Figure 2.

Mechanisms of parathyroid hormone–related protein (PTHrP) signaling in chondrocyte maturation. PTHrP can cyclin-D1–dependently induce degradation of runt-related transcription factor 2 and 3 (Runx2/3); down-regulate Runx2 expression through the protein kinase A (PKA) pathway; increase expression of zinc finger transcriptional coregulator 521 (Zfp521), which antagonizes Runx2 through histone deacetylase 4 (HDAC4); and promote dephosphorylation of HDAC4 and thus inhibit myocyte enhancer factor 2C (MEF2C) transcription. P represents phosphorylation.