 , a recent experimental study has demonstrated that OC can become glycated through a post-translational modification at the N-terminus, which could have important implications on energy dissipation potential of this NCP. While this study suggests that this glycation was unlikely to interfere with OC's interaction with HAp, it is notable that these findings were based on a fragmented OC protein in which the fragmentation occurred between 19 and 20 residues.…”

The Interaction between Bmal1 and Per2 in Mouse BMSC Osteogenic Differentiation

“…Output signals from the suprachiasmatic nuclei (SCN) are believed to transmit standard circadian time to peripheral tissues through humoral routes and the sympathetic nervous system [ 23 , 24 ]. Some papers have indicated that the sympathetic nervous system mediates the expression of core clock genes and regulates bone remodeling [ 25 ].…”