Prolyl isomerase Pin1 enhances osteoblast differentiation through Runx2 regulation.

Peptidyl-prolyl isomerase 1 (Pin1) is the only enzyme known to catalyze isomerization of the pSer/Thr-Pro peptide bond. Pin1 induces conformational change of substrates and subsequently regulates diverse cellular processes. However, its role in osteoblast differentiation is not well understood. Here we show that Pin1 enhances osteoblast differentiation. Pin1 interacts and affects the protein stability and transcriptional activity of an important osteogenic transcriptional factor Runx2. Our results indicate that this regulation is likely due to suppression of poly-ubiquitination-mediated proteasomal degradation of Runx2. Our current finding suggests that Pin1 is a novel regulator of osteoblast differentiation that acts through the regulation of Runx2 function.