Plasminogen activation triggers transthyretin amyloidogenesis in vitro.

Systemic amyloidosis is a usually fatal disease caused by extracellular accumulation of abnormal protein fibers, amyloid fibrils, derived by misfolding and aggregation of soluble globular plasma protein precursors. Both WT and genetic variants of the normal plasma protein transthyretin (TTR) form amyloid, but neither the misfolding leading to fibrillogenesis nor the anatomical localization of TTR amyloid deposition are understood. We have previously shown that, under physiological conditions, trypsin cleaves human TTR in a mechano-enzymatic mechanism that generates abundant amyloid fibrils in vitro In sharp contrast, the widely used in vitro model of denaturation and aggregation of TTR by prolonged exposure to pH 4.0 yields almost no clearly defined amyloid fibrils. However, the exclusive duodenal location of trypsin means that this enzyme cannot contribute to systemic extracellular TTR amyloid deposition in vivo Here, we therefore conducted a bioinformatics search for systemically active tryptic proteases with appropriate tissue distribution, which unexpectedly identified plasmin as the leading candidate. We confirmed that plasmin, just as trypsin, selectively cleaves human TTR between residues 48 and 49 under physiological conditions in vitro Truncated and full-length protomers are then released from the native homotetramer and rapidly aggregate into abundant fibrils indistinguishable from ex vivo TTR amyloid. Our findings suggest that physiological fibrinolysis is likely to play a critical role in TTR amyloid formation in vivo Identification of this surprising intersection between two hitherto unrelated pathways opens new avenues for elucidating the mechanisms of TTR amyloidosis, for seeking susceptibility risk factors, and for therapeutic innovation.

Co-fibrillogenesis of Wild-type and D76N ß2-Microglobulin: THE CRUCIAL ROLE OF FIBRILLAR SEEDS.

The amyloidogenic variant of ß2-microglobulin, D76N, can readily convert into genuine fibrils under physiological conditions and primes in vitro the fibrillogenesis of the wild-type ß2-microglobulin. By Fourier transformed infrared spectroscopy, we have demonstrated that the amyloid transformation of wild-type ß2-microglobulin can be induced by the variant only after its complete fibrillar conversion. Our current findings are consistent with preliminary data in which we have shown a seeding effect of fibrils formed from D76N or the natural truncated form of ß2-microglobulin lacking the first six N-terminal residues. Interestingly, the hybrid wild-type/variant fibrillar material acquired a thermodynamic stability similar to that of homogenous D76N ß2-microglobulin fibrils and significantly higher than the wild-type homogeneous fibrils prepared at neutral pH in the presence of 20% trifluoroethanol. These results suggest that the surface of D76N ß2-microglobulin fibrils can favor the transition of the wild-type protein into an amyloid conformation leading to a rapid integration into fibrils. The chaperone crystallin, which is a mild modulator of the lag phase of the variant fibrillogenesis, potently inhibits fibril elongation of the wild-type even once it is absorbed on D76N ß2-microglobulin fibrils.

Severe Peripheral Joint Laxity is a Distinctive Clinical Feature of Spondylodysplastic-Ehlers-Danlos Syndrome (EDS)-B4GALT7 and Spondylodysplastic-EDS-B3GALT6.

Variations in genes encoding for the enzymes responsible for synthesizing the linker region of proteoglycans may result in recessive conditions known as "linkeropathies". The two phenotypes related to mutations in genes B4GALT7 and B3GALT6 (encoding for galactosyltransferase I and II respectively) are similar, characterized by short stature, hypotonia, joint hypermobility, skeletal features and a suggestive face with prominent forehead, thin soft tissue and prominent eyes. The most outstanding feature of these disorders is the combination of severe connective tissue involvement, often manifesting in newborns and infants, and skeletal dysplasia that becomes apparent during childhood. Here, we intend to more accurately define some of the clinical features of B4GALT7 and B3GALT6-related conditions and underline the extreme hypermobility of distal joints and the soft, doughy skin on the hands and feet as features that may be useful as the first clues for a correct diagnosis.

Cutaneous metaplastic synovial cyst in Ehlers-Danlos syndrome: report of a second case.

A cutaneous metaplastic synovial cyst is a rare entity that is probably caused by trauma or surgery. We report the second case of cutaneous metaplastic synovial cyst in a child with Ehlers-Danlos syndrome. His father is also affected with Ehlers-Danlos syndrome, and his diagnosis is substantiated by the demonstration of reduced synthesis of collagen type V.

Wound repair capability in EDS fibroblasts can be retrieved by exogenous type V collagen.

Impaired wound healing is a typical clinical hallmark of Ehlers-Danlos Syndrome (EDS). Mutated fibroblasts from EDS patients, which deposit an abnormal extracellular matrix, showed defective migration resulting in a marked delay in wound repair. The migratory capability remarkably improved in the presence of exogenous type V collagen.

Subependymal periventricular heterotopias in a patient with ehlers-danlos syndrome: a new case.

Ehlers-Danlos syndrome is a complex hereditary connective tissue disorder that is characterized by abnormalities of the skin and joints and visceral and neurological manifestations. At present, at least 11 forms are recognized on the basis of their clinical characteristics, methods of transmission, and biochemical defect. The neurologic manifestations include cerebrovascular disease, peripheral neuropathy, plexopathy, periventricular subependymal heterotopias, and epilepsy. Previously, 2 females were reported to be affected with subependimal periventricular heterotopias and Ehlers-Danlos syndrome type 1. The authors report a new case of a 12-year-old girl with similar clinical and neuroradiological features.

A specific nanobody prevents amyloidogenesis of D76N ß2-microglobulin in vitro and modifies its tissue distribution in vivo.

Systemic amyloidosis is caused by misfolding and aggregation of globular proteins in vivo for which effective treatments are urgently needed. Inhibition of protein self-aggregation represents an attractive therapeutic strategy. Studies on the amyloidogenic variant of ß2-microglobulin, D76N, causing hereditary systemic amyloidosis, have become particularly relevant since fibrils are formed in vitro in physiologically relevant conditions. Here we compare the potency of two previously described inhibitors of wild type ß2-microglobulin fibrillogenesis, doxycycline and single domain antibodies (nanobodies). The ß2-microglobulin -binding nanobody, Nb24, more potently inhibits D76N ß2-microglobulin fibrillogenesis than doxycycline with complete abrogation of fibril formation. In ß2-microglobulin knock out mice, the D76N ß2-microglobulin/ Nb24 pre-formed complex, is cleared from the circulation at the same rate as the uncomplexed protein; however, the analysis of tissue distribution reveals that the interaction with the antibody reduces the concentration of the variant protein in the heart but does not modify the tissue distribution of wild type ß2-microglobulin. These findings strongly support the potential therapeutic use of this antibody in the treatment of systemic amyloidosis.

5-methyl-pyrrolidinone chitosan films as carriers for buccal administration of proteins.

The purpose of this research was to investigate 5-methyl-pyrrolidinone chitosan (MPC) films as carriers for buccal delivery of protein drugs. Placebo and protein-loaded MPC films were prepared by casting and were then cross-linked with tripolyphosphate at different pH conditions. Myoglobin (MHb) was chosen as the model protein because its molecular weight is under the permeability limit of the buccal mucosa. The observed characteristics like bioadhesiveness, swelling behavior, and in vitro release of MHb from loaded films furnish information on the functional behavior of these films. The results obtained show that the modulation of MHb release was achieved only through chitosan cross-linking; the best results in release rate control were obtained by cross-linking performed at pH 6.5. Good bioadhesion properties were maintained even with high cross-linking degrees; the swelling index of MHb-loaded films at different cross-linking degrees evaluated at pH 7.4 and pH 6.4 were comparable to those of placebo films. By setting suitable tripolyphosphate cross-linking conditions for MPC films, one can control protein release without affecting bioadhesion.

Cardiac valve disease: an unreported feature in Ehlers Danlos syndrome arthrocalasia type?

Ehlers Danlos syndrome (EDS) athrocalasia type (type VII), is characterized by joint hypermobility, skin hyperextensibility and tissue fragility. No heart involvement has been reported. Two forms have been described: type VII A and VII B. The abnormally processed collagen α2(I) and the skipping of the exon 6 in COL1A2 gene are typically detected in EDS type VII B. We describe a seven-year old female, with a phenotype consistent with EDS type VII B and a diagnosis further confirmed by biochemical and molecular analyses. Cardiac ultrasound showed normal data in the first year of life. When she was 5 years old, the patient developed mitral valve regurgitation, and aortic and tricuspidal insufficiency at 7 years of age. To our knowledge, this is the first report of cardiac valvular involvement in EDS VII B. This feature probably has been underreported for the limited follow-up of the patients. Echocardiography might be warranted in the clinical assessment of EDS VII patients.

Lack of expression of SERPINF1, the gene coding for pigment epithelium-derived factor, causes progressively deforming osteogenesis imperfecta with normal type I collagen.

Osteogenesis imperfecta (OI) is a clinically heterogeneous heritable connective tissue disorder, characterized by low bone mass and reduced strength, which result in susceptibility to fracture and bone deformities. In most cases it is caused by dominant mutations in type I collagen genes, COL1A1 and COL1A2. Recessive forms, which collectively account for approximately 5% of cases of osteogenesis imperfecta detected in North America and Europe, are caused instead by mutations in various genes coding for proteins involved in collagen posttranslational modifications, folding, and secretion. A novel disease locus, SERPINF1, coding for pigment epithelium-derived factor (PEDF), has been found recently. In SERPINF1 mutants described so far, synthesis, posttranslational modification, and secretion of type I collagen were reported to be normal. Here we describe three siblings born to consanguineous parents, who show an initially mild and then progressively worsening form of OI with severe deformities of the long bones. They are homozygous for a frameshift mutation in exon 4 of the SERPINF1 gene, which leads to lack of the transcription/translation product, likely a key factor in bone deposition and remodeling. Synthesis and secretion of type I collagen are normal. Clinical, radiographic, histological, and histomorphometric data from the proband are reminiscent of the distinctive features of type VI OI.

Identification of the amniotic fluid insulin-like growth factor binding protein-1 phosphorylation sites and propensity to proteolysis of the isoforms.

Insulin-like growth factor binding protein-1 (IGFBP-1) is the major secreted protein of human decidual cells during gestation and, as a modulator of insulin-like growth factors or by independent mechanisms, regulates embryonic implantation and growth. The protein is phosphorylated and this post-translational modification is regulated in pregnancy and represents an important determinant of its biological activity. We have isolated, from human normal amniotic fluid collected in the weeks 16-18, the intact nonphosphorylated IGFBP-1 and five electrophoretically distinct phosphoisoforms and have determined their in vivo phosphorylation state. The unmodified protein was the most abundant component and mono-, bi-, tri- and tetraphosphorylated forms were present in decreasing amounts. The phosphorylation sites of IGFBP-1 were identified by liquid chromatography-tandem mass spectrometry analysis of the peptides generated with trypsin, chymotrypsin and Staphylococcus aureus V8 protease. Five serines were found to be phosphorylated and, of these, four are localized in the central, weakly conserved, region, at positions 95, 98, 101 and 119, whereas one, Ser169, is in the C-terminal domain. The post-translational modification predominantly involves the hydrophilic stretch of amino acids representing a potential PEST sequence (proline, glutamic acid, serine, threonine) and our results show that the phosphorylation state influences the propensity of IGFBP-1 to proteolysis.

Rescue of migratory defects of Ehlers-Danlos syndrome fibroblasts in vitro by type V collagen but not insulin-like binding protein-1.

Mutations in the genes encoding for type V collagen have been found in the classical type of Ehlers-Danlos syndrome (EDS); the most common mutations lead to a non-functional COL5A1 allele. We characterized three skin fibroblast strains derived from patients affected by classical EDS caused by COL5A1 haploinsufficiency. As a typical clinical hallmark of EDS is the impaired wound healing, we analyzed the repair capability of fibroblasts in a monolayer wounding assay. The mutant fibroblast strains were unable to move into the scraped area showing then a marked delay in wound repair. In all the EDS strains, type V collagen was absent in the extracellular space, also leading to the lack of fibronectin fibrillar network and impairing the expression of alpha(2)beta(1) and alpha(5)beta(1) integrins. The abnormal integrin pattern inhibited the positive effect of insulin-like growth factor-binding protein-1 on cell migration, whereas the migratory capability remarkably improved in the presence of exogenous type V collagen.

Structure and properties of the C-terminal domain of insulin-like growth factor-binding protein-1 isolated from human amniotic fluid.

Insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) regulates the activity of the insulin-like growth factors in early pregnancy and is, thus, thought to play a key role at the fetal-maternal interface. The C-terminal domain of IGFBP-1 and three isoforms of the intact protein were isolated from human amniotic fluid, and sequencing of the four N-terminal polypeptide chains showed them to be highly pure. The addition of both intact IGFBP-1 and its C-terminal fragment to cultured fibroblasts has a similar stimulating effect on cell migration, and therefore, the domain has a biological activity on its own. The three-dimensional structure of the C-terminal domain was determined by x-ray crystallography to 1.8 Angstroms resolution. The fragment folds as a thyroglobulin type I domain and was found to bind the Fe(2+) ion in the crystals through the only histidine residue present in the polypeptide chain. Iron (II) decreases the binding of intact IGFBP-1 and the C-terminal domain to IGF-II, suggesting that the metal binding site is close to or part of the surface of interaction of the two molecules.