Dentin sialophosphoprotein is a potentially latent bioactive protein in dentin

Dentin sialophosphoprotein (DSPP) belongs to the family of small integrin-binding ligand N-linked glycoproteins (SIBLINGs), which share common biochemical features such as an arginine-glycine-aspartic acid (RGD) integrin-binding site. However, amino acid sequence analyses suggest that DSPP has lost some common features, but acquired other unique features, such as repeat sequences of serine-serine-aspartic acid (SDrr) that are not observed in other SIBLINGs proteins.

We review the biochemical features of DSPP using genetically modified mice and proteomic analyses. DSPP of some species lack the RGD sites unlike other SIBLING proteins such as dentin matrix protein-1 (DMP-1) and bone sialoprotein (BSP). We previously identified that mouse and human RGD domains in DSPP required the cleavage of an Ala-Ser peptide bond, next to the RGD domains, to become active. Other species such as bovine, sheep, and bears, possess a Thr-Ser bond next to the RGD domain, which is intrinsically unable to sequester the ability of the RGD domain. To predict the functional importance of certain proteins/domains based on evolutionary conservation rates, the RGD domain of DSPP did not appear to have pivotal roles compared to other SIBLINGs. However, upon investigating the peptide bond next to the RGD domains of DSPP in 37 species, we found most catarrhini, in which humans are classified, possess the Ala-Ser bond.

The functions of DSPP for integrin-mediated signaling possibly arize from the proteolytic cleavage of the peptide bonds close to the RGD domain and induce reactionary dentinogenesis in vivo.