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 ß-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.

Matricryptins and matrikines: biologically active fragments of the extracellular matrix.

Numerous extracellular proteins and glycosaminoglycans (GAGs) undergo limited enzymatic cleavage resulting in the release of fragments exerting biological activities, which are usually different from those of the full-length molecules. In this review, we define matrikines and matricryptins, which are bioactive fragments released from the extracellular matrix proteins, proteoglycans and GAGs and report their major biological activities. These fragments regulate a number of physiopathological processes including angiogenesis, cancer, fibrosis, inflammation, neurodegenerative diseases and wound healing. The challenges to translate these fragments from molecules biologically active in vitro and in experimental models to potential drugs are discussed in the last part of the review.

The Interactome of Cancer-Related Lysyl Oxidase and Lysyl Oxidase-Like Proteins.

The members of the lysyl oxidase (LOX) family are amine oxidases, which initiate the covalent cross-linking of the extracellular matrix (ECM), regulate ECM stiffness, and contribute to cancer progression. The aim of this study was to build the first draft of the interactome of the five members of the LOX family in order to determine its molecular functions, the biological and signaling pathways mediating these functions, the biological processes it is involved in, and if and how it is rewired in cancer. In vitro binding assays, based on surface plasmon resonance and bio-layer interferometry, combined with queries of interaction databases and interaction datasets, were used to retrieve interaction data. The interactome was then analyzed using computational tools. We identified 31 new interactions and 14 new partners of LOXL2, including the α5ß1 integrin, and built an interactome comprising 320 proteins, 5 glycosaminoglycans, and 399 interactions. This network participates in ECM organization, degradation and cross-linking, cell-ECM interactions mediated by non-integrin and integrin receptors, protein folding and chaperone activity, organ and blood vessel development, cellular response to stress, and signal transduction. We showed that this network is rewired in colorectal carcinoma, leading to a switch from ECM organization to protein folding and chaperone activity.

Scavenger Receptor Cysteine-Rich domains of Lysyl Oxidase-Like2 regulate endothelial ECM and angiogenesis through non-catalytic scaffolding mechanisms.

Lysyl oxidases are major actors of microenvironment and extracellular matrix (ECM) remodeling. These cross-linking enzymes are thus involved in many aspects of physiopathology, including tumor progression, fibrosis and cardiovascular diseases. We have already shown that Lysyl Oxidase-Like 2 (LOXL2) regulates collagen IV deposition by endothelial cells and angiogenesis. We here provide evidence that LOXL2 also affects deposition of other ECM components, including fibronectin, thus altering structural and mechanical properties of the matrix generated by endothelial cells. LOXL2 interacts intracellularly and directly with collagen IV and fibronectin before incorporation into ECM fibrillar structures upon exocytosis, as demonstrated by TIRF time-lapse microscopy. Furthermore, surface plasmon resonance experiments using recombinant scavenger receptor cysteine-rich (SRCR) domains truncated for the catalytic domain demonstrated their direct binding to collagen IV. We thus used directed mutagenesis to investigate the role of LOXL2 catalytic domain. Neither enzyme activity nor catalytic domain were necessary for collagen IV deposition and angiogenesis, whereas the SRCR domains were effective for these processes. Finally, surface coating with recombinant SRCR domains restored deposition of collagen IV by LOXL2-depleted cells. We thus propose that LOXL2 SRCR domains orchestrate scaffolding of the vascular basement membrane and angiogenesis through interactions with collagen IV and fibronectin, independently of the enzymatic cross-linking activity.

A comparative analysis of secreted protein disulfide isomerases from the tropical co-endemic parasites Schistosoma mansoni and Leishmania major.

The human parasites Schistosoma mansoni and Leishmania major are co-endemic and a major threat to human health. Though displaying different tissue tropisms, they excrete/secrete similar subsets of intracellular proteins that, interacting with the host extracellular matrix (ECM), help the parasites invading the host. We selected one of the most abundant proteins found in the secretomes of both parasites, protein disulfide isomerase (PDI), and performed a comparative screening with surface plasmon resonance imaging (SPRi), looking for ECM binding partners. Both PDIs bind heparan sulfate; none of them binds collagens; each of them binds further ECM components, possibly linked to the different tropisms. We investigated by small-angle X-ray scattering both PDIs structures and those of a few complexes with host partners, in order to better understand the differences within this conserved family fold. Furthermore, we highlighted a previously undisclosed moonlighting behaviour of both PDIs, namely a concentration-dependent switch of function from thiol-oxidoreductase to holdase. Finally, we have tried to exploit the differences to look for possible compounds able to interfere with the redox activity of both PDI.

The Multimerization State of the Amyloid-ß42 Amyloid Peptide Governs its Interaction Network with the Extracellular Matrix.

The goals of this work were i) to identify the interactions of amyloid-ß (Aß)42 under monomeric, oligomeric, and fibrillar forms with the extracellular matrix (ECM) and receptors, ii) to determine the influence of Aß42 supramolecular organization on these interactions, and iii) to identify the molecular functions, biological processes, and pathways targeted by Aß42 in the ECM. The ECM and cell surface partners of Aß42 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 Aß42 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 Aß42 partners decreased upon multimerization. Aß42 and its supramolecular forms recognized different molecular features on their partners, and the partners of Aß42 fibrillar forms were enriched in laminin IV-A, N-terminal, and EGF-like domains. Aß42 oligomerization triggered interactions with receptors, whereas Aß42 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 Aß42 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 Aß42 governs its ability to interact in vitro with ECM proteins, remodeling and crosslinking ECM enzymes, proteoglycans, and receptors.

Endostatin level in cerebrospinal fluid of patients with Alzheimer's disease.

The aim of this study was to measure the level of endostatin, a fragment of collagen XVIII that accumulates in the brain of patients with Alzheimer's disease (AD), in the cerebrospinal fluids (CSF) of patients with neurodegenerative diseases. The concentrations of total protein, endostatin, amyloid-ß1-42 peptide, tau, and hyperphosphorylated tau proteins were measured by enzyme-linked immunosorbent assay in CSF of patients with AD (n = 57), behavioral frontotemporal dementia (bvFTD, n = 22), non AD and non FTD dementia (nAD/nFTD, n = 84), and 45 subjects without neurodegenerative diseases. The statistical significance of the results was assessed by Mann-Whitney and Kruskal and Wallis tests, and by ROC analysis. The concentration of endostatin in CSF was higher than the levels of the three markers of AD both in control subjects and in patients with neurodegenerative diseases. The endostatin/amyloid-ß1-42 ratio was significantly increased in patients with AD (257%, p < 0.0001) and nAD/nFTD (140%, p < 0.0001) compared to controls. The endostatin/tau protein ratio was significantly decreased in patients with AD (-49%, p < 0.0001) but was increased in bvFTD patients (89%, p < 0.0001) compared to controls. In the same way, the endostatin/hyperphosphorylated tau protein ratio was decreased in patients with AD (-21%, p = 0.0002) but increased in patients with bvFTD (81%, p = 0.0026), compared to controls. The measurement of endostatin in CSF and the calculation of its ratio relative to well-established AD markers improve the diagnosis of bvFTD patients and the discrimination of patients with AD from those with bvFTD and nAD/nFTD.