Constitutive Release of α4 Type V Collagen N-terminal Domain by Schwann Cells and Binding to Cell Surface and Extracellular Matrix Heparan Sulfate Proteoglycans

Quercetin-derived carbon dots promote proliferation and migration of Schwann cells and enhance neurite outgrowth

Quercetin, a flavonoid known for its antioxidant properties, has recently garnered attention as a potential neuroprotective agent for treatment of the injured nervous system. The repair of peripheral nerve injuries hinges on the proliferation and migration of Schwann cells, which play a crucial role in supporting axonal growth and myelination. In this study we synthesized Quercetin-derived carbon dots (QCDs) and investigated their effects on cultured Schwann cells and the NG108-15 cell line. QCDs was obtained by solvothermal synthesis and characterized via UV-vis absorption spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The particles demonstrated significant dose-dependent free radical scavenging activity in DPPH and ABTS radical scavenging assays, supported in vitro proliferation and migration of Schwann cells, expression of neurotrophic and angiogenic growth factors, and stimulated neurite outgrowth from NG108-15 cells. Thus, QCDs could serve as a potential novel treatment strategy to promote regeneration in the injured peripheral nervous system.

Generation of pure cultures of autologous Schwann cells by use of biopsy specimens of the dorsal cutaneous branches of the cervical nerves of young adult dogs

OBJECTIVE To identify an optimal technique for isolation, purification, and amplification of Schwann cells (SCs) from biopsy specimens of the dorsal cutaneous branches of the cervical nerves of dogs. SAMPLE Biopsy specimens of dorsal cervical cutaneous nerves from the cadavers of three 1- to 2-year-old dogs. PROCEDURES Nerve specimens were dissected, predegenerated, and dissociated to isolate single cells. After culture to enhance SC growth, cells were immunopurified by use of magnetic beads. Cell purity was evaluated by assessing expression of cell surface antigens p75 (to detect SCs) and CD90 (to detect fibroblasts). Effects of various concentrations of recombinant human glial growth factor 2 (rhGGF2) on SC proliferation were tested. Cell doubling time was assessed in SC cultures with selected concentrations of rhGGF2. RESULTS Mean ± SD wet weight of nerve fascicles obtained from the biopsy specimens was 16.8 ± 2.8 mg. A mean predegeneration period of 8.6 days yielded approximately 6,000 cells/mg of nerve tissue, and primary culture yielded 43,000 cells/mg of nerve tissue in a mean of 11 days, of which 39.9 ± 9.1% expressed p75. Immunopurification with magnetic beads yielded a mean of 85.4 ± 1.9% p75-positive cells. Two passages of subculture with 10μM cytosine arabinoside further enhanced SC purity to a mean of 97.8 ± 1.2% p75-positive cells. Finally, rhGGF2 supplementation at a range of 40 to 100 ng/mL increased the SC proliferation rate up to 3-fold. CONCLUSIONS AND CLINICAL RELEVANCE SCs could be cultured from biopsy specimens of dorsal cervical cutaneous nerves and purified and expanded to generate adequate numbers for autologous transplants to treat dogs with spinal cord and peripheral nerve injuries.

Fell-Muir Lecture: Heparan sulphate and the art of cell regulation: a polymer chain conducts the protein orchestra

Heparan sulphate (HS) sits at the interface of the cell and the extracellular matrix. It is a member of the glycosaminoglycan family of anionic polysaccharides with unique structural features designed for protein interaction and regulation. Its client proteins include soluble effectors (e.g. growth factors, morphogens, chemokines), membrane receptors and cell adhesion proteins such as fibronectin, fibrillin and various types of collagen. The protein-binding properties of HS, together with its strategic positioning in the pericellular domain, are indicative of key roles in mediating the flow of regulatory signals between cells and their microenvironment. The control of transmembrane signalling is a fundamental element in the complex biology of HS. It seems likely that, in some way, HS orchestrates diverse signalling pathways to facilitate information processing inside the cell. A dictionary definition of an orchestra is 'a large group of musicians who play together on various instruments …' to paraphrase, the HS orchestra is 'a large group of proteins that play together on various receptors'. HS conducts this orchestra to ensure that proteins hit the right notes on their receptors but, in the manner of a true conductor, does it also set 'the musical pulse' and create rhythm and harmony attractive to the cell? This is too big a question to answer but fun to think about as you read this review.

The Role of Collagens in Peripheral Nerve Myelination and Function

In the peripheral nervous system, myelin is formed by Schwann cells, which are surrounded by a basal lamina. Extracellular matrix (ECM) molecules in the basal lamina play an important role in regulating Schwann cell functions, including adhesion, survival, spreading, and myelination, as well as in supporting neurite outgrowth. Collagens are a major component of ECM molecules, which include 28 types that differ in structure and function. A growing body of evidence suggests that collagens are key components of peripheral nerves, where they not only provide a structural support but also affect cell behavior by triggering intracellular signals. In this review, we will summarize the main properties of collagen family, discuss the role of extensively studied collagen types (collagens IV, V, VI, and XV) in Schwann cell function and myelination, and provide a detailed overview of the recent advances with respect to these collagens in peripheral nerve function.

Cthrc1 is a negative regulator of myelination in Schwann cells

The analysis of the molecular mechanisms involved in the initial interaction between neurons and Schwann cells is a key issue in understanding the myelination process. We recently identified Cthrc1 (Collagen triple helix repeat containing 1) as a gene upregulated in Schwann cells upon interaction with the axon. Cthrc1 encodes a secreted protein previously shown to be involved in migration and proliferation in different cell types. We performed a functional analysis of Cthrc1 in Schwann cells by loss-of- and gain-of-function approaches using RNA interference knockdown in cell culture and a transgenic mouse line that overexpresses the gene. This work establishes that Cthrc1 enhances Schwann cell proliferation but prevents myelination. In particular, time-course analysis of myelin formation intransgenic animals reveals that overexpression of Cthrc1 in Schwann cells leads to a delay in myelin formation with cells maintaining a proliferative state. Our data, therefore, demonstrate that Cthrc1 plays a negative regulatory role, fine-tuning the onset of peripheral myelination.

Border patrol: insights into the unique role of perlecan/heparan sulfate proteoglycan 2 at cell and tissue borders

The extracellular matrix proteoglycan (ECM) perlecan, also known as heparan sulfate proteoglycan 2 or HSPG2, is one of the largest (>200 nm) and oldest (>550 M years) extracellular matrix molecules. In vertebrates, perlecan's five-domain structure contains numerous independently folding modules with sequence similarities to other ECM proteins, all connected like cars into one long, diverse complex train following a unique N-terminal domain I decorated with three long glycosaminoglycan chains, and an additional glycosaminoglycan attachment site in the C-terminal domain V. In lower invertebrates, perlecan is not typically a proteoglycan, possessing the majority of the core protein modules, but lacking domain I where the attachment sites for glycosaminoglycan chains are located. This suggests that uniting the heparan sulfate binding growth factor functions of domain I and the core protein functions of the rest of the molecule in domains II-V occurred later in evolution for a new functional purpose. In this review, we surveyed several decades of pertinent literature to ask a fundamental question: Why did nature design this protein uniquely as an extraordinarily long multifunctional proteoglycan with a single promoter regulating expression, rather than separating these functions into individual proteins that could be independently regulated? We arrived at the conclusion that the concentration of perlecan at functional borders separating tissues and tissue layers is an ancient key function of the core protein. The addition of the heparan sulfate chains in domain I likely occurred as an additional means of binding the core protein to other ECM proteins in territorial matrices and basement membranes, and as a means to reserve growth factors in an on-site depot to assist with rapid repair of those borders when compromised, such as would occur during wounding. We propose a function for perlecan that extends its role from that of an extracellular scaffold, as we previously suggested, to that of a critical agent for establishing and patrolling tissue borders in complex tissues in metazoans. We also propose that understanding these unique functions of the individual portions of the perlecan molecule can provide new insights and tools for engineering of complex multi-layered tissues including providing the necessary cues for establishing neotissue borders.

Establishment of immortalized Schwann cells derived from rat embryo dorsal root ganglia

Schwann cells (SCs) play an important role in the development, function and regeneration of peripheral nerves. They can enhance both peripheral and central nerve regeneration by providing a supportive environment for neurite outgrowth through the release of neurotrophic factors. However, use of primary SCs for in vitro models is limited because these cells are difficult to prepare and maintain in high yield and purity under common cell culture conditions. Human telomerase reverse transcriptase (hTERT) expression induces immortalization of various cell types without substantial alterations of their phenotypes. Therefore, in this study we transfected SCs with hTERT to establish a reliable cell source and observed the effect of hTERT on SCs. In order to accomplish this, SCs were isolated from rat embryo dorsal root ganglions, transfected with hTERT at early passage (passage 3). SCs passage 4, 8, 12 and 30 after transfection (hTERT-SCs) were used for immunocytochemistry, RT-PCR and western blotting. Results showed that all the early (passage 4) and late (passage 30) passage hTERT-SCs expressed hTERT mRNA and gained full telomerase activity. The transfection did not alter the mRNA expression of senescence-associated genes, such as p53 and p16. The expression of BDNF (brain-derived neurotrophic factor) was significantly decreased as cell passage increased, compared to the untransfected control. On the other hand, the expression of NGF (nerve growth factor ) was elevated at early passages (passages 4 and 8) and decreased at late passages (12 and 30). These data indicate that the use of specific immortalization techniques can establish SC lines that retain characteristics of typical primary SCs, and different mechanisms responsible for regulating NGF and BDNF expression. This is the first report regarding the immortalization of SCs derived from rat embryo dorsal root ganglions. These cells are useful in studies investigating the cellular mechanisms and regenerative processes of SCs.

IFN-beta pharmacogenomics in multiple sclerosis

Multiple sclerosis (MS) is a condition of the CNS marked by inflammation and neurodegeneration. Interferon (IFN)-beta was the first, and still is the main, immunomodulatory treatment for MS. Its clinical efficacy is limited, and a proportion of patients, ranging between 20-55%, do not respond to the therapy. Identification and subsequently, implementation in the clinic of biomarkers predictive for individual therapeutic response would facilitate improved patient care in addition to ensuring a more rational provision of this therapy. In this article, we summarize the main findings from studies addressing the pharmacogenomics of clinical response to IFN-beta in MS by either whole-genome association scans, candidate gene or transcriptomics studies. Whole-genome DNA association screens have revealed a high representation of brain-specific genes, and have hinted toward both extracellular ligand-gated ion channels and type I IFNs pathway genes as important categories of genetic IFN-beta response modifiers. One hit, glypican 5 (GPC5), was recently replicated in an independent study of IFN-beta responsiveness. Recent RNA transcriptomics studies have revealed the occurrence of a pre-existing type I IFN gene-expression signature, composed of genes that are predominantly induced by type I IFNs, as a potential contributing feature of poor response to therapy. Thus, while the outlines of a complex polygenic mechanism are gradually being uncovered, the main challenges for the near future will reside in the robust validation of identified response-modifying genes as well as in the decipherment of the mechanistic relationships between these genes and clinical response to IFN-beta.

Novel method to obtain highly enriched cultures of adult rat Schwann cells

Schwann cells (SCs) can be used to repair both the peripheral and central nervous systems. Therefore, establishment of a procedure to obtain activated, highly proliferative SCs, in an appropriate time for clinical applications, is a prerequisite. Purification is complicated by contamination with fibroblasts which often become the predominant cell type in an in vitro SC culture. This study describes a novel and efficient method to enrich SCs by utilizing the differential detachment properties of the two cell types. In culture, cells were treated with two different media and the chelator, EGTA, which detached SCs faster than fibroblasts and allowed for easy isolation of SCs. Within seven days, high yields of SCs with a purity of greater than 99% were achieved. This was confirmed by immunostaining characterization and flow-cytometric analyses using an antibody against the p75 low affinity nerve growth factor receptor (p75LNGFR). The entire procedure was completed in approximately 21 days. This method has the advantage of being technically easier, faster, and more efficient than other previously described methods. An SC culture that was about 99% homogenous was achieved.

An improved method for isolating Schwann cells from postnatal rat sciatic nerves

The major difficulty in Schwann cell (SC) purification is contamination by fibroblasts, which usually become the predominant cell type during SC enrichment in vitro. Current reported measures are mainly limited by either high cost or complicated procedures with low cell yields or purity. Our objectives have been to develop an efficient, easily applicable, rapid method to obtain highly purified SC from the sciatic nerve of newborn rats. The method involves two rounds of purification to eliminate fibroblasts with the novel combined use of cytosine-B-arabinoside hydrochloride (Ara-C) action and differential cell detachment. Cultured cells were first treated with Ara-C for 24 h. The medium was replaced with the growth medium containing 20 ng/ml human heregulin1-beta1 extracellular domain (HRG1-beta1 ECD). After another 48 h in culture, the cells were treated with 0.05% trypsin, following which SCs, but not fibroblasts, were easily detached from the dishes. The advantage of this method is that the two steps can eliminate the fibroblasts complementarily. Ara-C eliminates most of the fibroblasts growing among SCs, whereas the differential cell detachment technique removes the remainder growing under or interacting with the SC layer. A purity of more than 99% SCs has been obtained, as confirmed by cell morphology and immunostaining. The purified SCs have a spindle-shaped, bipolar, and sometimes tripolar morphology, align in fascicles, and express S-100. The whole procedure takes about 10 days from primary culture to the purified SCs growing to confluence (only half the time reported previously). This protocol provides an alternative method for investigating peripheral nerve regeneration and potentially could be used to produce enough SCs to construct artificial nerve scaffolds in vitro.

Regulation of Schwann cell function by the extracellular matrix

Laminins and collagens are extracellular matrix proteins that play essential roles in peripheral nervous system development. Laminin signals regulate Schwann cell proliferation and survival as well as actin cytoskeleton dynamics, which are essential steps for radial sorting and myelination of peripheral axons by Schwann cells. Collagen and their receptors promote Schwann cell adhesion, spreading, and myelination as well as neurite outgrowth. In this article, we will review the recent advances in the studies of laminin and collagen function in Schwann cell development.

Detection of V, III and I type collagens of dermal tissues in skin lesions of patients with systemic sclerosis and its implication

This study investigated the contents and distribution of collagen V (Col V) in skin lesions of the patients with systemic sclerosis (SSc) and its roles in the pathogenesis. The contents and distribution for alpha1 chain of collagen type I, III and V [alpha1 (I), alpha1 (III) and alpha1 (V)] in skin lesions of 36 patients with SSc (9 cases of mild fibrosis, 14 moderate, and 13 severe) were detected by using immunohistochemical SP method. Six cases of normal skin tissues served as controls. The results showed that there was diffuse distribution for three kinds of collagens in dermis. The deep staining alpha1 (I) and alpha1 (III) masses or bands were seen in reticular layer, while alpha1 (V) was distributed more homogeneously. From control to weak, moderate and severe fibrosis stages, alpha1 (I), alpha1 (III) and alpha1 (V) showed a gradually increased trend in skin lesions (P<0.05). alpha1 (V) was obviously elevated in skin lesions at early stage and persisted in whole fibrotic process and risen in greater contents, while alpha1 (I) and alpha1 (III) were to go higher late and were apparently elevated at moderate and late stages. Compared with alpha1 (I), alpha1 (V) took leading increase at early stage in skin lesions (P<0.01), and had more elevated contents than alpha1 (III) at moderate and late stages. The fibrotic changes in dermal reticular layer occurred earlier than those in papillary layer, and the abnormalities of alpha1 (V)/alpha1 (I) ratio appeared before alpha1 (III)/alpha1 (I) ratio. It was concluded that a lot of alpha1 (V) began to deposit in greater contents prior to alpha1 (I) and alpha1 (III) at early stage in SSc and persisted in whole fibrotic process. The changes of alpha1 (V) contents in reticular layer occurred earlier than those in papillary layer, and it suggested that the fibrosis in reticular layer appeared earlier.

Secreted gliomedin is a perinodal matrix component of peripheral nerves

The interaction between gliomedin and the axonodal cell adhesion molecules (CAMs) neurofascin and NrCAM induces the clustering of Na⁺ channels at the nodes of Ranvier. We define new interactions of gliomedin that are essential for its clustering activity. We show that gliomedin exists as both transmembrane and secreted forms that are generated by proteolytic cleavage of the protein, and that only the latter is detected at the nodes of Ranvier. The secreted extracellular domain of gliomedin binds to Schwann cells and is incorporated into the extracellular matrix (ECM) in a heparin-dependent manner, suggesting the involvement of heparan sulfate proteoglycans (HSPGs). Furthermore, we show that the N-terminal region of gliomedin serves as an oligomerization domain that mediates self-association of the molecule, which is required for its binding to neurofascin and NrCAM. Our results indicate that the deposition of gliomedin multimers at the nodal gap by binding to HSPGs facilitates the clustering of the axonodal CAMs and Na⁺ channels.

Aging Schwann cells in vitro

Schwann cells (SCs) can support the regeneration of lesioned fiber tracts of the peripheral and central nervous system and have been transplanted alone or in combination with synthetic nerve guides. For neuronal tissue engineering purposes, the cells must be isolated from small biopsies and expanded in vitro. In this study we analyze the impact of cell expansion on 9 different cell parameters, comparing short- and long-term cultured rat SCs, which we refer to as 'young' and 'old' or 'aged' cells, respectively. In comparison to young SCs, old SCs doubled the axonal outgrowth from dorsal root ganglion explants and displayed only one-third as much adhesion to the gray and white matter of spinal cord cryosections. In a 3-dimensional extracellular matrix the two cell populations showed very different cellular responses with regard to cell morphology and cell-cell adhesion. Cell proliferation of old SCs was independent of serum components and was not hampered by contact inhibition. In addition, population doubling times were reduced by a factor of almost three compared to those of young SCs. Despite considerable karyotype changes, with an average of 68.7 chromosomes versus 42 in native rat cells, old SCs did not show any increase in telomerase activity and loss of anchorage dependence--characteristics that are typical of tumor cells. The data also provide biological insights into which cell characteristics (proliferation and adhesion, for example) are functionally clustered and either change or remain constant with aging in vitro. Though the data indicate a lack of tumorigenic transformation coupled with increased neurite outgrowth-promoting activity after extensive SC expansion in vitro, thus suggesting better regeneration qualities, we strongly recommend that in vitro aged rat SCs (>11 passages) should not be employed for tissue engineering.

Neuregulin isoforms in dorsal root ganglion neurons: effects of the cytoplasmic domain on localization and membrane shedding of Nrg-1 type I

Embryonic sensory neurons express membrane-anchored growth factors that stimulate proliferation and differentiation of Schwann cells. The most important of these are members of the neuregulin-1 (Nrg-1) family that activate the erbB2/erbB3 receptor kinase on Schwann cells. Nrg-1 growth factors display a complex pattern of alternative mRNA splicing. We investigated the expression of the Nrg-1 type I in rat embryo dorsal root ganglion (DRG) neurons. Nrg-1 type I mRNA was abundantly expressed in DRG neurons; molecular cloning identified three distinct isoforms. The most prominent structural difference produced by alternative splicing was truncation of the C-terminal cytoplasmic domain. In sensory neurons and other cells, Nrg-1 type I proteins with the full-length 374-amino-acid cytoplasmic domain were expressed on the cell surface. In contrast, an isoform with a partially truncated cytoplasmic domain was retained in an intracellular compartment. Deletion studies demonstrated the presence of a cryptic intracellular retention signal that was exposed in the truncated cytoplasmic domain. Cell surface Nrg-1 type I molecules were subject to protease-dependent release of the biologically active ectodomain. As a consequence of their intracellular localization, the Nrg-1 type I isoform with a truncated cytoplasmic domain was not subject to membrane shedding. Nrg-1 type I ectodomain release was accelerated by factors present in Schwann cell-conditioned medium. In cells with active Nrg-1 type I ectodomain, shedding products corresponding to the cytoplasmic domain were not detected, because of rapid gamma-secretase- and proteasome-dependent degradation. These results demonstrate that sensory neurons express alternatively spliced neuregulin polypeptides with distinct subcellular localizations and processing.

Patients with Ehlers Danlos syndrome and CRPS: a possible association?

Rare patients are left with chronic pain, vasodysregulation, and other symptoms that define complex regional pain syndrome (CRPS), after limb traumas. The predisposing factors are unknown. Genetic factors undoubtedly contribute, but have not yet been identified. We report four CRPS patients also diagnosed with the classical or hypermobility forms of Ehlers Danlos syndrome (EDS), inherited disorders of connective tissue. These patients had been diagnosed using standard diagnostic criteria for CRPS and for EDS. All had sustained joint injury; in three this had been surgically treated. The association of these two diagnoses leads us to hypothesize that EDS might contribute to the development of CRPS in one or more of the following ways: via stretch injury to nerves traversing hypermobile joints, increased fragility of nerve connective tissue, or nerve trauma from more frequent surgery. We review the clinical presentation of the different Ehlers Danlos syndromes and provide clinical criteria that can be used to screen CRPS patients for EDS for clinical or research purposes.

Glypican-1 and alpha4(V) collagen are required for Schwann cell myelination

Schwann cell myelination requires interactions with the extracellular matrix (ECM) mediated by cell surface receptors. Previously, we identified a type V collagen family member, alpha4(V) collagen, which is expressed by Schwann cells during peripheral nerve differentiation. This collagen binds with high affinity to heparan sulfate through a unique binding motif in the noncollagenous N-terminal domain (NTD). The principal alpha4(V) collagen-binding protein on the Schwann cell surface is the heparan sulfate proteoglycan glypican-1. We investigated the role of alpha4(V) collagen and glypican-1 in Schwann cell terminal differentiation in cultures of Schwann cells and dorsal root ganglion neurons. Small interfering RNA-mediated suppression of glypican-1 expression decreased binding of alpha4(V)-NTD to Schwann cells, adhesion and spreading of Schwann cells on alpha4(V)-NTD, and incorporation of alpha4(V) collagen into Schwann cell ECM. In cocultures, alpha4(V) collagen coassembles with laminin on the surface of polarized Schwann cells to form tube-like ECM structures that are sites of myelination. Suppression of glypican-1 or alpha4(V) collagen expression significantly inhibited myelination. These results demonstrate an important role for these proteins in peripheral nerve terminal differentiation.

The structures of the thrombospondin-1 N-terminal domain and its complex with a synthetic pentameric heparin

The N-terminal domain of thrombospondin-1 (TSPN-1) mediates the protein's interaction with (1) glycosaminoglycans, calreticulin, and integrins during cellular adhesion, (2) low-density lipoprotein receptor-related protein during uptake and clearance, and (3) fibrinogen during platelet aggregation. The crystal structure of TSPN-1 to 1.8 A resolution is a beta sandwich with 13 antiparallel beta strands and 1 irregular strand-like segment. Unique structural features of the N- and C-terminal regions, and the disulfide bond location, distinguish TSPN-1 from the laminin G domain and other concanavalin A-like lectins/glucanases superfamily members. The crystal structure of the complex of TSPN-1 with heparin indicates that residues R29, R42, and R77 in an extensive positively charged patch at the bottom of the domain specifically associate with the sulfate groups of heparin. The TSPN-1 structure and identified adjacent linker region provide a structural framework for the analysis of the TSPN domain of various molecules, including TSPs, NELLs, many collagens, TSPEAR, and kielin.

Collagen XXVIII, a novel von Willebrand factor A domain-containing protein with many imperfections in the collagenous domain

Here we describe a novel collagen belonging to the class of von Willebrand factor A (VWA) domain-containing proteins. This novel protein was identified by screening the EST data base and was subsequently recombinantly expressed and characterized as an authentic tissue component. The COL28A1 gene on human chromosome 7p21.3 and on mouse chromosome 6A1 encodes a novel protein that structurally resembles the beaded filament-forming collagens. The collagenous domain contains several very short interruptions arranged in a repeat pattern. As shown for other novel minor collagens, the expression of collagen XXVIII protein in mouse is very restricted. In addition to small amounts in skin and calvaria, the major signals were in dorsal root ganglia and peripheral nerves. By immunoelectron microscopy, collagen XXVIII was detected in the sciatic nerve, at the basement membrane of certain Schwann cells surrounding the nerve fibers. Even though the protein is present in the adult sciatic nerve, collagen XXVIII mRNA was only detected in sciatic nerve of newborn mice, indicating that the protein persists for an extended period after synthesis.

Domains and Maturation Processes That Regulate the Activity of ADAMTS-2, a Metalloproteinase Cleaving the Aminopropeptide of Fibrillar Procollagens Types I–III and V

Processing of fibrillar collagens is required to generate collagen monomers able to self-assemble into elongated and cylindrical collagen fibrils. ADAMTS-2 belongs to the "A disintegrin and metalloproteinase with thrombospondin type 1 motifs" (ADAMTS) family. It is responsible for most of the processing of the aminopropeptide of type I procollagen in the skin, and it also cleaves type II and type III procollagens. ADAMTS are complex secreted enzymes that are implicated in various physiological and pathological processes. Despite accumulating evidence indicating that their activity is regulated by ancillary domains, additional information is required for a better understanding of the specific function of each domain. We have generated 17 different recombinant forms of bovine ADAMTS-2 and characterized their processing, activity, and cleavage specificity. The results indicated the following: (i) activation of the ADAMTS-2 zymogen involves several cleavages, by proprotein convertases and C-terminal processing, and generates at least seven distinct processed forms; (ii) the C-terminal domain negatively regulates enzyme activity, whereas two thrombospondin type 1 repeats are enhancer regulators; (iii) the 104-kDa form displays the highest aminoprocollagen peptidase activity on procollagen type I; (iv) ADAMTS-2 processes the aminopropeptide of alpha1 type V procollagen homotrimer at the end of the variable domain; and (v) the cleaved sequence (PA) is different from the previously described sites ((P/A)Q) for ADAMTS-2, redefining its cleavage specificity. This finding and the existence of multiple processed forms of ADAMTS-2 strongly suggest that ADAMTS-2 may be involved in function(s) other than processing of fibrillar procollagen types I-III.

Pro-α3(V) collagen chain is expressed in bone and its basic N-terminal peptide adheres to osteosarcoma cells

The third alpha-chain of type V collagen, alpha3(V) chain, was initially identified in the placenta more than 20 years ago, but was poorly characterized with regard to its expression and function. We generated a specific monoclonal antibody against the N-terminal domain of the pro-alpha3(V) chain and examined gene expression using immunohistochemical methods combined with in situ hybridization. The pro-alpha3(V) chain was seen in funis and amnion, but not chorionic villi and deciduas of mouse placenta. In mouse embryo, the transcripts of the pro-alpha3(V) gene were seen in tissues that were related to bone formation as well as developing muscle and nascent ligament previously reported. However, immunohistochemistry showed that pro-alpha3(V) protein accumulated rather in the developing bone of mouse embryo. On the other hand, the N-terminal globular domain of the pro-alpha3(V) chain has a unique structure that contains a highly basic segment of 23 amino acids. The peptide derived from the basic segment showed a specific adhesive feature to osteosarcoma cells but not to chondrosarcoma cells. The four heparin binding sites in the basic segment equally contribute toward adhesion to the osteosarcoma cells. Our data suggested that N-terminal globular domain of the pro-alpha3(V) chain influence bone formation of osteoblasts through proteoglycan on the cell surface during development or regeneration.