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J. Biol. Chem., Vol. 281, Issue 45, 34021-34031, November 10, 2006
Regulation of Bone Morphogenetic Protein-4 Activity by Sequence Elements within the Prodomain*From the Department of Cell and Developmental Biology, Oregon Health and Science University, Portland, Oregon 97239 Bone morphogenetic protein-4 (BMP-4) is synthesized as a large precursor protein, which undergoes proprotein convertase-mediated proteolytic maturation along the secretory pathway to release the active ligand. Pro-BMP-4 is initially cleaved at a consensus furin motif adjacent to the mature ligand domain (the S1 site), and this allows for subsequent cleavage at an upstream motif (the S2 site). This sequential cleavage liberates a small, evolutionarily conserved, prodomain fragment (the linker peptide) of unknown fate and function. Here we show that the linker domain is essential for proper folding, exit from the endoplasmic reticulum, and thus cleavage of the BMP-4 precursor when overexpressed in Xenopus oocytes and embryos but not in cultured mammalian cells. Mature BMP-4 synthesized from a precursor in which the S1 site is non-cleavable, such that the linker domain remains covalently attached to the ligand, has little or no activity in vivo. Finally, analysis of folding, cleavage, and bioactivity of chimeric precursors containing the BMP-7 prodomain and BMP-4 mature domain, or vice versa, with or without the BMP-4 linker domain revealed that the linker domain is only functional in the context of the BMP-4 prodomain, and that differential cleavage around this domain can regulate the activity of a heterologous ligand.
Received for publication, June 5, 2006 , and in revised form, August 23, 2006. * The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Both authors contributed equally to the work. 2 To whom correspondence should be addressed: Dept. of Cell and Developmental Biology, OR Health and Science University, 3181 S.W. Sam Jackson Park Rd., Portland, OR 97239. Tel.: 503-494-2492; Fax: 503-494-4253; E-mail: christia{at}ohsu.edu.
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