DPP and DSP are necessary for maintaining TGF-β1 activity in dentin

Porcine dentin sialophosphoprotein (dspp) is the most abundant non-collagenous protein in dentin. it is processed by proteases into 3 independent proteins: dentin sialoprotein (dsp),dentin glycoprotein (dgp),and dentin phosphoprotein (dpp). we fractionated dpp and dsp along with tgf-β activity by ion exchange (ie) chromatography from developing pig molars and measured their alkaline phosphatase (alp)-stimulating activity in human periodontal (hpdl) cells with or without tgf-β receptor inhibitor. we then purified tgf- β-unbound or -bound dpp and dsp by reversephase high-performance liquid chromatography (rp-hplc) using the alp-hpdl system. the tgf-β isoform bound to dpp and dsp was identified as being tgf-β1 by both elisa and lc-ms/ ms analysis. we incubated carrier-free human recombinant tgf-β1 (cf-htgf-β1) with tgf-β- unbound dpp or dsp and characterized the binding on ie-hplc using the alp-hpdl system. when only cf-htgf-β1 was incubated,approximately 3.6% of the alp-stimulating activity remained. dpp and dsp rescued the loss of tgf- β1 activity. approximately 19% and 10% of the alp stimulating activities were retained by the binding of tgf-β to dpp and dsp,respectively. the type i collagen infrequently bound to cf-htgf-β1. we conclude that both dpp and dsp help retain tgf-β1 activity in porcine dentin. © international & american associations for dental research.