title: Use of Bmp1/Tll1 doubly homozygous null mice and proteomics to identify and validate in vivo substrates of bone morphogenetic protein 1/tolloid-like metalloproteinases.
abstract: Bone morphogenetic protein 1 (BMP-1) and mammalian Tolloid (mTLD), two proteinases encoded by Bmp1, provide procollagen C-proteinase (pCP) activity that converts procollagens I to III into the major fibrous components of mammalian extracellular matrix (ECM). Yet, although Bmp1(-/-) mice have aberrant collagen fibrils, they have residual pCP activity, indicative of genetic redundancy. Mammals possess two additional proteinases structurally similar to BMP-1 and mTLD: the genetically distinct mammalian Tolloid-like 1 (mTLL-1) and mTLL-2. Mice lacking the mTLL-1 gene Tll1 are embryonic lethal but have pCP activity levels similar to those of the wild type, suggesting that mTLL-1 might not be an in vivo pCP. In vitro studies have shown BMP-1 and mTLL-1 capable of cleaving Chordin, an extracellular antagonist of BMP signaling, suggesting that these proteases might also serve to modulate BMP signaling and to coordinate the latter with ECM formation. However, in vivo evidence of roles for BMP-1 and mTLL-1 in BMP signaling in mammals is lacking. To remove functional redundancy obscuring the in vivo functions of BMP-1-related proteases in mammals, we here characterize Bmp1 Tll1 doubly null mouse embryos. Although these appear morphologically indistinguishable from Tll1(-/-) embryos, biochemical analysis of cells derived from doubly null embryos shows functional redundancy removed to an extent enabling us to demonstrate that (i) products of Bmp1 and Tll1 are responsible for in vivo cleavage of Chordin in mammals and (ii) mTLL-1 is an in vivo pCP that provides residual activity observed in Bmp1(-/-) embryos. Removal of functional redundancy also enabled use of Bmp1(-/-) Tll1(-/-) cells in a proteomics approach for identifying novel substrates of Bmp1 and Tll1 products.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: William N
authors.initials: WN
authors.lastname: Pappano
authors.forename: Barry M
authors.initials: BM
authors.lastname: Steiglitz
authors.forename: Ian C
authors.initials: IC
authors.lastname: Scott
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Keene
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Greenspan
mesh_terms: D000483:Alleles; D000818:Animals; D015153:Blotting, Western; D055395:Bone Morphogenetic Protein 1; D019485:Bone Morphogenetic Proteins / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D024161:Collagen Type XI / Q000737:chemistry; D003470:Culture Media / Q000494:pharmacology; D020405:Dermis / Q000648:ultrastructure; D015180:Electrophoresis, Gel, Two-Dimensional; D004817:Epidermis / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000378:metabolism; D005656:Fungal Proteins; D005838:Genotype; D006023:Glycoproteins / Q000378:metabolism* / Q000502:physiology; D006720:Homozygote; D015151:Immunoblotting; D036341:Intercellular Signaling Peptides and Proteins; D013058:Mass Spectrometry; D008666:Metalloendopeptidases / Q000235:genetics* / Q000378:metabolism; D045726:Metalloproteases; D051379:Mice; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000502:physiology; D008957:Models, Genetic; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011506:Proteins / Q000235:genetics* / Q000502:physiology; D020543:Proteome; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013379:Substrate Specificity; D013997:Time Factors; D055394:Tolloid-Like Metalloproteinases
chemical_list: D019485:Bone Morphogenetic Proteins; D024161:Collagen Type XI; D003470:Culture Media; D005656:Fungal Proteins; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011506:Proteins; D020543:Proteome; D003094:Collagen; C054234:chordin; D020928:Mitogen-Activated Protein Kinases; C102726:Pmk1 protein, Magnaporthe grisea; D045726:Metalloproteases; D055394:Tolloid-Like Metalloproteinases; D008666:Metalloendopeptidases; C484477:Tll1 protein, mouse; C121764:Tll2 protein, mouse; C525707:Bmp1 protein, mouse; D055395:Bone Morphogenetic Protein 1