BMP-4 is proteolytically activated by furin and/or PC6 during vertebrate embryonic development.
Bone morphogenetic protein-4 (BMP-4) is a multifunctional developmental regulator. BMP-4 is synthesized as an inactive precursor that is proteolytically activated by cleavage following the amino acid motif -Arg-Ser-Lys-Arg-. Very little is known about processing and secretion of BMPs. The proprotein convertases (PCs) are a family of seven structurally related serine endoproteases, at least one of which, furin, cleaves after the amino acid motif -Arg-X-Arg/Lys-Arg-. To examine potential roles of PCs during embryonic development we have misexpressed a potent protein inhibitor of furin, alpha1-antitrypsin Portland (alpha1-PDX) in early Xenopus embryos. Ectopic expression of alpha1-PDX phenocopies the effect of blocking endogenous BMP activity, leading to dorsalization of mesoderm and direct neural induction. alpha1-PDX-mediated neural induction can be reversed by co-expression of downstream components of the BMP-4 signaling pathway. Thus, alpha1-PDX can block BMP activity upstream of receptor binding, suggesting that it inhibits an endogenous BMP-4 convertase(s). Consistent with this hypothesis, alpha1-PDX prevents cleavage of BMP-4 in an oocyte translation assay. Using an in vitro digestion assay, we demonstrate that four members of the PC family have the ability to cleave BMP-4, but of these, only furin and PC6B are sensitive to alpha1-PDX. These studies provide the first in vivo evidence that furin and/or PC6 proteolytically activate BMP-4 during vertebrate embryogenesis.
Cui
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Department of Cell and Developmental Biology, Oregon Health Sciences University, School of Medicine, 3181 SW Sam Jackson Park Road, Portland, Oregon 97201-3098, USA.
Jean
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Thomas
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Christian
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D000818:Animals; D001483:Base Sequence; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D019070:Cell Lineage; D017931:DNA Primers; D004475:Ectoderm / Q000166:cytology; D004625:Embryo, Nonmammalian; D045683:Furin; D006868:Hydrolysis; D008648:Mesoderm / Q000166:cytology; D045702:Proprotein Convertase 5; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D015398:Signal Transduction; D013381:Subtilisins / Q000378:metabolism*; D014981:Xenopus / Q000196:embryology; D029867:Xenopus Proteins; D000515:alpha 1-Antitrypsin / Q000494:pharmacology
D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D017931:DNA Primers; D011498:Protein Precursors; D029867:Xenopus Proteins; D000515:alpha 1-Antitrypsin; C113421:alpha 1-antitrypsin Portland; C525812:bmp4 protein, Xenopus; D045702:Proprotein Convertase 5; D013381:Subtilisins; D045683:Furin