Binding of procollagen C-proteinase enhancer-1 (PCPE-1) to heparin/heparan sulfate: properties and role in PCPE-1 interaction with cells

PCPE2: Expression of Multifunctional Extracellular Glycoprotein Associates With Diverse Cellular Functions

Procollagen C-endopeptidase enhancer 2, known as PCPE2 or PCOC2 (gene name, PCOLCE2) is a glycoprotein that resides in the extracellular matrix, and is similar in domain organization to PCPE1 / PCPE, PCOC1 (PCOLCE1 /PCOLCE). Due to the many similarities between the two related proteins, PCPE2 has been assumed to have biological functions similar to PCPE. PCPE is a well-established enhancer of procollagen processing activating the enzyme, BMP-1. However, reports show that PCPE2 has a strikingly different tissue expression profile compared to PCPE. With that in mind and given the paucity of published studies on PCPE2, this review examines the current literature citing PCPE2 and its association with specific cell types and signaling pathways. Additionally, this review will present a brief history of PCPE2's discovery, highlighting structural and functional similarities and differences compared to PCPE. Considering the widespread use of RNA sequencing techniques to examine associations between cell-specific gene expression and disease states, we will show that PCPE2 is repeatedly found as a differentially regulated gene (DEG) significantly associated with a number of cellular processes, well beyond the scope of procollagen fibril processing.

Combining sandblasting and pink anodisation of Ti implants as a promising method for improving fibroblast adhesion and immune response

This study examined the effect of combining the sandblasting and anodising of titanium alloys used in implants on the cell response and protein adsorption patterns. The titanium samples were divided into four groups depending on the surface treatment: machining (MC), pink anodisation (PA), sandblasting (MC04) and a combination of the last two (MC04 + PA). Their physicochemical properties were analysed by SEM/EDX, Raman, contact angle measurements and profilometry. In vitro responses were examined using human gingival fibroblastic (HGF) cells and THP-1 macrophages. Cytokine secretion, macrophage adhesion and gene expression were measured by ELISA, confocal microscopy and RT-PCR. Cell adhesion and collagen secretion were evaluated in HGF cultures. The adsorption of immune and regenerative proteins onto the surfaces was assessed employing nLC-MS/MS. MC04 + PA surfaces exhibited a change in the roughness, chemical composition and hydrophilicity of the material, showing more elongated HGF cells and a considerable increase in the area of cells exposed to the MC04 + PA surfaces. Moreover, cells cultured on MC04 + PA generally showed a reduction in the expression of proinflammatory genes (TNF-α, MCP-1, C5, NF-kB and ICAM-1) and an increase in the secretion of anti-inflammatory cytokines, such as IL-4. These results correlated with the proteomic data; we found preferential adsorption of proteins favouring cell adhesion, such as DSC1 and PCOC1. A considerable reduction in the adsorption of immunoglobulins and proteins associated with acute inflammatory response (including SAA4) was also observed. The study highlights the potential advantages of MC04 + PA surface treatment to modify dental implant abutments; it enhances their compatibility with soft tissues and reduces the inflammatory response.

Structural Insights into Endostatin-Heparan Sulfate Interactions Using Modeling Approaches

Glycosaminoglycans (GAGs) play a key role in a variety of biological processes in the extracellular matrix (ECM) via interactions with their protein targets. Due to their high flexibility, periodicity and electrostatics-driven interactions, GAG-containing complexes are very challenging to characterize both experimentally and in silico. In this study, we, for the first time, systematically analyzed the interactions of endostatin, a proteolytic fragment of collagen XVIII known to be anti-angiogenic and anti-tumoral, with heparin (HP) and representative heparan sulfate (HS) oligosaccharides of various lengths, sequences and sulfation patterns. We first used conventional molecular docking and a docking approach based on a repulsive scaling-replica exchange molecular dynamics technique, as well as unbiased molecular dynamic simulations, to obtain dynamically stable GAG binding poses. Then, the corresponding free energies of binding were calculated and the amino acid residues that contribute the most to GAG binding were identified. We also investigated the potential influence of Zn2+ on endostatin-HP complexes using computational approaches. These data provide new atomistic details of the molecular mechanism of HP's binding to endostatin, which will contribute to a better understanding of its interplay with proteoglycans at the cell surface and in the extracellular matrix.

Predictive value of procollagen c-protease enhancer protein on the prognosis of glioma patients

Procollagen c-protease enhancer protein (PCOLCE) performs an essential action in improving the recreation of procollagen c-protease and promoting the reconstruction of extracellular matrix. High PCOLCE expression was associated with a negative prognosis of stomach cancer, ovarian cancer, and osteosarcoma. The goal of this work is to investigate the function of PCOLCE in glioma. Multiple bioinformatics techniques have been employed to investigate the roles of PCOLCE in glioma, consisting of the correlation between PCOLCE and prognosis, immune checkpoints, immune cell infiltrates, and tumor microenvironment (TME). The gene ontology (GO) annotations and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used to assess the potential function of PCOLCE in glioma. PCOLCE was found to be increased in glioma. We revealed that PCOLCE was a potential prognostic factor and related to tumor grade. Up-regulated PCOLCE was related to poor prognosis in lower-grade glioma (LGG), glioblastoma multiforme (GBM), and recurrent glioma. PCOLCE was correlated with immune cell infiltration, particularly B cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells (DCs) in LGG, and DCs infiltration in GBM. PCOLCE was co-expressed with many genes related to the immune and the immune checkpoint. In addition, glioma patients with low expression of PCOLCE had a higher response to the immunological checkpoint blockade (ICB). Additionally, PCOLCE may exert its roles via several immune-related biological processes or pathways, such as leukocyte migration, activation of T cells, adaptive immune response, neutrophil-mediated immunity, NF-κB, and TNF signaling pathways. In conclusion, PCOLCE may be a new immune-related gene and regulate tumor development through immunological pathways.

High expression of PCOLCE gene indicate poor prognosis in patients and are associated with immune infiltration in glioma

The procollagen C-protease enhancer (PCOLCE) has been identified to influence tumor growth and metastasis in multiple cancers. However, the relationship between PCOLCE activity and the progression of gliomas remains largely unknown. Glioma RNA-seq data were derived from the Chinese Glioma Genome Atlas (CGGA) and The Cancer Genome Atlas databases for analysis. Kaplan-Meier survival curve, clinical characterization correlation, univariate and multivariate Cox, and receiver operating characteristic curve analyses were performed to assess the prognostic role of PCOLCE. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Gene Set Enrichment Analysis were used to determine the functions or pathways associated with PCOLCE. The ESTIMATE and CIBERSORT algorithms, Spearman's rank correlation analysis, and Tumor Immune Estimation Resource (TIMER) databases were used to explore the relationship between PCOLCE and immune infiltration. Correlation analysis between PCOLCE, related genes, and immune cell markers was conducted using the TIMER database. Immunophenoscore assays were performed to determine differential PCOLCE expression levels in glioma. The sensitivity of multi-drugs were determined to explore potential chemotherapeutic agents in between PCOLCE. Compared to normal brain tissue, PCOLCE expression was increased in glioma and correlated with shorter overall survival (OS). Furthermore, significant differences were observed in the immune scores and immune cell infiltration levels. PCOLCE is positively associated with immune checkpoints and many immune markers. Additionally, PCOLCE expression was higher in gliomas with higher IPS Z-scores in CGGA. High expression of PCOLCE increased sensitivity to multiple chemotherapy agents in CGGA (P < 0.001), and TCGA. These results suggest that PCOLCE significantly influences the prognosis of patients with glioma, can serve as an independent prognostic factor, and is related to tumor immunity. PCOLCE may be a novel immune-related target for treating gliomas. Additionally, analysis of chemosensitivity in gliomas with high PCOLCE expression may provide a promising direction for drug development.

Impact of calcium ions on the structural and dynamic properties of heparin oligosaccharides by computational analysis

Heparin (HP) belongs to glycosaminoglycans (GAGs), anionic linear polysaccharides composed of repetitive disaccharide units. They are key players in many biological processes occurring in the extracellular matrix and at the cell surface. GAGs are challenging molecules for computational research due to their high chemical heterogeneity, flexibility, periodicity, pseudosymmetry, predominantly electrostatics-driven nature of interactions with their protein partners and potential multipose binding. The molecular mechanisms underlying GAG interactions mediated by divalent ions, which are important for GAG binding to several proteins, are not well understood. The goal of this study was to characterize the binding of Ca²⁺ to two HP oligosaccharides of different lengths (dp10 and dp18, dp: degree of polymerization) and their impact on HP conformational space and their dynamic behavior with the use of molecular dynamics (MD)-based approaches with two Ca²⁺ parameter sets. MD data suggested that the flexibility of the monosaccharides, the glycosidic linkages and ring puckering were not affected by the presence of Ca²⁺, in contrast to H-bond propensities and the calculated R_g for a fraction of the oligosaccharide populations in both dp10 and dp18. Moreover, the essential differences in the data obtained by using two Ca²⁺ parameter sets were reported.

Topical heparin as an effective and safe treatment for patients with capecitabine-induced hand-foot syndrome: results of a phase IIA trial supported by proteomic profiling of skin biopsies

Background:

Hand-foot syndrome (HFS) is a common adverse reaction associated with capecitabine chemotherapy that significantly affects the quality of life of patients. This study evaluates the safety and effectiveness of a topical heparin (TH) treatment on the clinical manifestations and anatomopathological alterations of capecitabine-induced HFS. In addition, we performed proteome profiling of skin biopsies obtained from patients with HFS at baseline and after heparin treatment.

Methods:

Patients with grade ⩽ 2 HFS associated with capecitabine were included in this study. The primary end point was the effectiveness of TH in reducing HFS of any grade. Clinical improvement was evaluated by clinicians, and an improvement was perceived by patients who performed a weekly visual analog scale questionnaire. Secondary end points included a comparative histological analysis and protein expression in skin biopsies at baseline and after 3 weeks of HT treatment. Proteomic profiling was carried out using quantitative isobaric labelling and subsequently validated by a T-array.

Results:

Twenty-one patients were included in the study. The median TH treatment time was 7.6 weeks (range = 3.6–41.6 weeks), and the median response time was 3.01 weeks (95% CI = 2.15–3.97). At the end of treatment, 19 of 21 patients (90.48%) responded to treatment with a decrease in one or more grades of HFS. None of the patients experienced adverse effects related to TH usage, nor did they suspend chemotherapy treatment. The main findings observed in skin biopsies after treatment were a decrease in hyperkeratosis and lymphocytic infiltrates. The proteomic analysis showed altered expression of 34 proteins that were mainly related to wound healing, cell growth, and the immune response.

Conclusion:

Based on our results, topical heparin is an effective and safe treatment for clinical manifestations of HFS, probably due to the restauration of skin homeostasis after heparin treatment, as supported by our proteomics-derived data.

Trial registration:

EudraCT 2009-018171-13

Procollagen C-proteinase enhancer-1 (PCPE-1), a potential biomarker and therapeutic target for fibrosis

The correct balance between collagen synthesis and degradation is essential for almost every aspect of life, from development to healthy aging, reproduction and wound healing. When this balance is compromised by external or internal stress signals, it very often leads to disease as is the case in fibrotic conditions. Fibrosis occurs in the context of defective tissue repair and is characterized by the excessive, aberrant and debilitating deposition of fibril-forming collagens. Therefore, the numerous proteins involved in the biosynthesis of fibrillar collagens represent a potential and still underexploited source of therapeutic targets to prevent fibrosis. One such target is procollagen C-proteinase enhancer-1 (PCPE-1) which has the unique ability to accelerate procollagen maturation by BMP-1/tolloid-like proteinases (BTPs) and contributes to trigger collagen fibrillogenesis, without interfering with other BTP functions or the activities of other extracellular metalloproteinases. This role is achieved through a fine-tuned mechanism of action that is close to being elucidated and offers promising perspectives for drug design. Finally, the in vivo data accumulated in recent years also confirm that PCPE-1 overexpression is a general feature and early marker of fibrosis. In this review, we describe the results which presently support the driving role of PCPE-1 in fibrosis and discuss the questions that remain to be solved to validate its use as a biomarker or therapeutic target.

PCOLCE Is Potent Prognostic Biomarker and Associates With Immune Infiltration in Gastric Cancer

Background

The exact biological role of PCOLCE was not yet clear and there were few reports study the correlation of PCOLCE gene expression level with the occurrence and development of gastric cancer.

Methods

The expression of PCOLCE was analyzed by performing the Oncomine and Ualcan database. We evaluated the function of PCOLCE on clinical prognosis with the use of Kaplan-Meier plotter database. The relationship between PCOLCE and cancer immune in filtrates was researched by Tumor Immune Estimation Resource (TIMER) site database.

Results

PCOLCE significantly upregulated in gastric cancer patients compared to normal gastric samples. And the increased expression of PCOLCE mRNA was closely linked to shorter overall survival (OS), progress-free survival (PFS) in all gastric cancers. Besides, PCOLCE expression displayed a tight correlation with infiltrating levels of macrophages and dendritic cells (DCs) in gastric cancer. Moreover, PCOLCE expression was positively correlated with diverse immune marker sets in gastric cancer.

Conclusion

All the results above suggested that overexpression of PCOLCE indicated unfavorable prognosis in patients with gastric cancer. PCOLCE was correlated with immune infiltrating levels including those of B cells, CD8 + T cells, CD4 + T cells, macrophages, neutrophils, and DCs in gastric cancer patients. All the findings suggested that PCOLCE could be used as a prognostic biomarker for determining prognosis and immune infiltration in gastric cancer. Additionally, PCOLCE expression potentially contributed to the regulation of monocyte, M2 macrophage, Tfh, CD8 + T cell, TAM, Th1 cell Thus PCOLCE is a potential target for gastric cancer therapy and these preliminary findings require further study to determine whether PCOLCE-targeting reagents might be developed for clinical application in gastric cancer.

Analysis of Procollagen C-Proteinase Enhancer-1/Glycosaminoglycan Binding Sites and of the Potential Role of Calcium Ions in the Interaction

In this study, we characterize the interactions between the extracellular matrix protein, procollagen C-proteinase enhancer-1 (PCPE-1), and glycosaminoglycans (GAGs), which are linear anionic periodic polysaccharides. We applied molecular modeling approaches to build a structural model of full-length PCPE-1, which is not experimentally available, to predict GAG binding poses for various GAG lengths, types and sulfation patterns, and to determine the effect of calcium ions on the binding. The computational data are analyzed and discussed in the context of the experimental results previously obtained using surface plasmon resonance binding assays. We also provide experimental data on PCPE-1/GAG interactions obtained using inhibition assays with GAG oligosaccharides ranging from disaccharides to octadecasaccharides. Our results predict the localization of GAG-binding sites at the amino acid residue level onto PCPE-1 and is the first attempt to describe the effects of ions on protein-GAG binding using modeling approaches. In addition, this study allows us to get deeper insights into the in silico methodology challenges and limitations when applied to GAG-protein interactions.

Up-regulation of PCOLCE by TWIST1 promotes metastasis in Osteosarcoma

Procollagen C-proteinase enhancer protein (PCOLCE) was originally identified as an enhancer to facilitate the catalysis of procollagens by BMP1. PCOLCE participates in the reconstitution of extracellular and corneal repair. The elevation of PCOLCE in blood indicates that breast cancer has metastasized into the bones. However, direct research on PCOLCE has not been reported.

Methods: ECM candidates were identified by RNA-seq analysis from 4 normal and 16 osteosarcoma tissues. The in vitro migration and invasion abilities of osteosarcoma cells were determined by a Transwell assay. A spontaneous metastatic osteosarcoma model was established to assess osteosarcoma metastasis in vivo. The N-linked glycosylated amino acids were identified by PNGase F treatment combined with Western blotting. The mechanism of TWIST1 regulating PCOLCE transcription was elucidated by luciferase, qPCR and ChIP assays.

Results: PCOLCE was markedly up-regulated in human osteosarcoma tissues compared to its expression in noncancerous adjacent tissues; high PCOLCE expression in tissues correlated with a poor patient prognosis, and the knockdown of PCOLCE by shRNAs impaired the migration, invasion and lung metastasis of osteosarcoma cells. The overexpression of wild-type PCOLCE, but not its N29Q mutant, promoted migration, invasion and metastasis, indicating that the glycosylation of PCOLCE at Asn29 is necessary for its functions in osteosarcoma. TWIST1, a key transcription factor in metastasis, was also overexpressed in osteosarcoma tissues and positively correlated with either PCOLCE or its potential procollagen substrates, such as COL1A1, COL1A2, COL5A1, COL8A2 and COL10A1.

Conclusion: Our findings are the first to provide evidence that PCOLCE plays a critical role in promoting the lung metastasis of osteosarcoma, and this up-regulation of PCOLCE by TWIST1 may lead to a new therapeutic strategy to treat patients with metastatic osteosarcoma.

Evaluation of serum procollagen C-proteinase enhancer 1 level as a fibrosis marker in patients with chronic hepatitis B

AIM

Although liver biopsy has long been considered the gold standard for staging fibrosis, because of the disadvantages and risks of biopsy, several noninvasive processes such as serum biomarkers have been introduced for the assessment of liver fibrosis. The aim of this study was to assess the diagnostic value of serum procollagen C-proteinase enhancer 1 (PCPE-1) as a noninvasive fibrosis marker in treatment-naive chronic hepatitis B patients.

PATIENTS AND METHODS

This study included 126 patients with biopsy-proven hepatitis B and 50 healthy controls. Fibrosis stage was determined using the Ishak scoring system. The PCPE-1 level was measured using the enzyme-linked immunosorbent assay assay, and the aspartate aminotransferase to platelet ratio index and the FIB-4 index were calculated using the formulas described in Appendix 1 (Supplemental digital content 1, http://links.lww.com/EJGH/A277).

RESULTS

Serum PCPE-1 levels of chronic hepatitis B patients were found to be significantly lower than those of the healthy control group (4.49±2.74 vs. 42.9±59.6 pg/ml, respectively, P<0.001). There was a statistically significant negative correlation between serum PCPE-1 level and fibrosis stage (P=0.011; r=-0.226). A statistically significant negative correlation was found between serum PCPE-1 level and necroinflammatory activity (P=0.030; r=-0.194). PCPE-1 levels of patients with liver fibrosis scores of F1-2 were statistically significantly lower than those of the healthy control group (P<0.001) (area under the receiver operating characteristic: 0.955). The area under the receiver operating characteristic of the PCPE-1 level was 0.615 for the prediction of fibrosis (F0 vs. F1-6) (P=0.039).

CONCLUSION

Serum PCPE-1 might be used as a noninvasive marker of liver fibrosis. Further animal and human studies are needed to assess the utility of this marker.

The Multimerization State of the Amyloid-β42 Amyloid Peptide Governs its Interaction Network with the Extracellular Matrix

The goals of this work were i) to identify the interactions of amyloid-β (Aβ)42 under monomeric, oligomeric, and fibrillar forms with the extracellular matrix (ECM) and receptors, ii) to determine the influence of Aβ42 supramolecular organization on these interactions, and iii) to identify the molecular functions, biological processes, and pathways targeted by Aβ42 in the ECM. The ECM and cell surface partners of Aβ42 and its supramolecular forms were identified with protein and glycosaminoglycan (GAG) arrays (81 molecules in triplicate) probed by surface plasmon resonance imaging. The number of partners of Aβ42 increased upon its multimerization, ranging from 4 for the peptide up to 53 for the fibrillar aggregates. The peptide interacted only with ECM proteins but their percentage among Aβ42 partners decreased upon multimerization. Aβ42 and its supramolecular forms recognized different molecular features on their partners, and the partners of Aβ42 fibrillar forms were enriched in laminin IV-A, N-terminal, and EGF-like domains. Aβ42 oligomerization triggered interactions with receptors, whereas Aβ42 fibrillogenesis promoted binding to GAGs, proteoglycans, enzymes, and growth factors and the ability to interact with perineuronal nets. Fibril aggregation bind to further membrane proteins including tumor endothelial marker-8, syndecan-4, and discoidin-domain receptor-2. The partners of the Aβ42 supramolecular forms are enriched in proteins contributing to cell growth and/or maintenance, involved in integrin cell surface interactions and expressed in kidney cancer, preadipocytes, and dentin. In conclusion, the supramolecular assembly of Aβ42 governs its ability to interact in vitro with ECM proteins, remodeling and crosslinking ECM enzymes, proteoglycans, and receptors.

Glycosaminoglycanomics: where we are

Glycosaminoglycans regulate numerous physiopathological processes such as development, angiogenesis, innate immunity, cancer and neurodegenerative diseases. Cell surface GAGs are involved in cell-cell and cell-matrix interactions, cell adhesion and signaling, and host-pathogen interactions. GAGs contribute to the assembly of the extracellular matrix and heparan sulfate chains are able to sequester growth factors in the ECM. Their biological activities are regulated by their interactions with proteins. The structural heterogeneity of GAGs, mostly due to chemical modifications occurring during and after their synthesis, makes the development of analytical techniques for their profiling in cells, tissues, and biological fluids, and of computational tools for mining GAG-protein interaction data very challenging. We give here an overview of the experimental approaches used in glycosaminoglycomics, of the major GAG-protein interactomes characterized so far, and of the computational tools and databases available to analyze and store GAG structures and interactions.

Data comparing the kinetics of procollagen type I processing by bone morphogenetic protein 1 (BMP-1) with and without procollagen C-proteinase enhancer 1 (PCPE-1)

This article provides kinetic constants for C-terminal processing of procollagen type I by bone morphogenetic protein 1 (BMP-1; the major procollagen C-proteinase), a reaction stimulated by the connective tissue glycoprotein procollagen C-proteinase enhancer 1 (PCPE-1). Reported are K_m, V_max, K_cat and K_cat/K_m (catalytic coefficient) values for BMP-1 alone, BMP-1 with intact PCPE-1, BMP-1 with the CUB (Complement C1r/C1s, Uegf, BMP-1) domains fragment of PCPE-1 as well as its NTR (netrin-like) domain.

Procollagen C-Proteinase Enhancer 1 (PCPE-1) as a Plasma Marker of Muscle and Liver Fibrosis in Mice

Current non-invasive diagnostic methods of fibrosis are limited in their ability to identify early and intermediate stages of fibrosis and assess the efficacy of therapy. New biomarkers of fibrosis are therefore constantly sought for, leading us to evaluate procollagen C-proteinase enhancer 1 (PCPE-1), a fibrosis-related extracellular matrix glycoprotein, as a plasma marker of fibrosis. A sandwich ELISA that permitted accurate measurements of PCPE-1 concentrations in mouse plasma was established. Tissue fibrosis was assessed using histochemical, immunofluorescence, and immunoblotting analyses for type I collagen and PCPE-1. The normal plasma concentration of PCPE-1 in 6 weeks to 4 months old mice was ~200 ng/ml (189.5 ± 11.3 to 206.8 ± 13.8 ng/ml). PCPE-1 plasma concentrations in four and 8.5 months old mdx mice displaying fibrotic diaphragms increased 27 and 40% respectively relatively to age-matched control mice, an increase comparable to that of the N-propeptide of procollagen type III (PIIINP), a known blood marker of fibrosis. PCPE-1 plasma levels in mice with CCl4-induced liver fibrosis increased 34 to 50% relatively to respective controls and reflected the severity of the disease, namely increased gradually during the progression of fibrosis and went down to basal levels during recovery, in parallel to changes in the liver content of collagen I and PCPE-1. The results favor PCPE-1 as a potential new clinically valuable fibrosis biomarker.

Proteases decode the extracellular matrix cryptome

The extracellular matrix is comprised of 1100 core-matrisome and matrisome-associated proteins and of glycosaminoglycans. This structural scaffold contributes to the organization and mechanical properties of tissues and modulates cell behavior. The extracellular matrix is dynamic and undergoes constant remodeling, which leads to diseases if uncontrolled. Bioactive fragments, called matricryptins, are released from the extracellular proteins by limited proteolysis and have biological activities on their own. They regulate numerous physiological and pathological processes such as angiogenesis, cancer, diabetes, wound healing, fibrosis and infectious diseases and either improve or worsen the course of diseases depending on the matricryptins and on the molecular and biological contexts. Several protease families release matricryptins from core-matrisome and matrisome-associated proteins both in vitro and in vivo. The major proteases, which decrypt the extracellular matrix, are zinc metalloproteinases of the metzincin superfamily (matrixins, adamalysins and astacins), cysteine proteinases and serine proteases. Some matricryptins act as enzyme inhibitors, further connecting protease and matricryptin fates and providing intricate regulation of major physiopathological processes such as angiogenesis and tumorigenesis. They strengthen the role of the extracellular matrix as a key player in tissue failure and core-matrisome and matrisome-associated proteins as important therapeutic targets.

Loss of fibulin-4 disrupts collagen synthesis and maturation: implications for pathology resulting from EFEMP2 mutations

Homozygous recessive mutations in either EFEMP2 (encoding fibulin-4) or FBLN5 (encoding fibulin-5), critical genes for elastogenesis, lead to autosomal recessive cutis laxa types 1B and 1A, respectively. Previously, fibulin-4 was shown to bind lysyl oxidase (LOX), an elastin/collagen cross-linking enzyme, in vitro. Consistently, reported defects in humans with EFEMP2 mutations are more severe and broad in range than those due to FBLN5 mutations and encompass both elastin-rich and collagen-rich tissues. However, the underlying disease mechanism in EFEMP2 mutations has not been fully addressed. Here, we show that fibulin-4 is important for the integrity of aortic collagen in addition to elastin. Smooth muscle-specific Efemp2 loss in mouse (termed SMKO) resulted in altered fibrillar collagen localization with larger, poorly organized fibrils. LOX activity was decreased in Efemp2-null cells, and collagen cross-linking was diminished in SMKO aortas; however, elastin cross-linking was unaffected and the level of mature LOX was maintained to that of wild-type aortas. Proteomic screening identified multiple proteins involved in procollagen processing and maturation as potential fibulin-4-binding partners. We showed that fibulin-4 binds procollagen C-endopeptidase enhancer 1 (Pcolce), which enhances proteolytic cleavage of the procollagen C-terminal propeptide during procollagen processing. Interestingly, however, procollagen cleavage was not affected by the presence or absence of fibulin-4 in vitro. Thus, our data indicate that fibulin-4 serves as a potential scaffolding protein during collagen maturation in the extracellular space. Analysis of collagen in other tissues affected by fibulin-4 loss should further increase our understanding of underlying pathologic mechanisms in patients with EFEMP2 mutations.

Secreted Frizzled-related protein 3 (sFRP3)-mediated suppression of interleukin-6 receptor release by A disintegrin and metalloprotease 17 (ADAM17) is abrogated in the osteoarthritis-associated rare double variant of sFRP3

A disintegrin and metalloprotease 17 (ADAM17) activity and secreted Frizzled-related protein 3 (sFRP3) down-regulation or expression of its rare double variant is associated with arthritis. sFRP3 interacts with interleukin-6 receptor (IL-6R) and ADAM17 and suppresses ADAM17 activity, whereas the rare variant does not; these findings provide explanation for their opposing pathogenic associations.

Procollagen C-endopeptidase Enhancer Protein 2 (PCPE2) Reduces Atherosclerosis in Mice by Enhancing Scavenger Receptor Class B1 (SR-BI)-mediated High-density Lipoprotein (HDL)-Cholesteryl Ester Uptake

Studies in human populations have shown a significant correlation between procollagen C-endopeptidase enhancer protein 2 (PCPE2) single nucleotide polymorphisms and plasma HDL cholesterol concentrations. PCPE2, a 52-kDa glycoprotein located in the extracellular matrix, enhances the cleavage of C-terminal procollagen by bone morphogenetic protein 1 (BMP1). Our studies here focused on investigating the basis for the elevated concentration of enlarged plasma HDL in PCPE2-deficient mice to determine whether they protected against diet-induced atherosclerosis. PCPE2-deficient mice were crossed with LDL receptor-deficient mice to obtain LDLr(-/-), PCPE2(-/-) mice, which had elevated HDL levels compared with LDLr(-/-) mice with similar LDL concentrations. We found that LDLr(-/-), PCPE2(-/-) mice had significantly more neutral lipid and CD68+ infiltration in the aortic root than LDLr(-/-) mice. Surprisingly, in light of their elevated HDL levels, the extent of aortic lipid deposition in LDLr(-/-), PCPE2(-/-) mice was similar to that reported for LDLr(-/-), apoA-I(-/-) mice, which lack any apoA-I/HDL. Furthermore, LDLr(-/-), PCPE2(-/-) mice had reduced HDL apoA-I fractional clearance and macrophage to fecal reverse cholesterol transport rates compared with LDLr(-/-) mice, despite a 2-fold increase in liver SR-BI expression. PCPE2 was shown to enhance SR-BI function by increasing the rate of HDL-associated cholesteryl ester uptake, possibly by optimizing SR-BI localization and/or conformation. We conclude that PCPE2 is atheroprotective and an important component of the reverse cholesterol transport HDL system.

The NTR domain of procollagen C-proteinase enhancer-1 (PCPE-1) mediates PCPE-1 binding to syndecans-1, -2 and -4 as well as fibronectin

Procollagen C-proteinase enhancer 1 (PCPE-1) is an extracellular matrix glycoprotein that can stimulate procollagen processing by procollagen C-proteinases (PCPs) such as bone morphogenetic protein-1 (BMP-1). PCPE-1 consists of two CUB domains that bind to the procollagen C-propeptide and are responsible for enhancing activity and a netrin-like (NTR) domain that binds to BMP-1 as well as heparin and heparan sulfate. The NTR domain also mediates binding of PCPE-1 to cells, an interaction inhibited by heparin, thus suggesting involvement of cell membrane heparan-sulfate proteoglycans (HSPGs). Using pull-down experiments and an ELISA type binding assay we show here that PCPE-1 binds to three cell membrane HSPGs, syndecans-1, -2 and -4. We also demonstrate that this binding is mediated by the NTR domain and depends on the glycosaminoglycan chains of the syndecans. Using co-immunoprecipitation and an ELISA type binding assay we show that PCPE-1 can also bind fibronectin (an established binding partner of BMP-1), another interaction involving the NTR domain. Consistently, fibronectin inhibits cell attachment to PCPE-1 although it does not affect PCPE-1 enhancing activity. PCPE-1 is not an adhesive protein since cell attachment to PCPE-1 is not associated with cell spreading and/or actin filaments formation. The results suggest that PCPE-1 binding to syndecans and/or fibronectin may control collagen fibril assembly on the cell surface. Further characterization of these interactions may pave the way for future design of new means to modulate collagen deposition in pathological conditions such as fibrosis.

Extended interaction network of procollagen C-proteinase enhancer-1 in the extracellular matrix

PCPE-1 (procollagen C-proteinase enhancer-1) is an extracellular matrix glycoprotein that can stimulate procollagen processing by procollagen C-proteinases such as BMP-1 (bone morphogenetic protein 1). PCPE-1 interacts with several proteins in addition to procollagens and BMP-1, suggesting that it could be involved in biological processes other than collagen maturation. We thus searched for additional partners of PCPE-1 in the extracellular matrix, which could provide new insights into its biological roles. We identified 17 new partners of PCPE-1 by SPR (surface plasmon resonance) imaging. PCPE-1 forms a transient complex with the β-amyloid peptide, whereas it forms high or very high affinity complexes with laminin-111 (KD=58.8 pM), collagen VI (KD=9.5 nM), TSP-1 (thrombospondin-1) (KD1=19.9 pM, KD2=14.5 nM), collagen IV (KD=49.4 nM) and endostatin, a fragment of collagen XVIII (KD1=0.30 nM, KD2=1.1 nM). Endostatin binds to the NTR (netrin-like) domain of PCPE-1 and decreases the degree of superstimulation of PCPE-1 enhancing activity by heparin. The analysis of the PCPE-1 interaction network based on Gene Ontology terms suggests that, besides its role in collagen deposition, PCPE-1 might be involved in tumour growth, neurodegenerative diseases and angiogenesis. In vitro assays have indeed shown that the CUB1CUB2 (where CUB is complement protein subcomponents C1r/C1s, urchin embryonic growth factor and BMP-1) fragment of PCPE-1 inhibits angiogenesis.

Application of layer-by-layer coatings to tissue scaffolds – development of an angiogenic biomaterial

Development of flexible coating strategies to promote angiogenesis is critical to effectively treat chronic, non-healing wounds.

Heparin-protein interactions: from affinity and kinetics to biological roles. Application to an interaction network regulating angiogenesis

Numerous extracellular proteins, growth factors, chemokines, cytokines, enzymes, lipoproteins, involved in a variety of biological processes, interact with heparin and/or heparan sulfate at the cell surface and in the extracellular matrix (ECM). The goal of this study is to investigate the relationship(s) between affinity and kinetics of heparin-protein interactions and the localization of the proteins, their intrinsic disorder and their biological roles. Most proteins bind to heparin with a higher affinity than their fragments and form more stable complexes with heparin than with heparan sulfate. Lipoproteins and matrisome-associated proteins (e.g. growth factors and cytokines) bind to heparin with very high affinity. Matrisome-associated proteins form transient complexes with heparin. However they bind to this glycosaminoglycan with a higher affinity than the proteins of the core matrisome, which contribute to ECM assembly and organization, and than the secreted proteins which are not associated with the ECM. The association rate of proteins with heparin is related to the intrinsic disorder of heparin-binding sites. Enzyme inhibitor activity, protein dimerization, skeletal system development and pathways in cancer are functionally associated with proteins displaying a high or very high affinity for heparin (KD<100 nM). Besides their use in investigating molecular recognition and functions, kinetics and affinity are essential to prioritize interactions in networks and to build network models as discussed for the interaction network established at the surface of endothelial cells by endostatin, a heparin-binding protein regulating angiogenesis.

A disintegrin-like and metalloprotease domain containing thrombospondin type 1 motif-like 5 (ADAMTSL5) is a novel fibrillin-1-, fibrillin-2-, and heparin-binding member of the ADAMTS superfamily containing a netrin-like module

ADAMTS-like proteins are related to ADAMTS metalloproteases by their similarity to ADAMTS ancillary domains. Here, we have characterized ADAMTSL5, a novel member of the superfamily with a unique modular organization that includes a single C-terminal netrin-like (NTR) module. Alternative splicing of ADAMTSL5 at its 5' end generates two transcripts that encode different signal peptides, but the same mature protein. These transcripts differ in their translational efficiency. Recombinant ADAMTSL5 is a secreted, N-glycosylated 60kDa glycoprotein located in the subcellular matrix, on the cell-surface, and in the medium of transfected cells. RT-PCR and western blot analysis of adult mouse tissues showed broad expression. Western blot analysis suggested proteolytic release of the NTR module in transfected cells as well as in some mouse tissues. Immunostaining during mouse organogenesis identified ADAMTSL5 in musculoskeletal tissues such as skeletal muscle, cartilage and bone, as well as in many epithelia. Affinity-chromatography demonstrated heparin-binding of ADAMTSL5 through its NTR-module. Recombinant ADAMTSL5 bound to both fibrillin-1 and fibrillin-2, and co-localized with fibrillin microfibrils in the extracellular matrix of cultured fibroblasts, but without discernible effect on microfibril assembly. ADAMTSL5 is the first family member shown to bind both fibrillin-1 and fibrillin-2. Like other ADAMTS proteins implicated in microfibril biology through identification of human and animal mutations, ADAMTSL5 could have a role in modulating microfibril functions.

Single-cycle kinetic analysis of ternary DNA complexes by surface plasmon resonance on a decaying surface

Complexes involving three DNA strands were used to demonstrate that the single-cycle kinetics (SCK) method, which consists in injecting sequentially samples at increasing concentrations and until now used exclusively to investigate bimolecular complexes by surface plasmon resonance, can be extended to the kinetic analysis of ternary complexes. DNA targets, B, were designed with sequences of variable lengths on their 3' sides that recognise a surface-immobilized biotinylated DNA anchor, A. These targets displayed on their 5' sides sequences that recognise DNA oligonucleotides of variable lengths, C, namely the analytes. Combinations of B and C DNA oligonucleotides on A generated ternary complexes each composed of two Watson-Crick helices displaying different kinetic properties. The target-analyte B-C duplexes were formed by sequentially injecting three increasing concentrations of the analytes C during the dissociation phase of the target B from the anchor A. The sensorgrams for the target-analyte complexes dissociating from the functionalized surface were successfully fitted by the SCK method while the target dissociated from the anchor, i.e. on a decaying surface. Within the range of applicability of the method which is driven by the rate of dissociation of the target from the anchor, the rate and equilibrium constants characteristic of these target-analyte duplexes of the ternary complexes did not depend on how fast the targets dissociated from the immobilized DNA anchor. In addition the results agreed very well with those obtained when such duplexes were analysed directly as bimolecular complexes, i.e. when the target, modified with a biotin, was directly immobilized onto a streptavidin sensor chip surface rather than captured by an anchor. Therefore the method we named SCKODS (Single-Cycle Kinetics On a Decaying Surface) can also be used to investigate complexes formed during a dissociation phase, in a ternary complex context. The SCKODS method can be combined with the SCK one to fully characterize the two bimolecular complexes of a ternary complex.

Metalloproteinases in Drosophila to humans that are central players in developmental processes

Many secreted proteins are synthesized as precursors with propeptides that must be cleaved to yield the mature functional form of the molecule. In addition, various growth factors occur in extracellular latent complexes with protein antagonists and are activated upon cleavage of such antagonists. Research in the separate fields of embryonic patterning and extracellular matrix formation has identified members of the BMP1/Tolloid-like family of metalloproteinases as key players in these types of biosynthetic processing events in species ranging from Drosophila to humans.

Disruption of the murine procollagen C-proteinase enhancer 2 gene causes accumulation of pro-apoA-I and increased HDL levels

Given the increased prevalence of cardiovascular disease in the world, the search for genetic variations that impact risk factors associated with the development of this disease continues. Multiple genetic association studies demonstrate that procollagen C-proteinase enhancer 2 (PCPE2) modulates HDL levels. Recent studies revealed an unexpected role for this protein in the proteolytic processing of pro-apolipoprotein (apo) A-I by enhancing the cleavage of the hexapeptide extension present at the N-terminus of apoA-I. To investigate the role of the PCPE2 protein in an in vivo model, PCPE2-deficient (PCPE2 KO) mice were examined, and a detailed characterization of plasma lipid profiles, apoA-I, HDL speciation, and function was done. Results of isoelectric focusing (IEF) electrophoresis together with the identification of the amino terminal peptides DEPQSQWDK and WHVWQQDEPQSQWDVK, representing mature apoA-I and pro-apoA-I, respectively, in serum from PCPE2 KO mice confirmed that PCPE2 has a role in apoA-I maturation. Lipid profiles showed a marked increase in plasma apoA-I and HDL-cholesterol (HDL-C) levels in PCPE2 KO mice compared with wild-type littermates, regardless of gender or diet. Changes in HDL particle size and electrophoretic mobility observed in PCPE2 KO mice suggest that the presence of pro-apoA-I impairs the maturation of HDL. ABCA1-dependent cholesterol efflux is defective in PCPE2 KO mice, suggesting that the functionality of HDL is altered.