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https://www.readbyqxmd.com/read/26355076/collagen-q-and-anti-musk-autoantibody-competitively-suppress-agrin-lrp4-musk-signaling
#1
Kenji Otsuka, Mikako Ito, Bisei Ohkawara, Akio Masuda, Yu Kawakami, Ko Sahashi, Hiroshi Nishida, Naoki Mabuchi, Akemi Takano, Andrew G Engel, Kinji Ohno
MuSK antibody-positive myasthenia gravis (MuSK-MG) accounts for 5 to 15% of autoimmune MG. MuSK and LRP4 are coreceptors for agrin in the signaling pathway that causes clustering of acetylcholine receptor (AChR). MuSK also anchors the acetylcholinesterase (AChE)/collagen Q (ColQ) complex to the synaptic basal lamina. We previously reported that anti-MuSK antibodies (MuSK-IgG) block binding of ColQ to MuSK and cause partial endplate AChE deficiency in mice. We here analyzed the physiological significance of binding of ColQ to MuSK and block of this binding by MuSK-IgG...
2015: Scientific Reports
https://www.readbyqxmd.com/read/26284792/flow-cytofluorimetric-analysis-of-anti-lrp4-ldl-receptor-related-protein-4-autoantibodies-in-italian-patients-with-myasthenia-gravis
#2
COMPARATIVE STUDY
Mariapaola Marino, Flavia Scuderi, Daniela Samengo, Giorgia Saltelli, Maria Teresa Maiuri, Chengyong Shen, Lin Mei, Mario Sabatelli, Giovambattista Pani, Giovanni Antonini, Amelia Evoli, Emanuela Bartoccioni
BACKGROUND: Myasthenia gravis (MG) is an autoimmune disease in which 90% of patients have autoantibodies against the muscle nicotinic acetylcholine receptor (AChR), while autoantibodies to muscle-specific tyrosine kinase (MuSK) have been detected in half (5%) of the remaining 10%. Recently, the low-density lipoprotein receptor-related protein 4 (LRP4), identified as the agrin receptor, has been recognized as a third autoimmune target in a significant portion of the double sero-negative (dSN) myasthenic individuals, with variable frequency depending on different methods and origin countries of the tested population...
2015: PloS One
https://www.readbyqxmd.com/read/26238187/an-update-on-laboratory-diagnosis-in-myasthenia-gravis
#3
REVIEW
Joel Oger, Hans Frykman
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...
September 20, 2015: Clinica Chimica Acta; International Journal of Clinical Chemistry
https://www.readbyqxmd.com/read/25689792/an-update-on-laboratory-diagnosis-in-myasthenia-gravis
#4
REVIEW
Joel Oger, Hans Frykman
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...
April 15, 2015: Clinica Chimica Acta; International Journal of Clinical Chemistry
https://www.readbyqxmd.com/read/25483608/expression-identification-and-biological-effects-of-the-novel-recombination-protein-pacap38-nta-with-high-bioactivity
#5
Lusheng Wu, Jing Wang, Xiaojia Chen, An Hong
Pituitary adenylate cyclase‑activating polypeptide (PACAP) is a type of neuropeptide with multiple biological functions. However, it has a short half‑life period in the body, ~3 to 5 min, restricting its further development as a drug that can promote the recovery of nerve injury. In vitro and in vivo experiments have shown that PACAP can repair the epithelial cell on the surface of the injured cornea, as PACAP can act on the trigeminal nerve cell to secrete other active neurotransmitters, which can promote corneal epithelial cell proliferation and differentiation...
February 2015: International Journal of Molecular Medicine
https://www.readbyqxmd.com/read/25404300/disruption-of-lrp4-function-by-genetic-deletion-or-pharmacological-blockade-increases-bone-mass-and-serum-sclerostin-levels
#6
Ming-Kang Chang, Ina Kramer, Thomas Huber, Bernd Kinzel, Sabine Guth-Gundel, Olivier Leupin, Michaela Kneissel
We identified previously in vitro LRP4 (low-density lipoprotein receptor-related protein 4) as a facilitator of the WNT (Wingless-type) antagonist sclerostin and found mutations disrupting this function to be associated with high bone mass in humans similar to patients lacking sclerostin. To further delineate the role of LRP4 in bone in vivo, we generated mice lacking Lrp4 in osteoblasts/osteocytes or osteocytes only. Lrp4 deficiency promoted progressive cancellous and cortical bone gain in both mutants, although more pronouncedly in mice deficient in osteoblast/osteocyte Lrp4, consistent with our observation in human bone that LRP4 is most strongly expressed by osteoblasts and early osteocytes...
December 2, 2014: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/25137515/what-s-in-the-literature
#7
David Lacomis, Nicholas J Silvestri, Gil I Wolfe
In this issue, we review recent reports of anti-agrin antibodies as a cause of myasthenia gravis (MG) and of the clinical and electrophysiologic responses to acetylcholinesterase inhibitors in muscle specific kinase (MuSK) MG. We highlight recommendations from a working group in the United Kingdom regarding pregnancy and MG and review a report of the use of maintenance plasma exchange and intravenous immunoglobulin in juvenile MG. Regarding articles on peripheral neuropathy, there is a recent report of inflammatory neuropathy after hip surgery and a review of transthyretin amyloidosis...
September 2014: Journal of Clinical Neuromuscular Disease
https://www.readbyqxmd.com/read/24800501/-autoantibodies-detected-in-acetylcholine-receptor-antibody-negative-myasthenia-gravis
#8
REVIEW
Rie Ohta, Masakatsu Motomura
Myasthenia gravis (MG) is caused by the failure of neuromuscular transmission mediated by pathogenic autoantibodies (Abs) against the acetylcholine receptor (AChR), muscle-specific receptor tyrosine kinase (MuSK), and unknown autoantibodies. The seropositivity rates for routine AChR binding Ab and MuSK Ab in MG are 85% and a few % for MG patients in Japan, respectively. The autoimmune target in the remaining patients is unknown. In 2001, Hoch et al. reported that a proportion of AChR-Ab-negative MG patients had serum IgG antibodies against MuSK, shedding new light on the pathogenesis of the disease...
March 2014: Rinsho Byori. the Japanese Journal of Clinical Pathology
https://www.readbyqxmd.com/read/24793185/anti-agrin-autoantibodies-in-myasthenia-gravis
#9
Christiane Gasperi, Arthur Melms, Benedikt Schoser, Yina Zhang, Julia Meltoranta, Valerie Risson, Laurent Schaeffer, Bertold Schalke, Stephan Kröger
OBJECTIVE: Because the extracellular matrix protein agrin is essential for neuromuscular junction formation and maintenance, we tested the hypothesis that autoantibodies against agrin are present in sera from patients with myasthenia gravis (MG). METHODS: We determined the presence of anti-agrin antibodies in 54 sera from patients with generalized MG using a solid-phase ELISA with purified mini-agrin protein. Thirty of the 54 sera were seronegative for antibodies against the acetylcholine receptor (AChR) or muscle-specific tyrosine kinase (MuSK), 15 had elevated levels of anti-MuSK, and 9 had elevated levels of anti-AChR autoantibodies...
June 3, 2014: Neurology
https://www.readbyqxmd.com/read/24587270/crosslinking-induced-endocytosis-of-acetylcholine-receptors-by-quantum-dots
#10
Chi Wai Lee, Hailong Zhang, Lin Geng, H Benjamin Peng
In a majority of patients with myasthenia gravis (MG), anti-acetylcholine receptor (AChR) antibodies target postsynaptic AChR clusters and thus compromise the membrane integrity of neuromuscular junctions (NMJs) and lead to muscle weakness. Antibody-induced endocytosis of AChRs in the postsynaptic membrane represents the initial step in the pathogenesis of MG; however, the molecular mechanisms underlying AChR endocytosis remain largely unknown. Here, we developed an approach to mimic the pathogenic antibodies for inducing the crosslinking and internalization of AChRs from the postsynaptic membrane...
2014: PloS One
https://www.readbyqxmd.com/read/24244707/musk-myasthenia-gravis-igg4-disrupts-the-interaction-of-lrp4-with-musk-but-both-igg4-and-igg1-3-can-disperse-preformed-agrin-independent-achr-clusters
#11
Inga Koneczny, Judith Cossins, Patrick Waters, David Beeson, Angela Vincent
A variable proportion of patients with generalized myasthenia gravis (MG) have autoantibodies to muscle specific tyrosine kinase (MuSK). During development agrin, released from the motor nerve, interacts with low density lipoprotein receptor-related protein-4 (LRP4), which then binds to MuSK; MuSK interaction with the intracellular protein Dok7 results in clustering of the acetylcholine receptors (AChRs) on the postsynaptic membrane. In mature muscle, MuSK helps maintain the high density of AChRs at the neuromuscular junction...
2013: PloS One
https://www.readbyqxmd.com/read/24200689/antibodies-against-low-density-lipoprotein-receptor-related-protein-4-induce-myasthenia-gravis
#12
Chengyong Shen, Yisheng Lu, Bin Zhang, Dwight Figueiredo, Jonathan Bean, Jiung Jung, Haitao Wu, Arnab Barik, Dong-Min Yin, Wen-Cheng Xiong, Lin Mei
Myasthenia gravis (MG) is the most common disorder affecting the neuromuscular junction (NMJ). MG is frequently caused by autoantibodies against acetylcholine receptor (AChR) and a kinase critical for NMJ formation, MuSK; however, a proportion of MG patients are double-negative for anti-AChR and anti-MuSK antibodies. Recent studies in these subjects have identified autoantibodies against low-density lipoprotein receptor-related protein 4 (LRP4), an agrin receptor also critical for NMJ formation. LRP4 autoantibodies have not previously been implicated in MG pathogenesis...
December 2013: Journal of Clinical Investigation
https://www.readbyqxmd.com/read/24145553/vascular-delivery-of-raavrh74-mck-galgt2-to-the-gastrocnemius-muscle-of-the-rhesus-macaque-stimulates-the-expression-of-dystrophin-and-laminin-%C3%AE-2-surrogates
#13
Louis G Chicoine, Louise R Rodino-Klapac, Guohong Shao, Rui Xu, William G Bremer, Marybeth Camboni, Bethannie Golden, Chrystal L Montgomery, Kimberly Shontz, Kristin N Heller, Danielle A Griffin, Sarah Lewis, Brian D Coley, Christopher M Walker, K Reed Clark, Zarife Sahenk, Jerry R Mendell, Paul T Martin
Overexpression of GALGT2 in skeletal muscle can stimulate the glycosylation of α dystroglycan and the upregulation of normally synaptic dystroglycan-binding proteins, some of which are dystrophin and laminin α2 surrogates known to be therapeutic for several forms of muscular dystrophy. This article describes the vascular delivery of GALGT2 gene therapy in a large animal model, the rhesus macaque. Recombinant adeno-associated virus, rhesus serotype 74 (rAAVrh74), was used to deliver GALGT2 via the femoral artery to the gastrocnemius muscle using an isolated focal limb perfusion method...
April 2014: Molecular Therapy: the Journal of the American Society of Gene Therapy
https://www.readbyqxmd.com/read/23777098/-novel-autoantibodies-in-myasthenia-gravis
#14
REVIEW
Akiko Nagaishi, Waka Sakai, Masakatsu Motomura
Patients with myasthenia gravis(MG) are divided into three groups: (1) acetylcholine receptor antibody positive MG: 80%, (2) muscle-specific receptor tyrosine kinase (MuSK) antibody positive MG: 5-10%, and (3) double seronegative MG. In 2011, autoantibodies (Abs) against low-density lipoprotein receptor-related protein 4(Lrp4) were identified in Japanese MG patients and thereafter have been reported in Germany and USA. In other Lrp4 Ab papers, Lrp4 Ab positive sera inhibited agrin-induced aggregation of AChRs in cultured myotubes, suggesting a pathogenic role regarding the dysfunction of the neuromuscular endplate...
May 2013: Nihon Rinsho. Japanese Journal of Clinical Medicine
https://www.readbyqxmd.com/read/23535159/the-different-roles-of-the-thymus-in-the-pathogenesis-of-the-various-myasthenia-gravis-subtypes
#15
Alexander Marx, Frederick Pfister, Berthold Schalke, Güher Saruhan-Direskeneli, Arthur Melms, Philipp Ströbel
The thymus plays distinct roles in the pathogenesis of the different Myasthenia gravis (MG) subtypes. Inflammatory, neoplastic and age-related alterations of the thymus are of pivotal relevance for the initiation of anti-acetylcholine receptor (AChR) autoimmunity in early onset MG, thymoma-associated MG and, likely, late onset MG, respectively. By contrast, the thymus is presumably not related to MG that is due to autoantibodies to the muscle specific kinase, MuSK. Finally, the role of the thymus is still obscure in MG defined by antibodies against the agrin receptor LRP4 and in MG without all of the above autoantibdies (triple sero-negative MG) since these MG subtypes have been described only recently and thymectomy has not been their standard treatment...
July 2013: Autoimmunity Reviews
https://www.readbyqxmd.com/read/23252893/structure-of-the-neuromuscular-junction-function-and-cooperative-mechanisms-in-the-synapse
#16
REVIEW
Masaharu Takamori
As an overview of the structure of the neuromuscular junction, three items are described focusing on cooperative mechanisms involving the synapse and leading to muscle contraction: (1) presynaptic acetylcholine release regulated by vesicle cycling (exocytosis and endocytosis); the fast-mode of endocytosis requires a large influx of external Ca(2+) and is promoted by the activation of G protein-coupled receptors and receptor tyrosine kinases; (2) postsynaptic acetylcholine receptor clustering mediated by the muscle-specific, Dok7-stimulated tyrosine kinase (MuSK) through two signaling mechanisms: one via agrin-Lrp4-MuSK (Ig1/2 domains) and the second via Wnt-MuSK (Frizzled-like cysteine-rich domain)-adaptor Dishevelled; Wnts/MuSK and Lrp4 direct a retrograde signal to presynaptic differentiation; (3) muscle contractile machinery regulated by Ca(2+) -release and Ca(2+) -influx channels, including the depolarization-activated ryanodine receptor-1 and the receptor- and/or store-operated transient receptor potential canonical...
December 2012: Annals of the New York Academy of Sciences
https://www.readbyqxmd.com/read/23196600/-anti-musk-antibodies-in-myasthenia-gravis-block-binding-of-collagen-q-to-musk
#17
Kinji Ohno
In myasthenia gravis (MG), 5-15% of patients are positive for MuSK antibodies. MuSK binds to LRP4 and transmits an agrin-mediated signal for clustering of acetylcholine receptor (AChR). MuSK also anchors the collagenic tail subunit (ColQ) of acetylcholinesterase (AChE). MuSK-IgG is a blocking antibody, but its molecular targets remained elusive. As acetylcholine receptor (AChR) deficiency is typically mild and as cholinesterase inhibitors are generally ineffective in MuSK-MG patients, we asked if MuSK-IgG interferes with binding of ColQ to MuSK...
2012: Rinshō Shinkeigaku, Clinical Neurology
https://www.readbyqxmd.com/read/23196599/-progress-of-myasthenia-gravis-discovery-of-lrp4-antibodies
#18
Masakatsu Motomura, Osamu Higuchi
Myasthenia gravis (MG) is caused by the failure of neuromuscular transmission mediated by pathogenic autoantibodies (Abs) against acetylcholine receptor (AChR) and muscle-specific receptor tyrosine kinase (MuSK). The seropositivity rates for routine AChR binding Ab and MuSK Ab in MG are 80-85% and 5-10% for MG patients in Japan, respectively. The autoimmune target in the remaining patients is unknown. In 2011, autoantibodies against low-density lipoprotein receptor-related protein 4 (Lrp4) were identified in Japanese MG patients and thereafter have been reported in Germany and the USA...
2012: Rinshō Shinkeigaku, Clinical Neurology
https://www.readbyqxmd.com/read/22999188/antibodies-against-wnt-receptor-of-muscle-specific-tyrosine-kinase-in-myasthenia-gravis
#19
Masaharu Takamori, Tatsufumi Nakamura, Masakatsu Motomura
Muscle-specific tyrosine kinase (MuSK) antibodies are detected in a proportion of myasthenia gravis (MG) patients who are negative for acetylcholine receptor (AChR) antibodies and have prominent bulbar weakness and crises. In the MuSK ectodomains, the immunoglobulin-like 1 and 2 domains (Ig1/2) mediate the agrin-Lrp4-MuSK signaling and the cysteine-rich domain (CRD) mediates the Wnt-MuSK-Dishevelled signaling; both contribute to AChR clustering. Immunoblotting against recombinant proteins showed MuSK Ig1/2 antibodies in 33 anti-AChR-negative MG patients; 10 patients of them (30%) were additionally positive for MuSK CRD antibodies...
January 15, 2013: Journal of Neuroimmunology
https://www.readbyqxmd.com/read/22683512/c-terminal-agrin-fragment-as-a-potential-marker-for-sarcopenia-caused-by-degeneration-of-the-neuromuscular-junction
#20
RANDOMIZED CONTROLLED TRIAL
M Drey, C C Sieber, J M Bauer, W Uter, P Dahinden, R G Fariello, J W Vrijbloed
INTRODUCTION: Sarcopenia is considered to be an enormous burden for both the individuals affected and for society at large. A multifactorial aetiology of this geriatric syndrome has been discussed. Amongst other pathomechanisms, the degeneration of the neuromuscular junction (NMJ) may be of major relevance. The intact balance between the pro-synaptic agent agrin and the anti-synaptic agent neurotrypsin ensures a structurally and functionally intact NMJ. Excessive cleavage of the native motoneuron-derived agrin by neurotrypsin into a C-terminal Agrin Fragment (CAF) leads to functional disintegration at the NMJ and may consecutively cause sarcopenia...
January 2013: Experimental Gerontology
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