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Journal of Neuroimmunology Jul 2021Autoantibodies against agrin and cortactin have been described in patients with myasthenia gravis. To further validate and characterize these autoantibodies, sera and/or...
Autoantibodies against agrin and cortactin have been described in patients with myasthenia gravis. To further validate and characterize these autoantibodies, sera and/or plasma exchange material of 135 patients with myasthenia gravis were screened for anti-agrin or anti-cortactin autoantibodies. Autoantibodies against cortactin were detected in three patients and two controls and could be confirmed by cell-based assays using cortactin-transfected human embryonic kidney cells in both controls and one patient, but were not detectable in follow-up sera of the three patients. We did not detect any autoantibodies against agrin. The clinical phenotype of anti-cortactin-positive patients varied, arguing against a relevant pathogenic role.
Topics: Aged; Agrin; Autoantibodies; Biomarkers; Cortactin; Female; HEK293 Cells; Humans; Male; Middle Aged; Myasthenia Gravis
PubMed: 33962172
DOI: 10.1016/j.jneuroim.2021.577588 -
European Journal of Biochemistry Oct 1999Synapses are essential relay stations for the transmission of information between neurones and other cells. An ordered and tightly regulated formation of these... (Review)
Review
Synapses are essential relay stations for the transmission of information between neurones and other cells. An ordered and tightly regulated formation of these structures is crucial for the functioning of the nervous system. The induction of the intensively studied synapse between nerve and muscle is initiated by the binding of neurone-specific isoforms of the basal membrane protein agrin to receptors on the surface of myotubes. Agrin activates a receptor complex that includes the muscle-specific kinase and most likely additional, yet to be identified, components. Receptor activation leads to the aggregation of acetylcholine receptors (AChR) and other proteins of the postsynaptic apparatus. This activation process has unique features which distinguish it from other receptor tyrosine kinases. In particular, the autophosphorylation of the kinase domain, which usually induces the recruitment of adaptor and signalling molecules, is not sufficient for AChR aggregation. Apparently, interactions of the extracellular domain with unknown components are also required for this process. Agrin binds to a second protein complex on the muscle surface known as the dystrophin-associated glycoprotein complex. This binding forms one end of a molecular link between the extracellular matrix and the cytoskeleton. While many components of the machinery triggering postsynaptic differentiation have now been identified, our picture of the molecular pathway causing the redistribution of synaptic proteins is still incomplete.
Topics: Agrin; Cell Communication; Cytoskeletal Proteins; Dystroglycans; Membrane Glycoproteins; Motor Neurons; Muscle Proteins; Neuromuscular Junction; Protein Isoforms; Receptor Protein-Tyrosine Kinases; Receptors, Cholinergic; Receptors, Growth Factor
PubMed: 10491152
DOI: 10.1046/j.1432-1327.1999.00765.x -
Internal Medicine (Tokyo, Japan) Mar 2022The patient had suffered from both proximal and distal limb weakness since her early childhood, without the involvement of ocular or respiratory muscles. Repetitive...
The patient had suffered from both proximal and distal limb weakness since her early childhood, without the involvement of ocular or respiratory muscles. Repetitive nerve stimulation (RNS) at 3 Hz showed significant decrement in the area and amplitude of the compound muscle action potential (CMAP) on the right abductor digiti minimi (26%) and trapezius (17%). Whole-exon sequencing revealed two novel heterozygous mutations (p.Q1406Rfs*29 and p.R1521H) in the LG1 domain of agrin, which were deemed likely pathogenic for congenital myasthenic syndromes (CMS) according to a bioinformatics analysis. The patient showed remarkable improvement after treatment with salbutamol. This case expanded the mutation spectrum of AGRN.
Topics: Agrin; Child, Preschool; Exons; Female; Humans; Muscle Weakness; Mutation; Myasthenic Syndromes, Congenital
PubMed: 34433720
DOI: 10.2169/internalmedicine.7774-21 -
PloS One May 2010The C-terminal 95 kDa fragment of some isoforms of vertebrate agrins is sufficient to induce clustering of acetylcholine receptors but despite two decades of intense...
The C-terminal 95 kDa fragment of some isoforms of vertebrate agrins is sufficient to induce clustering of acetylcholine receptors but despite two decades of intense agrin research very little is known about the function of the other isoforms and the function of the larger, N-terminal part of agrins that is common to all isoforms. Since the N-terminal part of agrins contains several follistatin-domains, a domain type that is frequently implicated in binding TGFbetas, we have explored the interaction of the N-terminal part of rat agrin (Agrin-Nterm) with members of the TGFbeta family using surface plasmon resonance spectroscopy and reporter assays. Here we show that agrin binds BMP2, BMP4 and TGFbeta1 with relatively high affinity, the K(D) values of the interactions calculated from SPR experiments fall in the 10(-8) M-10(-7) M range. In reporter assays Agrin-Nterm inhibited the activities of BMP2 and BMP4, half maximal inhibition being achieved at approximately 5x10(-7) M. Paradoxically, in the case of TGFbeta1 Agrin N-term caused a slight increase in activity in reporter assays. Our finding that agrin binds members of the TGFbeta family may have important implications for the role of these growth factors in the regulation of synaptogenesis as well as for the role of agrin isoforms that are unable to induce clustering of acetylcholine receptors. We suggest that binding of these TGFbeta family members to agrin may have a dual function: agrin may serve as a reservoir for these growth factors and may also inhibit their growth promoting activity. Based on analysis of the evolutionary history of agrin we suggest that agrin's growth factor binding function is more ancient than its involvement in acetylcholine receptor clustering.
Topics: Agrin; Animals; Bone Morphogenetic Protein 2; Bone Morphogenetic Protein 4; Bone Morphogenetic Protein Receptors; Cell Line; Chromatography, Affinity; Chromatography, Gel; Evolution, Molecular; Humans; Intercellular Signaling Peptides and Proteins; Kinetics; Protein Binding; Protein Structure, Tertiary; Rats; Receptors, Transforming Growth Factor beta; Surface Plasmon Resonance; Transforming Growth Factor beta1
PubMed: 20505824
DOI: 10.1371/journal.pone.0010758 -
Polish Journal of Pathology : Official... 2019Agrin has recently been identified as a novel oncogene that is overexpressed in several types of human cancers. However, its role in lung cancer has not yet been...
Agrin has recently been identified as a novel oncogene that is overexpressed in several types of human cancers. However, its role in lung cancer has not yet been investigated. The purpose of the current study was to investigate agrin protein expression in lung cancer and evaluate its clinicopathological and prognostic significance. In this study, A total of 86 lung adenocarcinoma samples paired with adjacent non-tumour tissue samples and eight lung adenocarcinoma non-paired samples were selected for immunohistochemical staining for agrin. Strong staining of agrin in nuclei of lung adenocarcinoma tissues was observed, but not in the nuclei of normal lung tissues (p < 0.001). Consistent with staining in lung adenocarcinoma tissues, the nuclei staining of agrin was also detected in lung cancer cell lines by immunofluorescence. This is the first report demonstrating that agrin is highly expressed in nuclei of lung adenocarcinoma tissues and that it is strongly correlated with lymph node metastasis (p = 0.002), clinical stage (p = 0.024), and poor differentiation (p = 0.022). Agrin-positive nuclear staining of lung adenocarcinoma cells could be used to identify greatly increased risk of metastasis in patients after surgery, which might serve as a valuable prognostic marker.
Topics: Adenocarcinoma of Lung; Agrin; Biomarkers, Tumor; Humans; Lung Neoplasms; Lymphatic Metastasis; Neoplasm Staging; Prognosis
PubMed: 31820863
DOI: 10.5114/pjp.2019.90396 -
Scientific Reports Nov 2022SMN protein deficiency causes motoneuron disease spinal muscular atrophy (SMA). SMN-based therapies improve patient motor symptoms to variable degrees. An early hallmark...
SMN protein deficiency causes motoneuron disease spinal muscular atrophy (SMA). SMN-based therapies improve patient motor symptoms to variable degrees. An early hallmark of SMA is the perturbation of the neuromuscular junction (NMJ), a synapse between a motoneuron and muscle cell. NMJ formation depends on acetylcholine receptor (AChR) clustering triggered by agrin and its co-receptors lipoprotein receptor-related protein 4 (LRP4) and transmembrane muscle-specific kinase (MuSK) signalling pathway. We have previously shown that flunarizine improves NMJs in SMA model mice, but the mechanisms remain elusive. We show here that flunarizine promotes AChR clustering in cell-autonomous, dose- and agrin-dependent manners in C2C12 myotubes. This is associated with an increase in protein levels of LRP4, integrin-beta-1 and alpha-dystroglycan, three agrin co-receptors. Furthermore, flunarizine enhances MuSK interaction with integrin-beta-1 and phosphotyrosines. Moreover, the drug acts on the expression and splicing of Agrn and Cacna1h genes in a muscle-specific manner. We reveal that the Cacna1h encoded protein Cav3.2 closely associates in vitro with the agrin co-receptor LRP4. In vivo, it is enriched nearby NMJs during neonatal development and the drug increases this immunolabelling in SMA muscles. Thus, flunarizine modulates key players of the NMJ and identifies Ca3.2 as a new protein involved in the NMJ biology.
Topics: Animals; Mice; Agrin; Flunarizine; Integrins; Muscular Atrophy, Spinal; Neuromuscular Junction; Receptor Protein-Tyrosine Kinases; Receptors, Cholinergic
PubMed: 36347955
DOI: 10.1038/s41598-022-23703-x -
The Journal of Neuroscience : the... Dec 2000Agrin controls the formation of the neuromuscular junction. Whether it regulates the differentiation of other types of synapses remains unclear. Therefore, we have...
Agrin controls the formation of the neuromuscular junction. Whether it regulates the differentiation of other types of synapses remains unclear. Therefore, we have studied the role of agrin in cultured hippocampal neurons. Synaptogenesis was severely compromised when agrin expression or function was suppressed by antisense oligonucleotides and specific antibodies. The effects of antisense oligonucleotides were found to be highly specific because they were reversed by adding recombinant agrin and could not be detected in cultures from agrin-deficient animals. Interestingly, the few synapses formed in reduced agrin conditions displayed diminished vesicular turnover, despite a normal appearance at the EM level. Thus, our results demonstrate the necessity of agrin for synaptogenesis in hippocampal neurons.
Topics: Agrin; Animals; Antibodies; Cell Count; Cell Differentiation; Cells, Cultured; Electric Stimulation; Endocytosis; Evoked Potentials; Exocytosis; Hippocampus; Neurons; Oligonucleotides, Antisense; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Recombinant Proteins; Synapses; Synaptic Transmission; Synaptic Vesicles; Tetrodotoxin
PubMed: 11124985
DOI: 10.1523/JNEUROSCI.20-24-09086.2000 -
Development (Cambridge, England) Oct 2005The pivotal role of agrin in inducing postsynaptic specializations at neuromuscular junctions has been well characterized. Increasing evidence suggests that agrin is...
The pivotal role of agrin in inducing postsynaptic specializations at neuromuscular junctions has been well characterized. Increasing evidence suggests that agrin is also involved in neuronal development. In this study, we found that agrin inhibited neurite extension and, more importantly, a gradient of agrin induced repulsive growth-cone turning in cultured Xenopus spinal neurons. Incubation with a neutralizing antibody to agrin or expression of the extracellular domain of muscle-specific kinase, a component of the agrin receptor complex, abolished these effects of agrin. Agrin-induced repulsive growth-cone turning requires the activity of PI3-kinase and Ca2+ signaling. In addition, the expression of dominant-negative Rac1 inhibited neurite extension and blocked agrin-mediated growth-cone turning. Taken together, our findings suggest that agrin regulates neurite extension and provide evidence for an unanticipated role of agrin in growth-cone steering in developing neurons.
Topics: Agrin; Animals; Calcium Signaling; Cells, Cultured; Embryo, Nonmammalian; Growth Cones; Motor Neurons; Neurites; Phosphatidylinositol 3-Kinases; Spinal Cord; Xenopus laevis; rac1 GTP-Binding Protein
PubMed: 16141222
DOI: 10.1242/dev.02016 -
The Journal of Comparative Neurology Feb 2020The basement membrane that seperates the endothelial cells and astrocytic endfeet that comprise the blood-brain barrier is rich in collagen, laminin, agrin, and...
The basement membrane that seperates the endothelial cells and astrocytic endfeet that comprise the blood-brain barrier is rich in collagen, laminin, agrin, and perlecan. Previous studies have demonstrated that the proper recruitment of the water-permeable channel aquaporin-4 (AQP4) to astrocytic endfeet is dependent on interactions between laminin and the receptor dystroglycan. In this study, we conducted a deeper investigation into how the basement membrane might further regulate the expression, localization, and function of AQP4, using primary astrocytes as a model system. We found that treating these cells with laminin causes endogenous agrin to localize to the cell surface, where it co-clusters with β-dystroglycan (β-DG). Conversely, agrin sliencing profoundly disrupts β-DG clustering. As in the case of laminin111, Matrigel™, a complete basement membrane analog, also causes the clustering of AQP4 and β-DG. This clustering, whether induced by laminin111 or Matrigel™ is inhibited when the astrocytes are first incubated with an antibody against the γ1 subunit of laminin, suggesting that the latter is crucial to the process. Finally, we showed that laminin111 appears to negatively regulate AQP4-mediated water transport in astrocytes, suppressing the cell swelling that occurs following a hypoosmotic challenge. This suppression is abolished if DG expression is silenced, again demonstrating the central role of this receptor in relaying the effects of laminin.
Topics: Agrin; Animals; Aquaporin 4; Astrocytes; Cells, Cultured; Laminin; Mice; Rats; Rats, Sprague-Dawley
PubMed: 31454080
DOI: 10.1002/cne.24763 -
Annual Review of Neuroscience 1995
Review
Topics: Agrin; Alternative Splicing; Animals; Cell Differentiation; Central Nervous System; Neuromuscular Junction; Receptors, Growth Factor; Synapses
PubMed: 7605069
DOI: 10.1146/annurev.ne.18.030195.002303