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

Previously we found that the carboxyl-terminal propeptide of type I collage n (c-propeptide) is a major secretory protein of MC3T3-E1 osteoblastic cell s. In this study, we found that c-propeptide suppresses collagen synthesis and alkaline phosphatase activity of MC3T3-E1 osteoblastic cells at the ear ly -differentiated stage in a dose dependent manner. Mature osteoblasts did not respond to c-propeptide, These findings imply that c-propeptide modula tes the function of osteoblasts at an early differentiation stage. Transfor ming growth factor-beta (TGF-beta) 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-beta, and found that it enhanced the effe ct of TGF-beta. We conclude that c-propeptide is a physiological modulator of TGF-beta in bone metabolism. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.