Latent-transforming Growth Factor Beta-binding Protein 2 Research Articles

LTBP2 Knockdown Ameliorates Cardiac Fibrosis and Apoptosis via Attenuating NF‐κB Signaling Pathway and Oxidative Stress in Mice with Cardiac Hypertrophy

AbstractAt present, there is no therapeutic approach available to reverse the progression of pathological fibrosis and ventricle chamber stiffening. This study is designed to explore the effects of latent transforming growth factor‐beta‐binding protein 2 (LTBP2) on cardiac fibrosis in hypertrophic cardiomyopathy and the underlying mechanisms. The key differential gene LTBP2 is identified by mRNA sequencing. Ang II‐induced cells and mice are treated with LTBP2 si‐RNA or knockdown adenovirus, respectively, and the indicators of cardiac function, oxidative stress, cardiac fibrosis, apoptosis, and remodeling are examined. The underlying mechanism is elucidated in vitro by oxidative stress and an agonist of nuclear factor‐kappa B (NF‐κB). LTBP2 is upregulated in the cardiac tissue of mice with Ang II‐mediated HF. The knockdown of LTBP2 enhanced cardiac function, attenuated cardiac fibrosis, apoptosis, hypertrophy, and oxidative stress injury, and suppressed NF‐κB expression. These results are validated in vitro. The effects of LTBP2 gene silencing are reversed by either NF‐κB or oxidative stress agonists in vitro. Taken together, these findings suggest that LTBP2 knockdown alleviates HF by inhibiting cardiac fibrosis, apoptosis, and hypertrophy via attenuating NF‐κB signaling pathway and oxidative stress. Thus, targeting LTBP2 may be a novel approach to the treatment of HF.

Autosomal Dominant Weill-Marchesani-Like Syndrome in a Chinese Family due to Novel Haplotypic Mutations in LTBP2.

Weill-Marchesani syndrome (WMS) is a hereditary connective tissue disorder with substantial heterogeneity in clinical features and genetic etiology, so it is essential to define the full mutation spectrum for earlier diagnosis. In this study, we report Weill-Marchesani-like syndrome (WMS-like) change to autosomal dominance inheritance caused by novel haplotypic mutations in latent transforming growth factor beta-binding protein 2 (LTBP2). Twenty-five members from a 4-generation Chinese family were recruited from Guangzhou, of whom nine were diagnosed with WMS-like disease, nine were healthy, and seven were of "uncertain" clinical status because of their young age. All members received detailed physical and ocular examinations. Whole-exome sequencing, Sanger sequencing, and real-time PCR were used to identify and verify the causative mutations in family members. Genetic sequencing revealed novel haplotypic mutations on the same LTBP2 chromosome associated with WMS-like, c. 2657C>A/p.T886K in exon 16 and deletion of exons 25-36. Real-time PCR and Sanger sequencing verified both mutations in patients with clinically diagnosed WMS-like, and in one "uncertain" child. In these patients, the haplotypic mutations led to ectopia lentis, short stature, and obesity. Our study revealed that WMS-like may be associated with haplotypic LTBP2 mutations with autosomal dominant inheritance.

Exploring the Genetic Landscape of Childhood Glaucoma.

Childhood glaucoma, a significant cause of global blindness, represents a heterogeneous group of disorders categorized into primary or secondary forms. Primary childhood glaucoma stands as the most prevalent subtype, comprising primary congenital glaucoma (PCG) and juvenile open-angle glaucoma (JOAG). Presently, multiple genes are implicated in inherited forms of primary childhood glaucoma. This comprehensive review delves into genetic investigations into primary childhood glaucoma, with a focus on identifying causative genes, understanding their inheritance patterns, exploring essential biological pathways in disease pathogenesis, and utilizing animal models to study these mechanisms. Specifically, attention is directed towards genes such as CYP1B1 (cytochrome P450 family 1 subfamily B member 1), LTBP2 (latent transforming growth factor beta binding protein 2), TEK (TEK receptor tyrosine kinase), ANGPT1 (angiopoietin 1), and FOXC1 (forkhead box C1), all associated with PCG; and MYOC (myocilin), associated with JOAG. Through exploring these genetic factors, this review aims to deepen our understanding of the intricate pathogenesis of primary childhood glaucoma, thereby facilitating the development of enhanced diagnostic and therapeutic strategies.

PAUL device implantation in paediatric glaucoma patients with LTBP2 mutation: Case reports

Purpose: Latent‐transforming growth factor beta‐binding protein 2 (LTBP2) is a fibrillin‐related extracellular matrix protein. The protein is expressed in the ciliary body, and mutations in its gene lead to primary paediatric glaucoma due to anterior segment dysgenesis. These mutations in the Greek area appear almost exclusively in Roma families. In this work, we present the surgical treatment of two patients with PAUL® device implantation, and their preoperative and postoperative course.Methods: Case Reports.Results: Case 1: A 2‐month‐old female patient, the fifth child of a Roma family with an older sister with paediatric glaucoma, presented to the Ophthalmology clinic of our hospital with microspherophakia and megalocornea, a phenotype compatible with a mutation of the LTBP2 gene. She underwent a phakectomy for lens dislocation in both eyes. At the age of 2.5 years, she was diagnosed with hypertony and started topical treatment. After two years of treatment escalation and unsuccessful management of intraocular pressure, at the age of 4.5 years it was decided to implant a PAUL® glaucoma implant in her left eye. Case 2: An 8‐month‐old male patient, child of a Roma family, similarly presented with microspherophakia and megalocornea as well as hypertony. In addition to topical treatment, he underwent peripheral iridectomies and phakectomies in both eyes. After years of treatment escalation and unsuccessful management of intraocular pressure, at the age of 6.5 years it was decided to implant a PAUL® glaucoma implant in his left eye. We describe the surgical procedures as well as their postoperative course.Conclusions: Regular monitoring of intraocular pressure is recommended in children with megalocornea, microspherophakia and/or ectopia lentis. Genetic testing of the LTBP2 gene is recommended in these patients. It is important to raise awareness in the ophthalmological community regarding the recognition of this phenotype in children of Roma families. The PAUL® device is one of the options for treating drug‐resistant paediatric glaucoma.

Abstract 12653: Plasma LTBP-2 is Associated With Myocardial LTBP-2 and Poor Prognosis in Dilated Cardiomyopathy

Introduction: Cardiac extracellular matrix proteins provide structural support to the heart function and are associated with fibrosis in dilated cardiomyopathy (DCM). Latent transforming growth factor beta-binding protein 2 (LTBP-2) is a type of extracellular matrix protein, but the significance of LTBP-2 in patients with dilated cardiomyopathy is still unclear. Objective: To elucidate the significance of LTBP-2 in dilated cardiomyopathy. Methods: Plasma LTBP-2 levels were measured by Enzyme-linked immunosorbent assay in 131 DCM patients who underwent endomyocardial biopsy and 44 controls who had no history of cardiac diseases. Immunohistochemistry for LTBP-2, LTBP-1 (another LTBP family member), and Elastica-Masson staining were performed in endomyocardial biopsy specimens. DCM patients were followed up for cardiac death or ventricular assist device (VAD) implantation. Results: DCM patients had elevated plasma LTBP-2 levels compared to controls (104 vs. 57 ng/mL, P < 0.001). Plasma LTBP-2 levels were positively correlated with LTBP-2-positive fraction in the myocardium from the biopsy specimen (R = 0.311, P < 0.001). Myocardial LTBP-2-positive fraction was positively correlated with myocardial LTBP-1-positive fraction (R = 0.444, P = 0.014) and fibrosis fraction estimated by Elastica-Masson staining (R = 0.387, P < 0.001). In the Kaplan-Meier analysis, the high plasma LTBP-2 concentration group and the high myocardial LTBP-2-positive fraction group had more cardiac deaths or VAD implantations than low groups (P = 0.008 and P < 0.001, respectively). Multivariable Cox proportional hazard analysis showed that plasma LTBP-2 and myocardial LTBP-2-positive fraction were independently associated with cardiac death or VAD implantation. Conclusion: Plasma LTBP-2 reflects myocardial LTBP-2 and can be a biomarker to predict adverse outcomes in DCM patients.

Genome-wide association study using a single-step approach for teat number in Duroc, Landrace and Yorkshire pigs in Korea.

We investigated the genetic basis of teat number in sows, which is an important factor in their reproductive performance. We collected genotyping data from 20 353 pigs of three breeds (Duroc, Landrace and Yorkshire) using the Porcine SNP60K Bead Chip, and analyzed phenotypic data from 240 603 pigs. The heritability values of total teat number were 0.33 ± 0.02, 0.51 ± 0.01 and 0.50 ± 0.01 in Duroc, Landrace and Yorkshire pigs, respectively. A genome-wide association study was used to identify significant chromosomal regions associated with teat number in SSC7 and SSC9 in Duroc pig, SSC3, SSC7 and SSC18 in Landrace pig, and SSC7, SSC8 and SSC10 in Yorkshire pig. Among the markers, MARC0038565, located between the vertnin (VRTN) and synapse differentiation-inducing 1-like (SYNDIG1L) genes, showed the strongest association in the Duroc pig and was significant in all breeds. In Landrace and Yorkshire pigs, the most significant markers were located within the apoptosis resistant E3 ubiquitin protein ligase 1 (AREL1) and latent transforming growth factor beta-binding protein 2 (LTBP2) genes in SSC7, respectively. VRTN is a candidate gene regulating the teat number. Most markers were located in SSC7, indicating their significance in determining teat number and their potential as valuable genomic selection targets for improving this trait. Extensive linkage disequilibrium blocks were identified in SSC7, supporting their use in genomic selection strategies. Our study provides valuable insights into the genetic architecture of teat numbers in pigs, and helps identify candidate genes and genomic regions that may contribute to this economically important trait.

Prognostic Role of Circulating LTBP-2 in Patients With Dilated Cardiomyopathy: A Novel Biomarker Reflecting Extracellular Matrix LTBP-2 Accumulation.

Dilated cardiomyopathy (DCM) is a life-threatening disease related to heart failure. Extracellular matrix proteins have an important role in the pathogenesis of DCM. Latent transforming growth factor beta-binding protein 2 (LTBP-2), a type of extracellular matrix protein, has not been investigated in DCM. First, we compared plasma LTBP-2 levels in 131 patients with DCM who underwent endomyocardial biopsy and 44 controls who were matched for age and sex and had no cardiac abnormalities. Next, we performed immunohistochemistry for LTBP-2 on endomyocardial biopsy specimens and followed the DCM patients for ventricular assist device (VAD) implantation, cardiac death, and all-cause death. Patients with DCM had elevated plasma LTBP-2 levels compared with controls (P < 0.001). Plasma LTBP-2 levels were positively correlated with LTBP-2-positive fraction in the myocardium from the biopsy specimen. When patients with DCM were divided into 2 groups according to LTBP-2 levels, Kaplan-Meier analysis demonstrated that patients with high plasma LTBP-2 were associated with increased incidences of cardiac death/VAD and all-cause death/VAD. In addition, patients with high myocardial LTBP-2-positive fractions were associated with increased incidences of these adverse outcomes. Multivariable Cox proportional hazard analysis showed that plasma LTBP-2 and myocardial LTBP-2-positive fraction were independently associated with adverse outcomes. Circulating LTBP-2 can serve as a biomarker to predict adverse outcomes, reflecting extracellular matrix LTBP-2 accumulation in the myocardium in DCM.

Alveolar capillary dysplasia without misalignment of pulmonary veins, hyperinflammation, megalocornea and overgrowth – Association with a homozygous 2bp-insertion in LTBP2?

We present a male infant with alveolar capillary dysplasia without misalignment of pulmonary veins, hyperinflammation, megalocornea and macrosomia/macrocephaly at birth. Whole-exome sequencing revealed a homozygous 2bp-insertion in the latent transforming growth factor-beta binding protein 2 (LTBP2) (c.278_279dup, p.(Ser94Glyfs*187)). So far, LTBP2-variants have been frequently reported with an eye-restricted phenotype including primary congenital glaucoma and megalocornea/microspherphakia and ectopia lentis with/without secondary glaucoma. Hitherto reported systemic phenotypes showed, among others, features as tall stature, finger anomalies, high-arched palate and cardiovascular anomalies. The main pathophysiological finding of our patient was an alveolar capillary dysplasia (with pulmonary arterial hypertension and right ventricular impairment but without misalignment of pulmonary veins) resulting in almost continuous oxygen demand and prolonged dependence on mechanical ventilation. He died of respiratory failure at the age of seven months. This patient may extend the LTBP2-related phenotype with resulting diagnostic implications.

Latent-transforming growth factor beta-binding protein-2 (LTBP-2) is required for longevity but not for development of zonular fibers

Latent-transforming growth factor beta-binding protein 2 (LTBP-2) is a major component of arterial and lung tissue and of the ciliary zonule, the system of extracellular fibers that centers and suspends the lens in the eye. LTBP-2 has been implicated previously in the development of extracellular microfibrils, although its exact role remains unclear. Here, we analyzed the three-dimensional structure of the ciliary zonule in wild type mice and used a knockout model to test the contribution of LTBP-2 to zonule structure and mechanical properties. In wild types, zonular fibers had diameters of 0.5–1.0 micrometers, with an outer layer of fibrillin-1-rich microfibrils and a core of fibrillin-2-rich microfibrils. LTBP-2 was present in both layers. The absence of LTBP-2 did not affect the number of fibers, their diameters, nor their coaxial organization. However, by two months of age, LTBP-2-depleted fibers began to rupture, and by six months, a fully penetrant ectopia lentis phenotype was present, as confirmed by in vivo imaging. To determine whether the seemingly normal fibers of young mice were compromised mechanically, we compared zonule stress/strain relationships of wild type and LTBP-2-deficient mice and developed a quasi-linear viscoelastic engineering model to analyze the resulting data. In the absence of LTBP-2, the ultimate tensile strength of the zonule was reduced by about 50%, and the viscoelastic behavior of the fibers was altered significantly. We developed a harmonic oscillator model to calculate the forces generated during saccadic eye movement. Model simulations suggested that mutant fibers are prone to failure during rapid rotation of the eyeball. Together, these data indicate that LTBP-2 is necessary for the strength and longevity of zonular fibers, but not necessarily for their formation.

Transcriptomic Signature of Right Ventricular Failure in Experimental Pulmonary Arterial Hypertension: Deep Sequencing Demonstrates Mitochondrial, Fibrotic, Inflammatory and Angiogenic Abnormalities.

Right ventricular failure (RVF) remains the leading cause of death in pulmonary arterial hypertension (PAH). We investigated the transcriptomic signature of RVF in hemodynamically well-phenotyped monocrotaline (MCT)-treated, male, Sprague-Dawley rats with severe PAH and decompensated RVF (increased right ventricular (RV) end diastolic volume (EDV), decreased cardiac output (CO), tricuspid annular plane systolic excursion (TAPSE) and ventricular-arterial decoupling). RNA sequencing revealed 2547 differentially regulated transcripts in MCT-RVF RVs. Multiple enriched gene ontology (GO) terms converged on mitochondria/metabolism, fibrosis, inflammation, and angiogenesis. The mitochondrial transcriptomic pathway is the most affected in RVF, with 413 dysregulated genes. Downregulated genes included TFAM (−0.45-fold), suggesting impaired mitochondrial biogenesis, CYP2E1 (−3.8-fold), a monooxygenase which when downregulated increases oxidative stress, dehydrogenase/reductase 7C (DHRS7C) (−2.8-fold), consistent with excessive autonomic activation, and polypeptide N-acetyl-galactose-aminyl-transferase 13 (GALNT13), a known pulmonary hypertension (PH) biomarker (−2.7-fold). The most up-regulated gene encodes Periostin (POSTN; 4.5-fold), a matricellular protein relevant to fibrosis. Other dysregulated genes relevant to fibrosis include latent-transforming growth factor beta-binding protein 2 (LTBP2), thrombospondin4 (THBS4). We also identified one dysregulated gene relevant to all disordered transcriptomic pathways, ANNEXIN A1. This anti-inflammatory, phospholipid-binding mediator, is a putative target for therapy in RVF-PAH. Comparison of expression profiles in the MCT-RV with published microarray data from the RV of pulmonary artery-banded mice and humans with bone morphogenetic protein receptor type 2 (BMPR2)-mutations PAH reveals substantial conservation of gene dysregulation, which may facilitate clinical translation of preclinical therapeutic and biomarkers studies. Transcriptomics reveals the molecular fingerprint of RVF to be heavily characterized by mitochondrial dysfunction, fibrosis and inflammation.

Candidate Gene Analysis Identifies Mutations in CYP1B1 and LTBP2 in Indian Families with Primary Congenital Glaucoma.

Primary congenital glaucoma (PCG) is a severe ocular disorder that presents early in life. Cytochrome P4501B1 (CYP1B1) and latent transforming growth factor-beta-binding protein 2 (LTBP2) are the most commonly mutated genes in PCG. To investigate the causative genetic mutations in eight Indian families with PCG. Whole-exome sequencing was applied to analyze the genomic DNA samples from PCG probands. Sanger sequencing was utilized to confirm the identified mutations. We identified four homozygous missense mutations (c.1405C>T, p.R469W; c.1397G>T, p.G466V; c.1198C>T, p.P400S; and c.1103G>A, p.R368H) in CYP1B1 and one nonsense mutation (c.2421G>A, p.W807X) in LTBP2 in eight Indian families. Among the five mutations identified, G466V in CYP1B1 and W807X in LTBP2 represent novel mutations. Our study expands the mutational spectrum of PCG in the Indian population.

Glaucoma in iran and contributions of studies in iran to the understanding of the etiology of glaucoma.

Epidemiologic and genetic/molecular research on glaucoma in Iran started within the past decade. A population-based study on the epidemiology of glaucoma in Yazd, a city in central Iran, revealed that 4.4% of studied individuals were affected with glaucoma: 1.6% with high tension primary open angle glaucoma (POAG), 1.6% with normal tension POAG, and 0.4% each with primary angle closure glaucoma (PACG) and pseudoexfoliation glaucoma (PEXG), and other types of secondary glaucoma. Two notable observations were the relatively high frequency of normal tension glaucoma cases (1.6%) and the large fraction of glaucoma affected individuals (nearly 90%) who were unaware of their condition. The first and most subsequent genetic studies on glaucoma in Iran were focused on primary congenital glaucoma (PCG) showing that cytochrome P450 1B1 (CYP1B1) is the cause of PCG in the majority of Iranian patients, many different CYP1B1 mutations are present among Iranian patients but only four mutations constitute the vast majority, and the origins of most mutations in the Iranians are identical by descent (IBD) with the same mutations in other populations. Furthermore, most of the PCG patients are from the northern and northwestern provinces of Iran. A statistically significant male predominance of PCG was observed only among patients without CYP1B1 mutations. Clinical investigations on family members of PCG patients revealed that CYP1B1 mutations exhibit variable expressivity, but almost complete penetrance. A great number of individuals harboring CYP1B1 mutations become affected with juvenile onset POAG. Screening of JOAG patients showed that an approximately equal fraction of the patients harbor CYP1B1 and (myocilin) MYOC mutations; MYOC is a well-known adult onset glaucoma causing gene. Presence of CYP1B1 mutations in JOAG patients suggests that in some cases, the two conditions may share a common etiology. Further genetic analysis of Iranian PCG patients led to identification of Latent-transforming growth factor beta-binding protein 2 (LTBP2) as a causative gene for both PCG and several diseases which are often accompanied by glaucomatous presentations, such as Weill-Marchesani syndrome 3 (WMS3). The findings on LTBP2 have contributed to recognize the importance of the extracellular matrix in pathways leading to glaucoma.

Genetic, Biochemical and Clinical Insights into Primary Congenital Glaucoma.

ABSTRACTGlaucoma is an irreversible form of optic neuropathy in which the optic nerve suffers damage in a characteristic manner with optic nerve cupping and retinal ganglion cell death. Primary congenital glaucoma (PCG) is an idiopathic irreversible childhood blinding disorder which manifests at birth or within the first year of life. PCG presents with a classical triad of symptoms (viz epiphora, photophobia and blepharospasm) though there are many additional symptoms, including large eye ball and hazy cornea. The only anatomical anomaly found in PCG is trabecular meshwork (TM) dysgenesis. PCG is an inheritable disease with established genetic etiology. It transmits through autosomal recessive mode. A number of cases are sporadic also. Mutations in many genes have been found to be causative in PCG and many are yet to be found. Mutations in cytochrome P4501B1 (CYP1B1) gene have been found to be the predominant cause of PCG. Other genes that have been implicated in PCG etiology are myocilin, Forkhead-related transcription factor C1 (FOXC1) and latent transforming growth factor beta-binding protein 2 (LTBP2). Mutations in these genes have been reported from many parts of the world. In addition to this, mitochondrial genome mutations are also thought to be involved in its pathogenesis. There appears to be some mechanism involving more than one genetic factor. In this review, we will discuss the various clinical, biochemical and genetic aspects of PCG. We emphasize that etiology of PCG does not lie in a single gene or genetic factor. Research needs to be oriented into a direction where gene-gene interactions, ocular embryology, ophthalmic metabolism and systemic oxidative status need to be studied in order to understand this disorder. We also accentuate the need for ophthalmic genetic facilities in all ophthalmology setups.How to cite this article: Faiq M, Sharma R, Dada R, Mohanty K, Saluja D, Dada T. Genetic, Biochemical and Clinical Insights into Primary Congenital Glaucoma. J Current Glau Prac 2013;7(2):66-84.

Development of a new chick chorioallantoic membrane model for human pancreas adenocarcinoma

Pancreatic cancer is the fourth leading cause of cancer death in developed countries. Early‐stage pancreatic cancer is usually clinically silent, and disease only becomes apparent after the tumor invades surrounding tissues or metastasizes to distant organs. One of the urgent challenges in pancreas cancer research is to set up model systems allowing the development and testing of new therapies as well as the discovery of new diagnostic markers. The chick chorioallantoic membrane (CAM) has been successfully used to produce tumors from various cancer cell lines. Here, using BxPC3 human pancreatic cells we were able to produce within 7 days post‐grafting 30 mm3vascularized tumor on CAM. Histology analysis revealed that the cancer cells formed tumors compatible with PanIN‐3 grade human malignant adenocarcinomas. Immunohistochemistry revealed that the malignant cells were positive for carcinoembryonic antigen and cytokeratin‐7, and ‐19. Functional blood vessels were numerous between pancreatic islets. Interestingly, we were able to demonstrate that two biomarkers recently identified in our lab from human pancreas cancer tissues, latent‐transforming growth factor beta‐binding protein 2 (LTBP‐2) and transforming growth factor beta‐induced (TGFBI) were found to be also expressed in the BxPC3. The possibility to perfuse the tumor allows to expect this model to be used to detect new biomarkers as well as inject and test drugs.This work was support by the Fond Léon‐Fredericq (ULg) and FNRS.

A proteomic approach for identification and localization of the pericellular components of chondrocytes

Although the pericellular matrix (PCM) plays a central role in the communication between chondrocytes and extracellular matrix, its composition is largely unknown. In this study, the PCM was investigated with a proteomic approach using chondrons, which are enzymatically isolated constructs including the chondrocyte and its surrounding PCM. Chondrons and chondrocytes alone were isolated from human articular cartilage. Proteins extracted from chondrons and chondrocytes were used for two-dimensional electrophoresis. Protein spots were quantitatively compared between chondron and chondrocyte gels. Cellular proteins, which had similar density between chondron and chondrocyte gels, did not proceed for analysis. Since chondrons only differ from chondrocytes in association of the PCM, protein spots in the chondron gels that had higher quantity than that in the chondrocyte gels were selected as candidates of the PCM components and processed for mass spectrometry. Among 15 identified peptides, several were fragments of the three type VI collagen chains (α-1, α-2, and α-3). Other identified PCM proteins included triosephosphate isomerase, transforming growth factor-β induced protein, peroxiredoxin-4, ADAM (A disintegrin and metalloproteinases) 28, and latent-transforming growth factor beta-binding protein-2. These PCM components were verified with immunohisto(cyto)chemistry for localization in the PCM region of articular cartilage. The abundance of type VI collagen in the PCM emphasizes its importance to the microenvironment of chondrocytes. Several proteins were localized in the PCM of chondrocytes for the first time and that warrants further investigation for their functions in cartilage biology.

Identification of LOXL1 protein and Apolipoprotein E as components of surgically isolated pseudoexfoliation material by direct mass spectrometry

Pseudoexfoliation (PEX) syndrome is the commonest cause of secondary glaucoma. Many extracellular matrix proteins and elastic fibre structure components are present in the pathological PEX deposits in the anterior segment of the eye including the anterior lens capsule. Common coding variants in the lysyl oxidase-like 1 (LOXL1) gene, involved in cross-linking elastin, have been reported to be strongly associated with PEX syndrome in various human populations. The mechanism by which the LOXL1 protein contributes to the formation of PEX material is unknown. A comprehensive map of the component proteins of PEX deposits can aid the understanding of disease pathogenesis. The purpose of this study was to identify additional protein constituents of pathological PEX deposits. We employed a novel proteomics approach by performing mass spectrometry on “isolated” PEX material surgically removed from the anterior lens capsule of affected eyes. This approach led to the identification of LOXL1 protein and Apolipoprotein E (ApoE) in PEX material. Previously identified protein constituents, latent-transforming growth factor beta-binding protein-2, complement 3 and clusterin were also detected. Immunohistochemical analysis of lens capsules from affected eyes confirmed the presence of both LOXL1 and ApoE in pathological PEX deposits. ApoE is a novel component of these deposits. This is the first report where a direct analytical approach has led to the identification of LOXL1 in PEX deposits and is consistent with its detection in these deposits by immunolabelling in another recent report. LOXL1 is both genetically associated with PEX syndrome and present in pathological PEX deposits. Hence it clearly has an important and direct role in pathophysiology of the disease. In conclusion, additional as yet unknown components are present in pathological PEX deposits and mass spectrometry of “isolated” PEX material is an effective strategy for their identification.

Recombinant Latent Transforming Growth Factor β-binding Protein 2 Assembles to Fibroblast Extracellular Matrix and Is Susceptible to Proteolytic Processing and Release

Latent transforming growth factor beta-binding protein 2 (LTBP-2) belongs to the fibrillin-LTBP gene family and is a component of 10-nm microfibrils. LTBP-2 consists mainly of domains of 8-cysteine and EGF-like repeats linked by proline-rich regions. To characterize the biochemical properties of LTBP-2, its assembly to the extracellular matrix, and its proteolytic release from the matrix, LTBP-2 was expressed recombinantly in Chinese hamster ovary cells and purified to homogeneity under nondenaturing conditions. Purified LTBP-2 bound calcium and was glycosylated at the central domain of EGF-like repeats. Antibodies made against the recombinant LTBP-2 decorated fibrillar structures in fibroblast extracellular matrix. Treatment of matrices with plasmin or elastase released a soluble approximately 160-kDa LTBP-2 fragment. Processing of LTBP-2 was studied by treating purified LTBP-2 with plasmin or porcine pancreatic elastase. LTBP-2 was processed with these proteases initially to a approximately 160-kDa fragment, and with higher concentrations to a protease-resistant approximately 120-kDa fragment. Processing sites were localized by amino acid sequencing to proline-rich regions at the N-terminal part of LTBP-2, suggesting that the matrix binding sites locate to the N-terminal approximately 500 amino acids of LTBP-2. Purified and biotinylated LTBP-2 could be assembled to fibrillar structures in fibroblast extracellular matrix during cell cultivation, indicating that LTBP-2 assembly to the matrix is not strictly linked to cells that make it and suggesting that microfibril assembly may involve soluble intermediates.