Carboxyl-terminal propeptide of type I collagen (c-propeptide) modulates the action of TGF-β on MC3T3-E1 osteoblastic cells

Abstract

Previously we found that the carboxyl-terminal propeptide of type I collagen (c-propeptide) is a major secretory protein of MC3T3-E1 osteoblastic cells. In this study, we found that c-propeptide suppresses collagen synthesis and alkaline phosphatase activity of MC3T3-E1 osteoblastic cells at the early-differentiated stage in a dose dependent manner. Mature osteoblasts did not respond to c-propeptide. These findings imply that c-propeptide modulates the function of osteoblasts at an early differentiation stage. Transforming growth factor-β (TGF-β) is stored in bone and released from bone matrix after the resorption by osteoclasts. We investigated the effect of c-propeptide on the action of TGF-β, and found that it enhanced the effect of TGF-β. We conclude that c-propeptide is a physiological modulator of TGF-β in bone metabolism.