Transforming Growth Factor-β Regulation of Bone Morphogenetic Protein-1/Procollagen C-proteinase and Related Proteins in Fibrogenic Cells and Keratinocytes*
- Seungbok Lee‡,
- David E. Solow-Cordero§,
- Efrat Kessler¶,
- Kazuhiko Takahara‡ and
- Daniel S. Greenspan‡‖
- From the ‡Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, Wisconsin 53706,§FibroGen Inc., South San Francisco, California 94080, and the ¶Maurice and Gabriela Goldschleger Eye Research Institute, Tel Aviv University Faculty of Medicine, Sheba Medical Center, Tel Hashomer 52621, Israel
Abstract
Transforming growth factor-β1 (TGF-β1) induces increased extracellular matrix deposition. Bone morphogenetic protein-1 (BMP-1) also plays key roles in regulating vertebrate matrix deposition; it is the procollagen C-proteinase (PCP) that processes procollagen types I–III, and it may also mediate biosynthetic processing of lysyl oxidase and laminin 5. Here we show that BMP-1 is itself up-regulated by TGF-β1 and that secreted BMP-1, induced by TGF-β1, is either processed to an active form or remains as unprocessed proenzyme, in a cell type-dependent manner. In MG-63 osteosacrcoma cells, TGF-β1 elevated levels of BMP-1 mRNA ∼7-fold and elevated levels of mRNA for mammalian tolloid (mTld), an alternatively spliced product of the BMP1 gene, to a lesser extent. Induction of RNA was dose- and time-dependent and cycloheximide-inhibitable. Secreted BMP-1 and mTld, induced by TGF-β1 in MG-63 and other fibrogenic cell cultures, were predominantly in forms in which proregions had been removed to yield activated enzyme. TGF-β1 treatment also induced procollagen N-proteinase activity in fibrogenic cultures, while expression of the procollagen C-proteinase enhancer (PCPE), a glycoprotein that stimulates PCP activity, was unaffected. In contrast to fibrogenic cells, keratinocytes lacked detectable PCPE under any culture conditions and were induced by TGF-β1 to secrete BMP-1 and mTld predominantly as unprocessed proenzymes.
Footnotes
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↵* This work was supported by National Institutes of Health Grants AR43621 and GM46846 (to D. S. G.), by FibroGen Inc., and by United States-Israel Binational Science Foundation (Jerusalem, Israel) Grant 89-00498 (to E. K. and D. S. G.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‖ To whom correspondence should be addressed: Dept. of Pathology and Laboratory Medicine, University of Wisconsin, 1300 University Ave., Madison, WI 53706. Tel.: 608-262-4676; Fax: 608-265-3301;dsgreens{at}facstaff.wisc.edu.
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↵1 The abbreviations used are: BMP-1, bone morphogenetic protein-1; TGF-β, transforming growth factor-β; mTld, mammalian tolloid; N-propeptide, amino-terminal propeptide; C-propeptide, carboxyl-terminal propeptide; pNα(I), processing intermediate of pro-α1(I) collagen that contains the N- but not the C-propeptide; pCα1(I), processing intermediate of pro-α1(I) collagen that contains the C- but not the N-propeptide; C-telopeptide, nonhelical sequence remaining at the carboxyl-terminus of the pro-α1(I) chain upon proteolytic removal of the C-propeptide; α1(I), fully processed pro-α1(I) chain from which both the N- and C-propeptides have been removed; PCP, procollagen C-proteinase; PCPE, procollagen C-proteinase enhancer; PNP, procollagen N-proteinase; bp, base pair(s); kb, kilobase; PAGE, polyacrylamide electrophoresis; PBS, phosphate-buffered saline.
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↵2 K. Takahara and D. S. Greenspan, unpublished observations.
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↵3 I. Nunes, K. Takahara, D. Rifkin, and D. S. Greenspan, unpublished observations.
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- Received February 28, 1997.
- Revision received April 22, 1997.
