The BMP antagonist gremlin 1 contributes to the development of cortical excitatory neurons, motor balance and fear responses.

Bone morphogenetic protein (BMP) signaling is required for early forebrain development and cortical formation. How the endogenous modulators of BMP signaling regulate the structural and functional maturation of the developing brain remains unclear. Here, we show that expression of the BMP antagonist Grem1 marks committed layer V and VI glutamatergic neurons in the embryonic mouse brain. Lineage tracing of Grem1-expressing cells in the embryonic brain was examined by administration of tamoxifen to pregnant Grem1creERT; Rosa26LSLTdtomato mice at 13.5 days post coitum (dpc), followed by collection of embryos later in gestation. In addition, at 14.5 dpc, bulk mRNA-seq analysis of differentially expressed transcripts between FACS-sorted Grem1-positive and -negative cells was performed. We also generated Emx1-cre-mediated Grem1 conditional knockout mice (Emx1-Cre;Grem1flox/flox) in which the Grem1 gene was deleted specifically in the dorsal telencephalon. Grem1Emx1cKO animals had reduced cortical thickness, especially layers V and VI, and impaired motor balance and fear sensitivity compared with littermate controls. This study has revealed new roles for Grem1 in the structural and functional maturation of the developing cortex.

Bone morphogenetic protein 1 cleaves the linker region between ligand-binding repeats 4 and 5 of the LDL receptor and makes the LDL receptor non-functional.

The cell-surface low-density lipoprotein receptor (LDLR) internalizes low-density lipoprotein (LDL) by receptor-mediated endocytosis and plays a key role in the regulation of plasma cholesterol levels. The ligand-binding domain of the LDLR contains seven ligand-binding repeats of approximately 40 residues each. Between ligand-binding repeats 4 and 5, there is a 10-residue linker region that is subject to enzymatic cleavage. The cleaved LDLR is unable to bind LDL. In this study, we have screened a series of enzyme inhibitors in order to identify the enzyme that cleaves the linker region. These studies have identified bone morphogenetic protein 1 (BMP1) as being the cleavage enzyme. This conclusion is based upon the use of the specific BMP1 inhibitor UK 383367, silencing of the BMP1 gene by the use of siRNA or CRISPR/Cas9 technology and overexpression of wild-type BMP1 or the loss-of-function mutant E214A-BMP1. We have also shown that the propeptide of BMP1 has to be cleaved at RSRR120↓ by furin-like proprotein convertases for BMP1 to have an activity towards the LDLR. Targeting BMP1 could represent a novel strategy to increase the number of functioning LDLRs in order to lower plasma LDL cholesterol levels. However, a concern by using BMP1 inhibitors as cholesterol-lowering drugs could be the risk of side effects based on the important role of BMP1 in collagen assembly.

Extracellular BMP1 is the major proteinase for COOH-terminal proteolysis of type I procollagen in lung fibroblasts.

Proteolytic processing of procollagens is a central step during collagen fibril formation. Bone morphogenic protein 1 (BMP1) is a metalloprotease that plays an important role in the cleavage of carboxy-terminal (COOH-terminal) propeptides from procollagens. Although the removal of propeptides is required to generate mature collagen fibrils, the contribution of BMP1 to this proteolytic process and its action site remain to be fully determined. In this study, using postnatal lung fibroblasts as a model system, we showed that genetic ablation of Bmp1 in primary murine lung fibroblasts abrogated COOH-terminal cleavage from type I procollagen as measured by COOH-terminal propeptide of type I procollagen (CICP) production. We also showed that inhibition of BMP1 by siRNA-mediated knockdown or small-molecule inhibitor reduced the vast majority of CICP production and collagen deposition in primary human lung fibroblasts. Furthermore, we discovered and characterized two antibody inhibitors for BMP1. In both postnatal lung fibroblast and organoid cultures, BMP1 blockade prevented CICP production. Together, these findings reveal a nonredundant role of extracellular BMP1 to process CICP in lung fibroblasts and suggest that development of antibody inhibitors is a viable pharmacological approach to target BMP1 proteinase activity in fibrotic diseases.

BMP1 inhibitor UK383,367 attenuates renal fibrosis and inflammation in CKD.

Renal fibrosis is a key pathological phenomenon of chronic kidney disease (CKD) contributing to the progressive loss of renal function. UK383,367 is a procollagen C proteinase inhibitor that has been selected as a candidate for dermal antiscarring agents, whereas its role in renal fibrosis is unclear. In the present study, UK383,367 was applied to a CKD mouse model of unilateral ureteral obstruction (UUO) and cell lines of renal tubular epithelial cells (mouse proximal tubular cells) and renal fibroblast cells (NRK-49F cells) challenged by transforming growth factor-ß1. In vivo, bone morphogenetic protein 1, the target of UK383,367, was significantly enhanced in UUO mouse kidneys and renal biopsies from patients with CKD. Strikingly, UK383,367 administration ameliorated tubulointerstitial fibrosis as shown by Masson's trichrome staining in line with the blocked expression of collagen type I/III, fibronectin, and α-smooth muscle actin in the kidneys from UUO mice. Similarly, the enhanced inflammatory factors in obstructed kidneys were also blunted. In vitro, UK383,367 pretreatment inhibited the induction of collagen type I/III, fibronectin, and α-smooth muscle actin in both mouse proximal tubular cells and NRK-49F cells treated with transforming growth factor-ß1. Taken together, these findings indicate that the bone morphogenetic protein 1 inhibitor UK383,367 could serve as a potential drug in antagonizing CKD renal fibrosis by acting on the maturation and deposition of collagen and the subsequent profibrotic response and inflammation.

Yes-associated protein 1 promotes the differentiation and mineralization of cementoblast.

Yes-associated protein 1 (YAP1) transcriptional coactivator is a mediator of mechanosensitive signaling. Cementum, which covers the tooth root surface, continuously senses external mechanical stimulation. Cementoblasts are responsible for the mineralization and maturation of the cementum. However, the effect of YAP1 on cementoblast differentiation remains largely unknown. In this study, we initially demonstrated that YAP1 overexpression enhanced the mineralization ability of cementoblasts. YAP1 upregulated the mRNA and protein expression of several cementogenesis markers, such as alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), osteocalcin (OCN), and dentin matrix acidic phosphoprotein 1 (DMP1). The YAP1 overexpression group showed higher intensities of ALP and Alizarin red stain than the YAP1-knockdown group. Unexpectedly, a sharp increase in the expression of dentin sialophosphoprotein (DSPP) was induced by the overexpression of YAP1. Knockdown of YAP1 suppressed DSPP transcriptional activity. YAP1 overexpression activated Smad-dependent BMP signaling and slightly inhibited Erk1/2 signaling pathway activity. Treatment with specific BMP antagonist (LDN193189) prevented the upregulation of the mRNA levels of ALP, RUNX2, and OCN, as well as intensity of ALP-stained and mineralized nodules in cementoblasts. The Erk1/2 signaling pathway inhibitor (PD 98,059) upregulated these cementogenesis markers. Thus, our study suggested that YAP1 enhanced cementoblast mineralization in vitro. YAP1 exerted its effect on the cementoblast partly by regulating the Smad-dependent BMP and Erk1/2 signaling pathways.

Enzymatic regulation of pattern: BMP4 binds CUB domains of Tolloids and inhibits proteinase activity.

In Xenopus embryos, a dorsal-ventral patterning gradient is generated by diffusing Chordin/bone morphogenetic protein (BMP) complexes cleaved by BMP1/Tolloid metalloproteinases in the ventral side. We developed a new BMP1/Tolloid assay using a fluorogenic Chordin peptide substrate and identified an unexpected negative feedback loop for BMP4, in which BMP4 inhibits Tolloid enzyme activity noncompetitively. BMP4 binds directly to the CUB (Complement 1r/s, Uegf [a sea urchin embryonic protein] and BMP1) domains of BMP1 and Drosophila Tolloid with high affinity. Binding to CUB domains inhibits BMP4 signaling. These findings provide a molecular explanation for a long-standing genetical puzzle in which antimorphic Drosophila tolloid mutant alleles displayed anti-BMP effects. The extensive Drosophila genetics available supports the relevance of the interaction described here at endogenous physiological levels. Many extracellular proteins contain CUB domains; the binding of CUB domains to BMP4 suggests a possible general function in binding transforming growth factor-beta (TGF-beta) superfamily members. Mathematical modeling indicates that feedback inhibition by BMP ligands acts on the ventral side, while on the dorsal side the main regulator of BMP1/Tolloid enzymatic activity is the binding to its substrate, Chordin.

Loss of the BMP antagonist, SMOC-1, causes Ophthalmo-acromelic (Waardenburg Anophthalmia) syndrome in humans and mice.

Ophthalmo-acromelic syndrome (OAS), also known as Waardenburg Anophthalmia syndrome, is defined by the combination of eye malformations, most commonly bilateral anophthalmia, with post-axial oligosyndactyly. Homozygosity mapping and subsequent targeted mutation analysis of a locus on 14q24.2 identified homozygous mutations in SMOC1 (SPARC-related modular calcium binding 1) in eight unrelated families. Four of these mutations are nonsense, two frame-shift, and two missense. The missense mutations are both in the second Thyroglobulin Type-1 (Tg1) domain of the protein. The orthologous gene in the mouse, Smoc1, shows site- and stage-specific expression during eye, limb, craniofacial, and somite development. We also report a targeted pre-conditional gene-trap mutation of Smoc1 (Smoc1(tm1a)) that reduces mRNA to ∼10% of wild-type levels. This gene-trap results in highly penetrant hindlimb post-axial oligosyndactyly in homozygous mutant animals (Smoc1(tm1a/tm1a)). Eye malformations, most commonly coloboma, and cleft palate occur in a significant proportion of Smoc1(tm1a/tm1a) embryos and pups. Thus partial loss of Smoc-1 results in a convincing phenocopy of the human disease. SMOC-1 is one of the two mammalian paralogs of Drosophila Pentagone, an inhibitor of decapentaplegic. The orthologous gene in Xenopus laevis, Smoc-1, also functions as a Bone Morphogenic Protein (BMP) antagonist in early embryogenesis. Loss of BMP antagonism during mammalian development provides a plausible explanation for both the limb and eye phenotype in humans and mice.

Exogenously administered secreted frizzled related protein 2 (Sfrp2) reduces fibrosis and improves cardiac function in a rat model of myocardial infarction.

Secreted frizzled related protein 2 (Sfrp2) is known as an inhibitor for the Wnt signaling. In recent studies, Sfrp2 has been reported to inhibit the activity of Xenopus homolog of mammalian Tolloid-like 1 metalloproteinase. Bone morphogenic protein 1 (Bmp1)/Tolloid-like metalloproteinase plays a key role in the regulation of collagen biosynthesis and maturation after tissue injury. Here, we showed both endogenous Sfrp2 and Bmp1 protein expressions were up-regulated in rat heart after myocardial infarction (MI). We hypothesize that Sfrp2 could inhibit mammalian Bmp1 activity and, hence, the exogenous administration of Sfrp2 after MI would inhibit the deposition of mature collagen and improve heart function. Using recombinant proteins, we demonstrated that Sfrp2, but not Sfrp1 or Sfrp3, inhibited Bmp1 activity in vitro as measured by a fluorogenic peptide based procollagen C-proteinase activity assay. We also demonstrated that Sfrp2 at high concentration inhibited human and rat type I procollagen processing by Bmp1 in vitro. We further showed that exogenously added Sfrp2 inhibited type I procollagen maturation in primary cardiac fibroblasts. Two days after direct injection into the rat infarcted myocardium, Sfrp2 inhibited MI-induced type I collagen deposition. As early as 2 wk after injection, Sfrp2 significantly reduced left ventricular (LV) fibrosis as shown by trichrome staining. Four weeks after injection, Sfrp2 prevented the anterior wall thinning and significantly improved cardiac function as revealed by histological analysis and echocardiographic measurement. Our study demonstrates Sfrp2 at therapeutic doses can inhibit fibrosis and improve LV function at a later stage after MI.

Design and synthesis of procollagen C-proteinase inhibitors.

Non-peptidic inhibitors of procollagen C-proteinase (PCP) were designed from substrate leads. Compounds were optimized for potency and selectivity, with N-substituted aryl sulfonamide hydroxamates having the best combination of these properties. Compounds 89 and 60 have IC(50) values of 10 and 80 nM, respectively, against PCP; excellent selectivity over MMP's 1, 2, and 9; and activity in cell-based collagen deposition assays.

Bone morphogenetic protein 1.3 inhibition decreases scar formation and supports cardiomyocyte survival after myocardial infarction.

Despite the high prevalence of ischemic heart diseases worldwide, no antibody-based treatment currently exists. Starting from the evidence that a specific isoform of the Bone Morphogenetic Protein 1 (BMP1.3) is particularly elevated in both patients and animal models of myocardial infarction, here we assess whether its inhibition by a specific monoclonal antibody reduces cardiac fibrosis. We find that this treatment reduces collagen deposition and cross-linking, paralleled by enhanced cardiomyocyte survival, both in vivo and in primary cultures of cardiac cells. Mechanistically, we show that the anti-BMP1.3 monoclonal antibody inhibits Transforming Growth Factor ß pathway, thus reducing myofibroblast activation and inducing cardioprotection through BMP5. Collectively, these data support the therapeutic use of anti-BMP1.3 antibodies to prevent cardiomyocyte apoptosis, reduce collagen deposition and preserve cardiac function after ischemia.

A single cell characterisation of human embryogenesis identifies pluripotency transitions and putative anterior hypoblast centre.

Following implantation, the human embryo undergoes major morphogenetic transformations that establish the future body plan. While the molecular events underpinning this process are established in mice, they remain unknown in humans. Here we characterise key events of human embryo morphogenesis, in the period between implantation and gastrulation, using single-cell analyses and functional studies. First, the embryonic epiblast cells transition through different pluripotent states and act as a source of FGF signals that ensure proliferation of both embryonic and extra-embryonic tissues. In a subset of embryos, we identify a group of asymmetrically positioned extra-embryonic hypoblast cells expressing inhibitors of BMP, NODAL and WNT signalling pathways. We suggest that this group of cells can act as the anterior singalling centre to pattern the epiblast. These results provide insights into pluripotency state transitions, the role of FGF signalling and the specification of anterior-posterior axis during human embryo development.

Blocking angiogenesis with peptides that inhibit the activity of procollagen C-endopeptidase.

Procollagen C-endopeptidase (BMP-1) is one of two key enzymes crucial for conversion of fibrillar procollagens to self-assembling collagen monomers. Recently, we have reported inhibition of the largest variant of BMP-1, a recombinant mammalian tolloid (mTld) in vitro, on procollagen type I using peptides with amino acid sequences in chordin conserved across different species. Here, we tested the same peptides as potent blockers of angiogenesis ex vivo in cultured rings of rat aorta, in vivo in chick embryos, and in vitro in cell cultures. Our results revealed that the peptides inhibited the angiogenic activity in rat aorta explants at micromolar concentrations; they also blocked blood vessel growth in chick embryos. The peptides were also tested on three types of human cells, e.g., umbilical vein endothelium, skin fibroblasts, and tumor HT-1080 cells. Since the three types of cells proliferated at a significantly lower rate or did not proliferate at all, we conclude that the anti-angiogenic effect observed in rat aorta ring explants and in chick embryos was related to inhibition of cell proliferation. In conclusion, we showed the ability to inhibit angiogenesis by blocking the activity of procollagen C-endopeptidase. The results strongly indicate crucial role(s) of this metalloproteinase in the formation of new blood vessels and maintenance of their growth.

Proteolysis of the low density lipoprotein receptor by bone morphogenetic protein-1 regulates cellular cholesterol uptake.

The development of cardiovascular disease is intimately linked to elevated levels of low-density lipoprotein (LDL) cholesterol in the blood. Hepatic LDL receptor (LDLR) levels regulate the amount of plasma LDL. We identified the secreted zinc metalloproteinase, bone morphogenetic protein 1 (BMP1), as responsible for the cleavage of human LDLR within its extracellular ligand-binding repeats at Gly171↓Asp172. The resulting 120 kDa membrane-bound C-terminal fragment (CTF) of LDLR had reduced capacity to bind LDL and when expressed in LDLR null cells had compromised LDL uptake as compared to the full length receptor. Pharmacological inhibition of BMP1 or siRNA-mediated knockdown prevented the generation of the 120 kDa CTF and resulted in an increase in LDL uptake into cells. The 120 kDa CTF was detected in the livers from humans and mice expressing human LDLR. Collectively, these results identify that BMP1 regulates cellular LDL uptake and may provide a target to modulate plasma LDL cholesterol.

Specific targeting of metzincin family members with small-molecule inhibitors: progress toward a multifarious challenge.

Zn-metalloproteinases are an important class of hydrolytic enzymes that are characterized by the presence of a catalytic zinc(II) atom in their active center which is fundamental for proteolytic activity. Metzincins, a superfamily of Zn-metalloproteinases with many structural and functional commonalities among its members, are responsible for the fine tuning of key physiological functions in mammals and the deregulation of their activity is directly connected to numerous inflammatory and degenerative diseases such as arthritis or cancer. Development of small-molecule exogenous inhibitors of metzincins able to re-establish normal proteolytic activity in pathological conditions has been a field of intense research effort for many years but applications in the clinic were not always successful. One of the main reasons for this failure is the uncontrolled action of these inhibitors on target as well as anti-target metzincin family members. Current medicinal efforts have been shifted to the discovery of target-specific inhibitors that will help to improve our understanding of metzincins biological function and provide the basis for the development of safer pharmaceutical agents. This review focuses on the cases of certain medicinally important metzincins [matrix metalloproteinases (MMPs), a disintegrin and metalloproteinases (ADAMs), ADAMs with thrombospondin motifs (ADAMTSs), and procollagen C-proteinase (PCP)] and summarizes the latest advances on the discovery of inhibitors of these enzymes that display improved selectivity profiles.