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Frontiers in Cardiovascular Medicine 2021Recently, the extracellular matrix protein agrin has been reported to promote tumor angiogenesis that supports tumorigenesis and metastasis; however, there is a lack of...
Recently, the extracellular matrix protein agrin has been reported to promote tumor angiogenesis that supports tumorigenesis and metastasis; however, there is a lack of genetic evidence to prove whether agrin derived from the tumors or endothelial cells (ECs) systemically should be the therapeutic target. To date, the physiological role of endothelial agrin has also not been investigated. In the EC-specific agrin knockout mice, we observed normal endothelial and haematopoietic cell development during embryogenesis. Moreover, these mice develop normal vascular barrier integrity and vasoreactivity at the adult stage. Importantly, the growth of localized or metastatic cancer cells was not affected after implantation into endothelial agrin depleted mice. Mechanistically, agrin did not regulate endothelial ERK1/2, YAP or p53 activation that is central to support endothelial proliferation, survival and invasion. Cumulatively, our findings may suggest that agrin could play a redundant role in endothelial development during physiological and tumor angiogenesis. Targeting the endothelial derived agrin might not be effective in inhibiting tumor angiogenesis.
PubMed: 35174224
DOI: 10.3389/fcvm.2021.810477 -
Cell Reports Jan 2024Perlecan (HSPG2), a heparan sulfate proteoglycan similar to agrin, is key for extracellular matrix (ECM) maturation and stabilization. Although crucial for cardiac...
Perlecan (HSPG2), a heparan sulfate proteoglycan similar to agrin, is key for extracellular matrix (ECM) maturation and stabilization. Although crucial for cardiac development, its role remains elusive. We show that perlecan expression increases as cardiomyocytes mature in vivo and during human pluripotent stem cell differentiation to cardiomyocytes (hPSC-CMs). Perlecan-haploinsuffient hPSCs (HSPG2) differentiate efficiently, but late-stage CMs have structural, contractile, metabolic, and ECM gene dysregulation. In keeping with this, late-stage HSPG2 hPSC-CMs have immature features, including reduced ⍺-actinin expression and increased glycolytic metabolism and proliferation. Moreover, perlecan-haploinsuffient engineered heart tissues have reduced tissue thickness and force generation. Conversely, hPSC-CMs grown on a perlecan-peptide substrate are enlarged and display increased nucleation, typical of hypertrophic growth. Together, perlecan appears to play the opposite role of agrin, promoting cellular maturation rather than hyperplasia and proliferation. Perlecan signaling is likely mediated via its binding to the dystroglycan complex. Targeting perlecan-dependent signaling may help reverse the phenotypic switch common to heart failure.
Topics: Humans; Heparan Sulfate Proteoglycans; Agrin; Myocytes, Cardiac; Extracellular Matrix; Extracellular Matrix Proteins
PubMed: 38198277
DOI: 10.1016/j.celrep.2023.113668 -
Cell and Tissue Research Nov 2021The extracellular matrix protein Agrin has been detected in chondrocytes and endosteal osteoblasts but its function in osteoblast differentiation has not been...
The extracellular matrix protein Agrin has been detected in chondrocytes and endosteal osteoblasts but its function in osteoblast differentiation has not been investigated yet. Thus, it is possible that Agrin contributes to osteoblast differentiation and, due to Agrin and wingless-related integration site (Wnt) sharing the same receptor, transmembrane low-density lipoprotein receptor-related protein 4 (Lrp4), and the crosstalk between Wnt and bone morphogenetic protein (BMP) signalling, both pathways could be involved in this Agrin-mediated osteoblast differentiation. Confirming this, Agrin and its receptors Lrp4 and α-dystroglycan (Dag1) were expressed during differentiation of osteoblasts from three different sources. Moreover, the disruption of Agrin impaired the expression of its receptors and osteoblast differentiation, and the treatment with recombinant Agrin slightly increase this process. In addition, whilst Agrin knockdown downregulated the expression of genes related to Wnt and BMP signalling pathways, the addition of Agrin had no effect on these genes. Altogether, these data uncover the contribution of Agrin to osteoblast differentiation and suggest that, at least in part, an Agrin-Wnt-BMP circuit is involved in this process. This makes Agrin a candidate as target for developing new therapeutic strategies to treat bone-related diseases and injuries.
Topics: 3T3 Cells; Agrin; Animals; Cell Differentiation; Cells, Cultured; Gene Expression Regulation; Humans; Mice; Mice, Inbred C57BL; Osteoblasts; Osteogenesis
PubMed: 34223979
DOI: 10.1007/s00441-021-03494-9 -
Scientific Reports Aug 2023Congenital myasthenic syndromes (CMS) are a clinically and genetically heterogeneous group of rare diseases due to mutations in neuromuscular junction (NMJ)...
Congenital myasthenic syndromes (CMS) are a clinically and genetically heterogeneous group of rare diseases due to mutations in neuromuscular junction (NMJ) protein-coding genes. Until now, many mutations encoding postsynaptic proteins as Agrin, MuSK and LRP4 have been identified as responsible for increasingly complex CMS phenotypes. The majority of mutations identified in LRP4 gene causes bone diseases including CLS and sclerosteosis-2 and rare cases of CMS with mutations in LRP4 gene has been described so far. In the French cohort of CMS patients, we identified a novel LRP4 homozygous missense mutation (c.1820A > G; p.Thy607Cys) within the β1 propeller domain in a patient presenting CMS symptoms, including muscle weakness, fluctuating fatigability and a decrement in compound muscle action potential in spinal accessory nerves, associated with congenital agenesis of the hands and feet and renal malformation. Mechanistic expression studies show a significant decrease of AChR aggregation in cultured patient myotubes, as well as altered in vitro binding of agrin and Wnt11 ligands to the mutated β1 propeller domain of LRP4 explaining the dual phenotype characterized clinically and electoneuromyographically in the patient. These results expand the LRP4 mutations spectrum associated with a previously undescribed clinical association involving impaired neuromuscular transmission and limb deformities and highlighting the critical role of a yet poorly described domain of LRP4 at the NMJ. This study raises the question of the frequency of this rare neuromuscular form and the future diagnosis and management of these cases.
Topics: Humans; Myasthenic Syndromes, Congenital; Agrin; Mutation; Foot; LDL-Receptor Related Proteins
PubMed: 37640745
DOI: 10.1038/s41598-023-41008-5 -
Clinica Chimica Acta; International... Sep 2015This review describes the state of the art for the use of laboratory testing in myasthenia gravis. The review brings a detailed description of the different clinical... (Review)
Review
This review describes the state of the art for the use of laboratory testing in myasthenia gravis. The review brings a detailed description of the different clinical forms of auto-immune myasthenia and of the Lambert Eaton Myasthenic Syndrome (LEMS). They stress the differences between the different forms of acquired (auto-immune) myasthenia. Then they present a summary of the different antibodies found in the disease. They insist on the advantage of the RIPA assay to measure antibodies to the acetylcholine receptor. They stress the different types of contribution of each of these antibodies to the clinical diagnosis. They also describe the methods to measure each of the specific antibodies that have recently permitted to split the diagnosis: Abs to omega-conotoxin receptor in Lambert Eaton Myasthenic Syndrome (LEMS), abs to the acetylcholine receptor (AchR) in MG, Abs to muscle specific tyrosine kinase (MuSK) in Ab negative MG, and Abs to low molecular weight receptor related low-density lipo protein-4 (LRP-4). They also broach over the striated antibodies, less frequent and clinically less useful such as anti-titin, -ryanodine, -agrin and -rapsyn. This represent a 360° view of the field as presented in Toronto in October 2014.
Topics: Autoantibodies; Clinical Laboratory Techniques; Humans; LDL-Receptor Related Proteins; Myasthenia Gravis; Receptor Protein-Tyrosine Kinases; Receptors, Cholinergic
PubMed: 26238187
DOI: 10.1016/j.cca.2015.07.030 -
Clinica Chimica Acta; International... Apr 2015This review describes the state of the art for the use of laboratory testing in myasthenia gravis. The review brings a detailed description of the different clinical... (Review)
Review
This review describes the state of the art for the use of laboratory testing in myasthenia gravis. The review brings a detailed description of the different clinical forms of auto-immune myasthenia and of the Lambert Eaton Myasthenic Syndrome (LEMS). The stress the differences between the different forms of acquired (auto-immune) myasthenia. Then they present a summary of the different antibodies found in the disease. They insist on the advantage of the RIPA assay to measure antibodies to the acetylcholine receptor. They stress the different types of contribution of each of these antibodies to the clinical diagnosis. They also describe the methods to measure each of the specific antibodies that have recently permitted to split the diagnosis: Abs to omega-conotoxin receptor in Lambert Eaton Myasthenic Syndrome (LEMS), abs to the acetylcholine receptor (AchR) in MG, Abs to muscle specific tyrosine kinase (MuSK) in Ab negative MG, and Abs to low molecular weight receptor related low-density lipo protein-4 (LRP-4). They also broach over the striated antibodies, less frequent and clinically less useful such as anti-titin, -ryanodine, -agrin and -rapsyn. This represent a 360° view of the field as presented in Toronto in October 2014.
Topics: Antibodies; Clinical Laboratory Techniques; Humans; Myasthenia Gravis
PubMed: 25689792
DOI: 10.1016/j.cca.2015.01.042 -
International Journal of Molecular... Feb 2018The neuromuscular synapse is a relatively large synapse with hundreds of active zones in presynaptic motor nerve terminals and more than ten million acetylcholine... (Review)
Review
The neuromuscular synapse is a relatively large synapse with hundreds of active zones in presynaptic motor nerve terminals and more than ten million acetylcholine receptors (AChRs) in the postsynaptic membrane. The enrichment of proteins in presynaptic and postsynaptic membranes ensures a rapid, robust, and reliable synaptic transmission. Over fifty years ago, classic studies of the neuromuscular synapse led to a comprehensive understanding of how a synapse looks and works, but these landmark studies did not reveal the molecular mechanisms responsible for building and maintaining a synapse. During the past two-dozen years, the critical molecular players, responsible for assembling the specialized postsynaptic membrane and regulating nerve terminal differentiation, have begun to be identified and their mechanism of action better understood. Here, we describe and discuss five of these key molecular players, paying heed to their discovery as well as describing their currently understood mechanisms of action. In addition, we discuss the important gaps that remain to better understand how these proteins act to control synaptic differentiation and maintenance.
Topics: Animals; Biomarkers; Humans; LDL-Receptor Related Proteins; Muscle Proteins; Neuromuscular Junction; Receptors, Cholinergic; Synaptic Transmission
PubMed: 29415504
DOI: 10.3390/ijms19020490 -
Molecular Neurobiology Mar 2023Motor function recovery from injury requires the regeneration of not only muscle fibers, but also the neuromuscular junction-the synapse between motor nerve terminals...
Motor function recovery from injury requires the regeneration of not only muscle fibers, but also the neuromuscular junction-the synapse between motor nerve terminals and muscle fibers. However, unlike muscle regeneration which has been extensively studied, little is known about the molecular mechanisms of NMJ regeneration. Recognizing the critical role of agrin-LRP4-MuSK signaling in NMJ formation and maintenance, we investigated whether increasing MuSK activity promotes NMJ regeneration. To this end, we evaluated the effect of DOK7, a protein that stimulates MuSK, on NMJ regeneration. Reinnervation, AChR cluster density, and endplate area were improved, and fragmentation was reduced in the AAV9-DOK7-GFP-injected muscles compared with muscles injected with AAV9-GFP. These results demonstrated expedited NMJ regeneration associated with increased DOK7 expression and support the hypothesis that increasing agrin signaling benefits motor function recovery after injury. Our findings propose a potentially new therapeutic strategy for functional recovery after muscle and nerve injury, i.e., promoting NMJ regeneration by increasing agrin signaling.
Topics: Agrin; Neuromuscular Junction; Receptors, Cholinergic; Synapses; Muscle Proteins; Animals; Mice; Regeneration
PubMed: 36464749
DOI: 10.1007/s12035-022-03143-4 -
Chemico-biological Interactions Nov 2016The low-density lipoprotein receptor-related protein 4 (LRP4) and the muscle-specific receptor tyrosine kinase (MuSK) form a tetrameric protein complex on the... (Review)
Review
The low-density lipoprotein receptor-related protein 4 (LRP4) and the muscle-specific receptor tyrosine kinase (MuSK) form a tetrameric protein complex on the postsynaptic membrane at the neuromuscular junction (NMJ). Binding of agrin to LRP4 triggers phosphorylation of MuSK. Activated MuSK drives clustering of acetylcholine receptor (AChR). Wnt ligands also directly bind to MuSK to induce AChR clustering. MuSK anchors the acetylcholinesterase (AChE)/collagen Q (ColQ) complex to the synaptic basal lamina. In addition, an extracellular proteoglycan, biglycan, binds to MuSK. Anti-MuSK autoantibodies (MuSK-IgG) are observed in 5-15% of autoimmune myasthenia gravis (MG) patients. MuSK-IgG blocks both ColQ-MuSK and LRP4-MuSK interactions. MuSK-IgG, LRP4, ColQ, and biglycan bind to the immunoglobulin-like domains 1 and 4 of MuSK. Lack of the effects of cholinesterase inhibitors in MuSK-MG patients is likely due to hindrance of ColQ-MuSK interaction by MuSK-IgG and subsequent deficiency of AChE observed in model mice, which, however, has not been proven in MuSK-MG patients. As ColQ enhances expression of membrane-bound MuSK, inhibition of ColQ-MuSK interaction by MuSK-IgG may account for lack of AChR clusters in MuSK-MG. We thus made passive transfer models using Colq+/+ and Colq-/- mice to dissect the effect of ColQ on AChR clustering in MuSK-MG. We found that MuSK-IgG-mediated suppression of LRP4-MuSK interaction, not of ColQ-MuSK interaction, caused defective AChR clustering. We also unexpectedly observed that both MuSK-IgG and ColQ suppressed agrin/LRP4/MuSK signaling in dose-dependent manners. Quantitative comparison revealed that MuSK-IgG blocked agrin-LRP4-MuSK signaling more than ColQ. We propose that attenuation of AChR clustering in MuSK-MG is due to hindrance of LRP4-MuSK interaction in the presence of agrin by MuSK-IgG.
Topics: Animals; Antibodies; Collagen; Humans; Myasthenia Gravis; Neuromuscular Junction; Protein Binding; Receptor Protein-Tyrosine Kinases
PubMed: 27119269
DOI: 10.1016/j.cbi.2016.04.019 -
British Journal of Cancer Jun 2018The extracellular matrix modulates the hallmarks of cancer. Here we examined the role of agrin-a member of this matrix-in progression of oral squamous cell carcinoma...
BACKGROUND
The extracellular matrix modulates the hallmarks of cancer. Here we examined the role of agrin-a member of this matrix-in progression of oral squamous cell carcinoma (OSCC).
METHODS
We evaluated the immunohistochemical expression of agrin in OSCC and dysplasias. Benign lesions were used as control. In subsequent experiments, we investigated whether the silencing of agrin interferes with tumour expansion both in vitro as well as in vivo. To gain insights into the role of agrin, we identified its protein network (interactome) using mass spectrometry-based proteomics and bioinformatics. Finally, we evaluated the clinical relevance of agrin interactome.
RESULTS
Agrin was elevated in malignant and premalignant lesions. Further, we show that agrin silencing interferes with cancer cell motility, proliferation, invasion, colony and tumour spheroid formation, and it also reduces the phosphorylation of FAK, ERK and cyclin D1 proteins in OSCC cells. In orthotopic model, agrin silencing reduces tumour aggressiveness, like vascular and neural invasion. From a clinical perspective, agrin contextual hubs predict a poor clinical prognosis related with overall survival.
CONCLUSIONS
Altogether, our results demonstrate that agrin is a histological marker for the progression of oral cancer and is a strong therapeutic target candidate for both premalignant and OSCC lesions.
Topics: Agrin; Animals; Cell Line, Tumor; Cell Movement; Disease Progression; HEK293 Cells; Heterografts; Humans; Immunohistochemistry; Male; Mice; Mice, Inbred NOD; Mice, SCID; Mouth Mucosa; Mouth Neoplasms; Precancerous Conditions; Retrospective Studies; Squamous Cell Carcinoma of Head and Neck
PubMed: 29872149
DOI: 10.1038/s41416-018-0135-5