Matrix metalloproteinase processing of PTHrP yields a selective regulator of osteogenesis, PTHrP1–17
Parathyroid hormone-related protein (PTHrP) is a critical regulator of bone resorption and augments osteolysis in skeletal malignancies. Here we report that the mature PTHrP1–36 hormone is processed by matrix metalloproteinases to yield a stable product, PTHrP1–17. PTHrP1–17 retains the ability to signal through PTH1R to induce calcium flux and ERK phosphorylation but not cyclic AMP production or CREB phosphorylation. Notably, PTHrP1–17 promotes osteoblast migration and mineralization in vitro, and systemic administration of PTHrP1–17 augments ectopic bone formation in vivo. Further, in contrast to PTHrP1–36, PTHrP1–17 does not affect osteoclast formation/function in vitro or in vivo. Finally, immunoprecipitation-mass spectrometry analyses using PTHrP1–17-specific antibodies establish that PTHrP1–17 is indeed generated by cancer cells. Thus, matrix metalloproteinase-directed processing of PTHrP disables the osteolytic functions of the mature hormone to promote osteogenesis, indicating important roles for this circuit in bone remodelling in normal and disease contexts.