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Cellular and Molecular Life Sciences :... Jan 2016As the primary protective barrier for neurons in the brain, the blood-brain barrier (BBB) exists between the blood microcirculation system and the brain parenchyma. The... (Review)
Review
As the primary protective barrier for neurons in the brain, the blood-brain barrier (BBB) exists between the blood microcirculation system and the brain parenchyma. The normal BBB integrity is essential in protecting the brain from systemic toxins and maintaining the necessary level of nutrients and ions for neuronal function. This integrity is mediated by structural BBB components, such as tight junction proteins, integrins, annexins, and agrin, of a multicellular system including endothelial cells, astrocytes, pericytes, etc. BBB dysfunction is a significant contributor to the pathogeneses of a variety of brain disorders. Many signaling factors have been identified to be able to control BBB permeability through regulating the structural components. Among those signaling factors are inflammatory mediators, free radicals, vascular endothelial growth factor, matrix metalloproteinases, microRNAs, etc. In this review, we provide a summary of recent progress regarding these structural components and signaling factors, relating to their roles in various brain disorders. Attention is also devoted to recent research regarding impact of pharmacological agents such as isoflurane on BBB permeability and how iron ion passes across BBB. Hopefully, a better understanding of the factors controlling BBB permeability helps develop novel pharmacological interventions of BBB hyperpermeability under pathological conditions.
Topics: Agrin; Anesthetics; Animals; Annexins; Blood-Brain Barrier; Brain Diseases; Capillary Permeability; Cytokines; Eicosanoids; Humans; Integrins; Iron; MicroRNAs; Platelet Endothelial Cell Adhesion Molecule-1; Receptor-Like Protein Tyrosine Phosphatases, Class 3; Signal Transduction; Tight Junction Proteins
PubMed: 26403789
DOI: 10.1007/s00018-015-2050-8 -
Nature Cell Biology Nov 2020Dystrophin proteomic regulation in muscular dystrophies (MDs) remains unclear. We report that a long noncoding RNA (lncRNA), H19, associates with dystrophin and inhibits...
Dystrophin proteomic regulation in muscular dystrophies (MDs) remains unclear. We report that a long noncoding RNA (lncRNA), H19, associates with dystrophin and inhibits E3-ligase-dependent polyubiquitination at Lys 3584 (referred to as Ub-DMD) and its subsequent protein degradation. In-frame deletions in BMD and a DMD non-silent mutation (C3340Y) resulted in defects in the ability of the protein to interact with H19, which caused elevated Ub-DMD levels and dystrophin degradation. Dmd C3333Y mice exhibited progressive MD, elevated serum creatine kinase, heart dilation, blood vessel irregularity and respiratory failure with concurrently reduced dystrophin and increased Ub-DMD status. H19 RNA oligonucleotides conjugated with agrin (AGR-H19) and nifenazone competed with or inhibited TRIM63. Dmd C3333Y animals, induced-pluripotent-stem-cell-derived skeletal muscle cells from patients with Becker MD and mdx mice subjected to exon skipping exhibited inhibited dystrophin degradation, preserved skeletal and cardiac muscle histology, and improved strength and heart function following AGR-H19 or nifenazone treatment. Our study paves the way for meaningful targeted therapeutics for Becker MD and for certain patients with Duchenne MD.
Topics: Animals; Antipyrine; Cardiomyopathies; Cell Line; Disease Models, Animal; Dystrophin; Enzyme Inhibitors; Female; Half-Life; Humans; Induced Pluripotent Stem Cells; Male; Mice, Inbred C57BL; Mice, Inbred mdx; Mice, Mutant Strains; Muscle Proteins; Muscle Strength; Muscle, Skeletal; Muscular Dystrophies; Mutation; Myocytes, Cardiac; Niacinamide; Oligonucleotides; Protein Stability; Proteolysis; RNA, Long Noncoding; Tripartite Motif Proteins; Ubiquitin-Protein Ligases; Ubiquitination
PubMed: 33106653
DOI: 10.1038/s41556-020-00595-5 -
Journal of Cachexia, Sarcopenia and... Apr 2023Ageing is accompanied by an inexorable loss of muscle mass and functionality and represents a major risk factor for numerous diseases such as cancer, diabetes and... (Review)
Review
Ageing is accompanied by an inexorable loss of muscle mass and functionality and represents a major risk factor for numerous diseases such as cancer, diabetes and cardiovascular and pulmonary diseases. This progressive loss of muscle mass and function may also result in the insurgence of a clinical syndrome termed sarcopenia, exacerbated by inactivity and disease. Sarcopenia and muscle weakness yield the risk of falls and injuries, heavily impacting on health and social costs. Thus, screening, monitoring and prevention of conditions inducing muscle wasting and weakness are essential to improve life quality in the ageing modern society. To this aim, the reliability of easily accessible and non-invasive blood-derived biomarkers is being evaluated. C-terminal agrin fragment (CAF) has been widely investigated as a neuromuscular junction (NMJ)-related biomarker of muscle dysfunction. This narrative review summarizes and critically discusses, for the first time, the studies measuring CAF concentration in young and older, healthy and diseased individuals, cross-sectionally and in response to inactivity and physical exercise, providing possible explanations behind the discrepancies observed in the literature. To identify the studies investigating CAF in the above-mentioned conditions, all the publications found in PubMed, written in English and measuring this biomarker in blood from 2013 (when CAF was firstly measured in human serum) to 2022 were included in this review. CAF increases with age and in sarcopenic individuals when compared with age-matched, non-sarcopenic peers. In addition, CAF was found to be higher than controls in other muscle wasting conditions, such as diabetes, COPD, chronic heart failure and stroke, and in pancreatic and colorectal cancer cachectic patients. As agrin is also expressed in kidney glomeruli, chronic kidney disease and transplantation were shown to have a profound impact on CAF independently from muscle wasting. CAF concentration raises following inactivity and seems to be lowered or maintained by exercise training. Finally, CAF was reported to be cross-sectionally correlated to appendicular lean mass, handgrip and gait speed; whether longitudinal changes in CAF are associated with those in muscle mass or performance following physical exercise is still controversial. CAF seems a reliable marker to assess muscle wasting in ageing and disease, also correlating with measurements of appendicular lean mass and muscle function. Future research should aim at enlarging sample size and accurately reporting the medical history of each patient, to normalize for any condition, including chronic kidney disease, that may influence the circulating concentration of this biomarker.
Topics: Humans; Sarcopenia; Agrin; Hand Strength; Reproducibility of Results; Muscular Atrophy; Biomarkers; Renal Insufficiency, Chronic; Muscles
PubMed: 36772862
DOI: 10.1002/jcsm.13189 -
International Journal of Molecular... Apr 2017In the neuromuscular junction, postsynaptic nicotinic acetylcholine receptor (nAChR) clustering, trans-synaptic communication and synaptic stabilization are modulated by... (Review)
Review
In the neuromuscular junction, postsynaptic nicotinic acetylcholine receptor (nAChR) clustering, trans-synaptic communication and synaptic stabilization are modulated by the molecular mechanisms underlying synaptic plasticity. The synaptic functions are based presynaptically on the active zone architecture, synaptic vesicle proteins, Ca channels and synaptic vesicle recycling. Postsynaptically, they are based on rapsyn-anchored nAChR clusters, localized sensitivity to ACh, and synaptic stabilization via linkage to the extracellular matrix so as to be precisely opposed to the nerve terminal. Focusing on neural agrin, Wnts, muscle-specific tyrosine kinase (a mediator of agrin and Wnts signalings and regulator of trans-synaptic communication), low-density lipoprotein receptor-related protein 4 (the receptor of agrin and Wnts and participant in retrograde signaling), laminin-network (including muscle-derived agrin), extracellular matrix proteins (participating in the synaptic stabilization) and presynaptic receptors (including muscarinic and adenosine receptors), we review the functional structures of the synapse by making reference to immunological pathogenecities in postsynaptic disease, myasthenia gravis. The synapse-related proteins including cortactin, coronin-6, caveolin-3, doublecortin, R-spondin 2, amyloid precursor family proteins, glia cell-derived neurotrophic factor and neurexins are also discussed in terms of their possible contribution to efficient synaptic transmission at the neuromuscular junction.
Topics: Animals; Humans; LDL-Receptor Related Proteins; Neuromuscular Junction Diseases; Receptors, Muscarinic; Receptors, Nicotinic; Receptors, Purinergic P1; Synapses
PubMed: 28441759
DOI: 10.3390/ijms18040896 -
Scientific Reports Feb 2022Trk-fused gene (TFG) mutations have been identified in patients with several neurodegenerative diseases. In this study, we attempted to clarify the effects of TFG...
Trk-fused gene (TFG) mutations have been identified in patients with several neurodegenerative diseases. In this study, we attempted to clarify the effects of TFG deletions in motor neurons and in muscle fibers, using tissue-specific TFG knockout (vMNTFG KO and MUSTFG KO) mice. vMNTFG KO, generated by crossing TFG floxed with VAChT-Cre, showed deterioration of motor function and muscle atrophy especially in slow-twitch soleus muscle, in line with the predominant Cre expression in slow-twitch fatigue-resistant (S) and fast-twitch fatigue-resistant (FR) motor neurons. Consistently, denervation of the neuromuscular junction (NMJ) was apparent in the soleus, but not in the extensor digitorum longus, muscle. Muscle TFG expressions were significantly downregulated in vMNTFG KO, presumably due to decreased muscle IGF-1 concentrations. However, interestingly, MUSTFG KO mice showed no apparent impairment of muscle movements, though a denervation marker, AChRγ, was elevated and Agrin-induced AChR clustering in C2C12 myotubes was inhibited. Our results clarify that loss of motor neuron TFG is sufficient for the occurrence of NMJ degeneration and muscle atrophy, though lack of muscle TFG may exert an additional effect. Reduced muscle TFG, also observed in aged mice, might be involved in age-related NMJ degeneration, and this issue merits further study.
Topics: Animals; Humans; Insulin-Like Growth Factor I; Mice; Mice, Knockout; Motor Neurons; Muscle, Skeletal; Muscular Atrophy; Neurodegenerative Diseases; Neuromuscular Junction; Receptor, trkA
PubMed: 35121777
DOI: 10.1038/s41598-022-05884-7 -
Cell Regeneration (London, England) Jun 2019This review deals with the human adult cardiomyocyte proliferation as a potential source for heart repair after injury. The mechanism to regain the proliferative... (Review)
Review
This review deals with the human adult cardiomyocyte proliferation as a potential source for heart repair after injury. The mechanism to regain the proliferative capacity of adult cardiomyocytes is a challenge. However, recent studies are promising in showing that the 'locked' cell cycle of adult cardiomyocytes could be released through modulation of cell cycle checkpoints. In support of this are the signaling pathways of Notch, Hippo, Wnt, Akt and Jak/Stat that facilitate or inhibit the transition at cell cycle checkpoints. Cyclins and cyclin dependant kinases (CDKs) facilitate this transition which in turn is regulated by inhibitory action of pocket protein e.g. p21, p27 and p57. Transcription factors e.g. E2F, GATA4, TBx20 up regulate Cyclin A, A2, D, E, and CDK4 as promoters of cell cycle and Meis-1 and HIF-1 alpha down regulate cyclin D and E to inhibit the cell cycle. Paracrine factors like Neuregulin-1, IGF-1 and Oncostatin M and Extracellular Matrix proteins like Agrin have been involved in cardiomyocyte proliferation and dedifferentiation processes. A molecular switch model is proposed that transforms the post mitotic cell into an actively dividing cell. This model shows how the cell cycle is regulated through on- and off switch mechanisms through interaction of transcription factors and signaling pathways with proteins of the cell cycle checkpoints. Signals triggered by injury may activate the right combination of the various pathways that can 'switch on' the proliferation signals leading to myocardial regeneration.
PubMed: 31205684
DOI: 10.1016/j.cr.2018.11.002 -
Neurology Sep 2021To determine whether human anti-LRP4/agrin antibodies are pathogenic in mice and to investigate underpinning pathogenic mechanisms.
BACKGROUND AND OBJECTIVE
To determine whether human anti-LRP4/agrin antibodies are pathogenic in mice and to investigate underpinning pathogenic mechanisms.
METHODS
Immunoglobulin (Ig) was purified from a patient with myasthenia gravis (MG) with anti-LRP4/agrin antibodies and transferred to mice. Mice were characterized for body weight, muscle strength, twitch and tetanic force, neuromuscular junction (NMJ) functions including compound muscle action potential (CMAP) and endplate potentials, and NMJ structure. Effects of the antibodies on agrin-elicited muscle-specific tyrosine kinase (MuSK) activation and AChR clustering were studied and the epitopes of these antibodies were identified.
RESULTS
Patient Ig-injected mice had MG symptoms, including weight loss and muscle weakness. Decreased CMAPs, reduced twitch and tetanus force, compromised neuromuscular transmission, and NMJ fragmentation and distortion were detected in patient Ig-injected mice. Patient Ig inhibited agrin-elicited MuSK activation and AChR clustering. The patient Ig recognized the β3 domain of LRP4 and the C-terminus of agrin and reduced agrin-enhanced LRP4-MuSK interaction.
DISCUSSION
Anti-LRP4/agrin antibodies in the patient with MG is pathogenic. It impairs the NMJ by interrupting agrin-dependent LRP4-MuSK interaction.
Topics: Agrin; Animals; Antibodies; Humans; LDL-Receptor Related Proteins; Mice; Myasthenia Gravis; Neuromuscular Junction
PubMed: 34233932
DOI: 10.1212/WNL.0000000000012463 -
Gut Jan 2022Intratumor heterogeneity drives cancer progression and therapy resistance. However, it has yet to be determined whether and how subpopulations of cancer cells interact...
OBJECTIVE
Intratumor heterogeneity drives cancer progression and therapy resistance. However, it has yet to be determined whether and how subpopulations of cancer cells interact and how this interaction affects the tumour.
DESIGN
We have studied the spontaneous flow of extracellular vesicles (EVs) between subpopulations of cancer cells: cancer stem cells (CSC) and non-stem cancer cells (NSCC). To determine the biological significance of the most frequent communication route, we used pancreatic ductal adenocarcinoma (PDAC) orthotopic models, patient-derived xenografts (PDXs) and genetically engineered mouse models (GEMMs).
RESULTS
We demonstrate that PDAC tumours establish an organised communication network between subpopulations of cancer cells using EVs called the EVNet). The EVNet is plastic and reshapes in response to its environment. Communication within the EVNet occurs preferentially from CSC to NSCC. Inhibition of this communication route by impairing Rab27a function in orthotopic xenographs, GEMMs and PDXs is sufficient to hamper tumour growth and phenocopies the inhibition of communication in the whole tumour. Mechanistically, we provide evidence that CSC EVs use agrin protein to promote Yes1 associated transcriptional regulator (YAP) activation via LDL receptor related protein 4 (LRP-4). Ex vivo treatment of PDXs with antiagrin significantly impairs proliferation and decreases the levels of activated YAP.Patients with high levels of agrin and low inactive YAP show worse disease-free survival. In addition, patients with a higher number of circulating agrin EVs show a significant increased risk of disease progression.
CONCLUSION
PDAC tumours establish a cooperation network mediated by EVs that is led by CSC and agrin, which allows tumours to adapt and thrive. Targeting agrin could make targeted therapy possible for patients with PDAC and has a significant impact on CSC that feeds the tumour and is at the centre of therapy resistance.
PubMed: 35012996
DOI: 10.1136/gutjnl-2021-324994 -
Matrix Biology : Journal of the... Aug 2023During ageing, the glomerular and tubular basement membranes (BM) of the kidney undergo a progressive decline in function that is underpinned by histological changes,...
During ageing, the glomerular and tubular basement membranes (BM) of the kidney undergo a progressive decline in function that is underpinned by histological changes, including glomerulosclerosis and tubular interstitial fibrosis and atrophy. This BM-specific ageing is thought to result from damage accumulation to long-lived extracellular matrix (ECM) protein structures. Determining which BM proteins are susceptible to these structure-associated changes, and the possible mechanisms and downstream consequences, is critical to understand age-related kidney degeneration and to identify markers for therapeutic intervention. Peptide location fingerprinting (PLF) is an emerging proteomic mass spectrometry analysis technique capable of identifying ECM proteins with structure-associated differences that may occur by damage modifications in ageing. Here, we apply PLF as a bioinformatic screening tool to identify BM proteins with structure-associated differences between young and aged human glomerular and tubulointerstitial compartments. Several functional regions within key BM components displayed alterations in tryptic peptide yield, reflecting potential age-dependent shifts in molecular (e.g. laminin-binding regions in agrin) and cellular (e.g. integrin-binding regions in laminins 521 and 511) interactions, oxidation (e.g. collagen IV) and the fragmentation and release of matrikines (e.g. canstatin and endostatin from collagens IV and XVIII). Furthermore, we found that periostin and the collagen IV α2 chain exhibited structure-associated differences in ageing that were conserved between human kidney and previously analysed mouse lung, revealing BM components that harbour shared susceptibilities across species and organs.
Topics: Mice; Animals; Humans; Aged; Proteomics; Basement Membrane; Kidney; Extracellular Matrix Proteins; Collagen Type IV; Laminin; Kidney Diseases
PubMed: 37437747
DOI: 10.1016/j.matbio.2023.07.001 -
Neurology(R) Neuroimmunology &... Nov 2023Up to 50% of patients with myasthenia gravis (MG) without acetylcholine receptor antibodies (AChR-Abs) have antibodies to muscle-specific kinase (MuSK). Most MuSK...
BACKGROUND AND OBJECTIVES
Up to 50% of patients with myasthenia gravis (MG) without acetylcholine receptor antibodies (AChR-Abs) have antibodies to muscle-specific kinase (MuSK). Most MuSK antibodies (MuSK-Abs) are IgG4 and inhibit agrin-induced MuSK phosphorylation, leading to impaired clustering of AChRs at the developing or mature neuromuscular junction. However, IgG1-3 MuSK-Abs also exist in MuSK-MG patients, and their potential mechanisms have not been explored fully.
METHODS
C2C12 myotubes were exposed to MuSK-MG plasma IgG1-3 or IgG4, with or without purified agrin. MuSK, Downstream of Kinase 7 (DOK7), and βAChR were immunoprecipitated and their phosphorylation levels identified by immunoblotting. Agrin and agrin-independent AChR clusters were measured by immunofluorescence and AChR numbers by binding of I-α-bungarotoxin. Transcriptomic analysis was performed on treated myotubes.
RESULTS
IgG1-3 MuSK-Abs impaired AChR clustering without inhibiting agrin-induced MuSK phosphorylation. Moreover, the well-established pathway initiated by MuSK through DOK7, resulting in βAChR phosphorylation, was not impaired by MuSK-IgG1-3 and was agrin-independent. Nevertheless, the AChR clusters did not form, and both the number of AChR microclusters that precede full cluster formation and the myotube surface AChRs were reduced. Transcriptomic analysis did not throw light on the pathways involved. However, the SHP2 inhibitor, NSC-87877, increased the number of microclusters and led to fully formed AChR clusters.
DISCUSSION
MuSK-IgG1-3 is pathogenic but seems to act through a noncanonical pathway. Further studies should throw light on the mechanisms involved at the neuromuscular junction.
Topics: Humans; Agrin; Immunoglobulin G; Muscle Proteins; Myasthenia Gravis; Phosphorylation; Receptor Protein-Tyrosine Kinases; Receptors, Cholinergic
PubMed: 37582613
DOI: 10.1212/NXI.0000000000200147