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Davis-Anderson K, Micheva-Viteva S, Solomon E, Hovde B, Cirigliano E, Harris J, Twary S, Iyer R. CRISPR/Cas9 Directed Reprogramming of iPSC for Accelerated Motor Neuron Differentiation Leads to Dysregulation of Neuronal Fate Patterning and Function. Int J Mol Sci 2023; 24:16161. [PMID: 38003351 PMCID: PMC10671572 DOI: 10.3390/ijms242216161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 10/26/2023] [Accepted: 11/02/2023] [Indexed: 11/26/2023] Open
Abstract
Neurodegeneration causes a significant disease burden and there are few therapeutic interventions available for reversing or slowing the disease progression. Induced pluripotent stem cells (iPSCs) hold significant potential since they are sourced from adult tissue and have the capacity to be differentiated into numerous cell lineages, including motor neurons. This differentiation process traditionally relies on cell lineage patterning factors to be supplied in the differentiation media. Genetic engineering of iPSC with the introduction of recombinant master regulators of motor neuron (MN) differentiation has the potential to shorten and streamline cell developmental programs. We have established stable iPSC cell lines with transient induction of exogenous LHX3 and ISL1 from the Tet-activator regulatory region and have demonstrated that induction of the transgenes is not sufficient for the development of mature MNs in the absence of neuron patterning factors. Comparative global transcriptome analysis of MN development from native and Lhx-ISL1 modified iPSC cultures demonstrated that the genetic manipulation helped to streamline the neuronal patterning process. However, leaky gene expression of the exogenous MN master regulators in iPSC resulted in the premature activation of genetic pathways characteristic of the mature MN function. Dysregulation of metabolic and regulatory pathways within the developmental process affected the MN electrophysiological responses.
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Affiliation(s)
- Katie Davis-Anderson
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA; (K.D.-A.); (E.S.)
| | - Sofiya Micheva-Viteva
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA; (K.D.-A.); (E.S.)
| | - Emilia Solomon
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA; (K.D.-A.); (E.S.)
| | - Blake Hovde
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA; (K.D.-A.); (E.S.)
| | - Elisa Cirigliano
- Department of Psychology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Jennifer Harris
- Information Systems and Modeling Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA
| | - Scott Twary
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA; (K.D.-A.); (E.S.)
| | - Rashi Iyer
- Physical Chemistry and Applied Spectroscopy, Los Alamos National Laboratory, Los Alamos, NM 87544, USA
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2
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Mice deficient in synaptic protease neurotrypsin show impaired spaced long-term potentiation and blunted learning-induced modulation of dendritic spines. Cell Mol Life Sci 2023; 80:82. [PMID: 36871239 PMCID: PMC9986217 DOI: 10.1007/s00018-023-04720-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 01/21/2023] [Accepted: 02/06/2023] [Indexed: 03/06/2023]
Abstract
Neurotrypsin (NT) is a neuronal trypsin-like serine protease whose mutations cause severe mental retardation in humans. NT is activated in vitro by Hebbian-like conjunction of pre- and postsynaptic activities, which promotes the formation of dendritic filopodia via proteolytic cleavage of the proteoglycan agrin. Here, we investigated the functional importance of this mechanism for synaptic plasticity, learning, and extinction of memory. We report that juvenile neurotrypsin-deficient (NT-/-) mice exhibit impaired long-term potentiation induced by a spaced stimulation protocol designed to probe the generation of new filopodia and their conversion into functional synapses. Behaviorally, juvenile NT-/- mice show impaired contextual fear memory and have a sociability deficit. The latter persists in aged NT-/- mice, which, unlike juvenile mice, show normal recall but impaired extinction of contextual fear memories. Structurally, juvenile mutants exhibit reduced spine density in the CA1 region, fewer thin spines, and no modulation in the density of dendritic spines following fear conditioning and extinction in contrast to wild-type littermates. The head width of thin spines is reduced in both juvenile and aged NT-/- mice. In vivo delivery of adeno-associated virus expressing an NT-generated fragment of agrin, agrin-22, but not a shorter agrin-15, elevates the spine density in NT-/- mice. Moreover, agrin-22 co-aggregates with pre- and postsynaptic markers and increases the density and size of presynaptic boutons and presynaptic puncta, corroborating the view that agrin-22 supports the synaptic growth.
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Song I, Kuznetsova T, Baidoe-Ansah D, Mirzapourdelavar H, Senkov O, Hayani H, Mironov A, Kaushik R, Druzin M, Johansson S, Dityatev A. Heparan Sulfates Regulate Axonal Excitability and Context Generalization through Ca 2+/Calmodulin-Dependent Protein Kinase II. Cells 2023; 12:cells12050744. [PMID: 36899880 PMCID: PMC10000602 DOI: 10.3390/cells12050744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 02/21/2023] [Accepted: 02/23/2023] [Indexed: 03/03/2023] Open
Abstract
Our previous studies demonstrated that enzymatic removal of highly sulfated heparan sulfates with heparinase 1 impaired axonal excitability and reduced expression of ankyrin G at the axon initial segments in the CA1 region of the hippocampus ex vivo, impaired context discrimination in vivo, and increased Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity in vitro. Here, we show that in vivo delivery of heparinase 1 in the CA1 region of the hippocampus elevated autophosphorylation of CaMKII 24 h after injection in mice. Patch clamp recording in CA1 neurons revealed no significant heparinase effects on the amplitude or frequency of miniature excitatory and inhibitory postsynaptic currents, while the threshold for action potential generation was increased and fewer spikes were generated in response to current injection. Delivery of heparinase on the next day after contextual fear conditioning induced context overgeneralization 24 h after injection. Co-administration of heparinase with the CaMKII inhibitor (autocamtide-2-related inhibitory peptide) rescued neuronal excitability and expression of ankyrin G at the axon initial segment. It also restored context discrimination, suggesting the key role of CaMKII in neuronal signaling downstream of heparan sulfate proteoglycans and highlighting a link between impaired CA1 pyramidal cell excitability and context generalization during recall of contextual memories.
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Affiliation(s)
- Inseon Song
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Tatiana Kuznetsova
- Department of Integrative Medical Biology, Umeå University, 90187 Umeå, Sweden
| | - David Baidoe-Ansah
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Hadi Mirzapourdelavar
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Oleg Senkov
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Hussam Hayani
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Andrey Mironov
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Rahul Kaushik
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Michael Druzin
- Department of Integrative Medical Biology, Umeå University, 90187 Umeå, Sweden
| | - Staffan Johansson
- Department of Integrative Medical Biology, Umeå University, 90187 Umeå, Sweden
| | - Alexander Dityatev
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
- Medizinische Fakultät, Otto-von-Güricke-Universität Magdeburg, 39120 Magdeburg, Germany
- Center for Behavioral Brain Sciences (CBBS), 39106 Magdeburg, Germany
- Correspondence: ; Tel.: +49-391-67-24526; Fax: +49-391-6724530
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4
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Eldridge SE, Barawi A, Wang H, Roelofs AJ, Kaneva M, Guan Z, Lydon H, Thomas BL, Thorup AS, Fernandez BF, Caxaria S, Strachan D, Ali A, Shanmuganathan K, Pitzalis C, Whiteford JR, Henson F, McCaskie AW, De Bari C, Dell'Accio F. Agrin induces long-term osteochondral regeneration by supporting repair morphogenesis. Sci Transl Med 2020; 12:12/559/eaax9086. [PMID: 32878982 DOI: 10.1126/scitranslmed.aax9086] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 04/03/2020] [Accepted: 08/13/2020] [Indexed: 12/11/2022]
Abstract
Cartilage loss leads to osteoarthritis, the most common cause of disability for which there is no cure. Cartilage regeneration, therefore, is a priority in medicine. We report that agrin is a potent chondrogenic factor and that a single intraarticular administration of agrin induced long-lasting regeneration of critical-size osteochondral defects in mice, with restoration of tissue architecture and bone-cartilage interface. Agrin attracted joint resident progenitor cells to the site of injury and, through simultaneous activation of CREB and suppression of canonical WNT signaling downstream of β-catenin, induced expression of the chondrogenic stem cell marker GDF5 and differentiation into stable articular chondrocytes, forming stable articular cartilage. In sheep, an agrin-containing collagen gel resulted in long-lasting regeneration of bone and cartilage, which promoted increased ambulatory activity. Our findings support the therapeutic use of agrin for joint surface regeneration.
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Affiliation(s)
- Suzanne E Eldridge
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK.
| | - Aida Barawi
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Hui Wang
- Arthritis and Regenerative Medicine Laboratory, Aberdeen Centre for Arthritis and Musculoskeletal Health, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - Anke J Roelofs
- Arthritis and Regenerative Medicine Laboratory, Aberdeen Centre for Arthritis and Musculoskeletal Health, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - Magdalena Kaneva
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Zeyu Guan
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Helen Lydon
- Division of Trauma and Orthopaedic Surgery, Department of Surgery, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QQ, UK
| | - Bethan L Thomas
- Centre for Biochemical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Anne-Sophie Thorup
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Beatriz F Fernandez
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Sara Caxaria
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Danielle Strachan
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Ahmed Ali
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Kanatheepan Shanmuganathan
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Costantino Pitzalis
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - James R Whiteford
- Comparative Musculoskeletal Biology Group, Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK
| | - Frances Henson
- Centre for Microvascular Research, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK
| | - Andrew W McCaskie
- Division of Trauma and Orthopaedic Surgery, Department of Surgery, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QQ, UK
| | - Cosimo De Bari
- Arthritis and Regenerative Medicine Laboratory, Aberdeen Centre for Arthritis and Musculoskeletal Health, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - Francesco Dell'Accio
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK.
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Tsilibary E, Tzinia A, Radenovic L, Stamenkovic V, Lebitko T, Mucha M, Pawlak R, Frischknecht R, Kaczmarek L. Neural ECM proteases in learning and synaptic plasticity. PROGRESS IN BRAIN RESEARCH 2014; 214:135-57. [PMID: 25410356 DOI: 10.1016/b978-0-444-63486-3.00006-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Recent studies implicate extracellular proteases in synaptic plasticity, learning, and memory. The data are especially strong for such serine proteases as thrombin, tissue plasminogen activator, neurotrypsin, and neuropsin as well as matrix metalloproteinases, MMP-9 in particular. The role of those enzymes in the aforementioned phenomena is supported by the experimental results on the expression patterns (at the gene expression and protein and enzymatic activity levels) and functional studies, including knockout mice, specific inhibitors, etc. Counterintuitively, the studies have shown that the extracellular proteolysis is not responsible mainly for an overall degradation of the extracellular matrix (ECM) and loosening perisynaptic structures, but rather allows for releasing signaling molecules from the ECM, transsynaptic proteins, and latent form of growth factors. Notably, there are also indications implying those enzymes in the major neuropsychiatric disorders, probably by contributing to synaptic aberrations underlying such diseases as schizophrenia, bipolar, autism spectrum disorders, and drug addiction.
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Affiliation(s)
- Effie Tsilibary
- Institute of Biosciences and Applications, NCSR "Demokritos", Athens, Greece
| | - Athina Tzinia
- Institute of Biosciences and Applications, NCSR "Demokritos", Athens, Greece
| | - Lidija Radenovic
- Center for Laser Microscopy, Institute for Physiology and Biochemistry, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Vera Stamenkovic
- Center for Laser Microscopy, Institute for Physiology and Biochemistry, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Tomasz Lebitko
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw, Poland
| | | | | | - Renato Frischknecht
- Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Leszek Kaczmarek
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw, Poland.
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Kirshenbaum GS, Clapcote SJ, Petersen J, Vilsen B, Ralph MR, Roder JC. Genetic suppression of agrin reduces mania-like behavior in Na+ , K+ -ATPase α3 mutant mice. GENES BRAIN AND BEHAVIOR 2012; 11:436-43. [PMID: 22520507 DOI: 10.1111/j.1601-183x.2012.00800.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Myshkin mice heterozygous for an inactivating mutation in the neuron-specific Na(+) ,K(+) -ATPase α3 isoform show behavior analogous to mania, including an abnormal endogenous circadian period. Agrin is a proteoglycan implicated as a regulator of synapses that has been proposed to inhibit activity of Na(+) ,K(+) -ATPase α3. We examined whether the mania-related behavior of Myshkin mice could be rescued by a reduction in the expression of agrin through genetic knockout. The suppression of agrin reduced hyperambulation and holeboard exploration, restored anxiety-like behavior (or reduced risk-taking behavior), improved prepulse inhibition and shortened the circadian period. Hence, agrin is important for regulating mania-like behavior and circadian rhythms. In Myshkin mice, the suppression of agrin increased brain Na(+) ,K(+) -ATPase activity by 11 ± 4%, whereas no effect on Na(+) ,K(+) -ATPase activity was detected when agrin was suppressed in mice without the Myshkin mutation. These results introduce agrin as a potential therapeutic target for the treatment of mania and other neurological disorders associated with reduced Na(+) ,K(+) -ATPase activity and neuronal hyperexcitability.
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Affiliation(s)
- G S Kirshenbaum
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital Institute of Medical Science, University of Toronto, Toronto, ON, Canada.
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7
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Rimer M. Emerging roles for MAP kinases in agrin signaling. Commun Integr Biol 2011; 4:143-6. [PMID: 21655426 DOI: 10.4161/cib.4.2.14357] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 12/02/2010] [Indexed: 11/19/2022] Open
Abstract
Information between neurons and the target cells they innervate passes through sites of functional contact called synapses. How synapses form and are altered by sensory or cognitive experience is central to understand nervous system function. Studies of synapse formation and plasticity have concentrated on a few "model" synapses. The vertebrate neuromuscular junction (NMJ), the synapse between a motoneuron in the spinal cord and a skeletal muscle fiber, is one such model synapse. The extracellular matrix proteoglycan agrin plays an essential organizing role at the NMJ. Agrin is also present at some synapses in the brain and in other organs in the periphery, but its function outside the NMJ is unclear. The core signaling pathway for agrin at the NMJ, which is still incompletely defined, includes molecules specifically involved in this cascade and molecules used in other signaling pathways in many cells. Mitogen-activated protein kinases (MAPKs) are evolutionarily conserved components of intracellular signaling modules that control a myriad of cellular processes. This article reviews emerging evidence that suggests that MAPKs are involved in agrin signaling at the NMJ and in the putative functions of agrin in the formation of a subset of synapses in the brain.
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Affiliation(s)
- Mendell Rimer
- Department of Neuroscience & Experimental Therapeutics; College of Medicine; Texas A&M Health Science Center; College Station, TX USA
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Jayakar SS, Margiotta JF. Abelson family tyrosine kinases regulate the function of nicotinic acetylcholine receptors and nicotinic synapses on autonomic neurons. Mol Pharmacol 2011; 80:97-109. [PMID: 21502378 DOI: 10.1124/mol.111.071308] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Abelson family kinases (AFKs; Abl1, Abl2) are non-receptor tyrosine kinases (NRTKs) implicated in cancer, but they also have important physiological roles that include regulating synaptic structure and function. Recent studies using Abl-deficient mice and the antileukemia drug STI571 [imatinib mesylate (Gleevec); Novartis], which potently and selectively blocks Abl kinase activity, implicate AFKs in regulating presynaptic neurotransmitter release in hippocampus and postsynaptic clustering of nicotinic acetylcholine receptors (nAChRs) in muscle. Here, we tested whether AFKs are relevant for regulating nAChRs and nAChR-mediated synapses on autonomic neurons. AFK immunoreactivity was detected in ciliary ganglion (CG) lysates and neurons, and STI571 application blocked endogenous Abl tyrosine kinase activity. With similar potency, STI571 specifically reduced whole-cell current responses generated by both nicotinic receptor subtypes present on CG neurons (α3*- and α7-nAChRs) and lowered the frequency and amplitude of α3*-nAChR-mediated excitatory postsynaptic currents. Quantal analysis indicated that the synaptic perturbations were postsynaptic in origin, and confocal imaging experiments revealed they were unaccompanied by changes in nAChR clustering or alignment with presynaptic terminals. The results indicate that in autonomic neurons, Abl kinase activity normally supports postsynaptic nAChR function to sustain nAChR-mediated neurotransmission. Such consequences contrast with the influence of Abl kinase activity on presynaptic function and synaptic structure in hippocampus and muscle, respectively, demonstrating a cell-specific mechanism of action. Finally, because STI571 potently inhibits Abl kinase activity, the autonomic dysfunction side effects associated with its use as a chemotherapeutic agent may result from perturbed α3*- and/or α7-nAChR function.
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Affiliation(s)
- Selwyn S Jayakar
- Department of Neurosciences, University of Toledo College of Medicine, Toledo, Ohio 43614-5804, USA
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Abstract
The elusiveness of neuropathic pain mechanisms is a major impediment in developing effective clinical treatments. Here we show that peripheral nerve injury decreased agrin expression in the ipsilateral spinal dorsal horn of rats displaying tactile allodynia. SCP1, an acetaminophen analog, suppressed allodynia and promoted agrin upregulation. Preemptive treatment with SCP1 also upregulated agrin, thereby preventing neuropathic pain development. Expression of 50 kDa agrin delivered by adeno-associated virus into the dorsal horn also suppressed allodynia and hyperalgesia. Allodynia suppression was a consequence of serine residue 896/897 phosphorylation of NMDA receptor NR1 subunits in the GABA interneurons of the dorsal horn. Agrin silencing by small interference RNA, administered with either AAV-Ag50 vector or SCP1, blocked allodynia suppression, agrin upregulation, and NR1 phosphorylation. In conclusion, 50 kDa agrin modulates neuropathic pain through NR1 phosphorylation in GABA neurons. This mechanism may open new approaches for treating not only neuropathic pain, but also epilepsy, tremors, and spasticity.
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New insights into the regulation of ion channels by integrins. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 279:135-90. [PMID: 20797679 DOI: 10.1016/s1937-6448(10)79005-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
By controlling cell adhesion to the extracellular matrix, integrin receptors regulate processes as diverse as cell migration, proliferation, differentiation, apoptosis, and synaptic stability. Because the underlying mechanisms are generally accompanied by changes in transmembrane ion flow, a complex interplay occurs between integrins, ion channels, and other membrane transporters. This reciprocal interaction regulates bidirectional signal transduction across the cell surface and may take place at all levels of control, from transcription to direct conformational coupling. In particular, it is becoming increasingly clear that integrin receptors form macromolecular complexes with ion channels. Besides contributing to the membrane localization of the channel protein, the integrin/channel complex can regulate a variety of downstream signaling pathways, centered on regulatory proteins like tyrosine kinases and small GTPases. In turn, the channel protein usually controls integrin activation and expression. We review some recent advances in the field, with special emphasis on hematology and neuroscience. Some oncological implications are also discussed.
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11
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Morini R, Becchetti A. Integrin receptors and ligand-gated channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 674:95-105. [PMID: 20549943 DOI: 10.1007/978-1-4419-6066-5_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Plastic expression of different integrin subunits controls the different stages of neural development, whereas in the adult integrins regulate synaptic stability. Evidence of integrin-channel crosstalk exists for ionotropic glutamate receptors. As is often the case in other tissues, integrin engagement regulates channel activity through complex signaling pathways that often include tyrosine phosphorylation cascades. The specific pathways recruited by integrin activation depend on cerebral region and cell type. In turn, ion channels control integrin expression onto the plasma membrane and their ligand binding affinity. The most extensive studies concern the hippocampus and suggest implications for neuronal circuit plasticity. The physiological relevance of these findings depends on whether adhesion molecules, aside from determining tissue stability, contribute to synaptogenesis and the responsiveness of mature synapses, thus contributing to long-term circuit consolidation. Little evidence is available for other ligand-gated channels, with the exception of nicotinic receptors. These exert a variety of functions in neurons and non neural tissue, both in development and in the adult, by regulating cell cycle, synaptogenesis and synaptic circuit refinement. Detailed studies in epidermal keratinocytes have shed some light on the possible mechanisms through which ACh can regulate cell motility, which may be of general relevance for morphogenetic processes. As to the control of mature synapses, most results concern the integrinic control of nicotinic receptors in the neuromuscular junction. Following this lead, a few studies have addressed similar topics in adult cerebral synapses. However, pursuing and interpreting these results in the brain is especially difficult because of the complexity of the nicotinic roles and the widespread contribution of nonsynaptic, paracrine transmission. From a pathological point of view, considering the well-known contribution of both integrins and ligand-gated channels to synaptogenesis and neural regeneration, the above studies point to interesting implications for epileptogenesis.
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Affiliation(s)
- Raffaella Morini
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milano, Italy
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12
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Hilgenberg LGW, Pham B, Ortega M, Walid S, Kemmerly T, O'Dowd DK, Smith MA. Agrin regulation of alpha3 sodium-potassium ATPase activity modulates cardiac myocyte contraction. J Biol Chem 2009; 284:16956-16965. [PMID: 19376779 DOI: 10.1074/jbc.m806855200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Drugs that inhibit Na,K-ATPases, such as digoxin and ouabain, alter cardiac myocyte contractility. We recently demonstrated that agrin, a protein first identified at the vertebrate neuromuscular junction, binds to and regulates the activity of alpha3 subunit-containing isoforms of the Na,K-ATPase in the mammalian brain. Both agrin and the alpha3 Na,K-ATPase are expressed in heart, but their potential for interaction and effect on cardiac myocyte function was unknown. Here we show that agrin binds to the alpha3 subunit of the Na,K-ATPase in cardiac myocyte membranes, inducing tyrosine phosphorylation and inhibiting activity of the pump. Agrin also triggers a rapid increase in cytoplasmic Na(+) in cardiac myocytes, suggesting a role in cardiac myocyte function. Consistent with this hypothesis, spontaneous contraction frequencies of cultured cardiac myocytes prepared from mice in which agrin expression is blocked by mutation of the Agrn gene are significantly higher than in the wild type. The Agrn mutant phenotype is rescued by acute treatment with recombinant agrin. Furthermore, exposure of wild type myocytes to an agrin antagonist phenocopies the Agrn mutation. These data demonstrate that the basal frequency of myocyte contraction depends on endogenous agrin-alpha3 Na,K-ATPase interaction and suggest that agrin modulation of the alpha3 Na,K-ATPase is important in regulating heart function.
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Affiliation(s)
| | - Bryan Pham
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697
| | - Maria Ortega
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697; Developmental and Cell Biology, University of California, Irvine, California 92697
| | - Saif Walid
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697
| | - Thomas Kemmerly
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697; Developmental and Cell Biology, University of California, Irvine, California 92697
| | - Diane K O'Dowd
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697; Developmental and Cell Biology, University of California, Irvine, California 92697
| | - Martin A Smith
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697.
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Ramseger R, White R, Kröger S. Transmembrane form agrin-induced process formation requires lipid rafts and the activation of Fyn and MAPK. J Biol Chem 2009; 284:7697-705. [PMID: 19139104 DOI: 10.1074/jbc.m806719200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Overexpression or clustering of the transmembrane form of the extracellular matrix heparan sulfate proteoglycan agrin (TM-agrin) induces the formation of highly dynamic filopodia-like processes on axons and dendrites from central and peripheral nervous system-derived neurons. Here we show that the formation of these processes is paralleled by a partitioning of TM-agrin into lipid rafts, that lipid rafts and transmembrane-agrin colocalize on the processes, that extraction of lipid rafts with methyl-beta-cyclodextrin leads to a dose-dependent reduction of process formation, that inhibition of lipid raft synthesis prevents process formation, and that the continuous presence of lipid rafts is required for the maintenance of the processes. Association of TM-agrin with lipid rafts results in the phosphorylation and activation of the Src family kinase Fyn and subsequently in the phosphorylation and activation of MAPK. Inhibition of Fyn or MAPK activation inhibits process formation. These results demonstrate that the formation of filopodia-like processes by TM-agrin is the result of the activation of a complex intracellular signaling cascade, supporting the hypothesis that TM-agrin is a receptor or coreceptor on neurons.
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Affiliation(s)
- Rene Ramseger
- Department of Physiological Chemistry, University of Mainz, 55128 Mainz, Germany
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14
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Abstract
The heparan sulfate proteoglycan agrin is best known for its essential role during formation, maintenance and regeneration of the neuromuscular junction. Mutations in agrin-interacting proteins are the genetic basis for a number of neuromuscular disorders. However, agrin is widely expressed in many tissues including neurons and glial cells of the brain, where its precise function is much less understood. Fewer synapses develop in brains that lack agrin, consistent with a function of agrin during CNS synaptogenesis. Recently, a specific transmembrane form of agrin (TM-agrin) was identified that is concentrated at that interneuronal synapses in the brain. Clustering or overexpression of TM-agrin leads to the formation of filopodia-like processes, which might be precursors for CNS synapses. Agrin is subject to defined and activity-dependent proteolytic cleavage by neurotrypsin at synapses and dysregulation of agrin processing might contribute to the development of mental retardation. This review summarizes what is known about the role of agrin during synapse formation at the neuromuscular junction and in the developing CNS and will discuss additional functions of agrin in the adult CNS, in particular during BBB formation, during recovery after traumatic brain injury and in the etiology of diseases, including Alzheimer’s disease and mental retardation.
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Affiliation(s)
- Stephan Kröger
- Department of Physiological Genomics, Ludwig-Maximilians University, Schillerstrasse 46, D-80336 Munich, Germany
| | - Heike Pfister
- Department of Physiological Genomics, Ludwig-Maximilians University, Schillerstrasse 46, D-80336 Munich, Germany
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15
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Chiamulera C, Di Chio M, Tedesco V, Cantù C, Formaggio E, Fumagalli G. Nicotine-induced phosphorylation of phosphorylated cyclic AMP response element-binding protein (pCREB) in hippocampal neurons is potentiated by agrin. Neurosci Lett 2008; 442:234-8. [PMID: 18639611 DOI: 10.1016/j.neulet.2008.07.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2007] [Revised: 07/01/2008] [Accepted: 07/03/2008] [Indexed: 11/16/2022]
Abstract
The scope of this study was to test whether increased levels of the extracellular matrix molecule (ECM) agrin might enhance nicotine effects on those molecular mechanisms that initiate neuroadaptative processes in the hippocampus, a key brain area for learning and memory. We studied the effects of repetitive applications of neuronal agrin to primary hippocampal cell culture on nicotine-induced phosphorylated cyclic AMP response element-binding protein (pCREB) expression, a marker of neuroadaptation, by using immunofluorescence-based assessment of pCREB-positive neurons. We also tested agrin effects on nicotine-induced expression of a marker of metabolic activation, the immediate early gene c-fos. Agrin was shown to significantly enhance nicotine-induced pCREB, but not c-fos, expression. By using Western blotting analysis, cumulative agrin has been shown to increase nicotine-induced pCREB phosphorylation. These analyses, however, showed that inhibition of the CaMKII pathway blocked general pCREB phosphorylation, whereas inhibition of the MAPK pathway potentiated the synergistic effect of cumulative agrin and nicotine. These findings suggest that increasing the concentration of an ECM molecule, i.e. agrin, may enhance nicotine effects on pCREB and that both MAPK and CaMKII signalling may play a regulatory role.
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Affiliation(s)
- Christian Chiamulera
- Section of Pharmacology, Department of Medicine and Public Health, University of Verona, P.le Scuro, 10, 37134 Verona, Italy.
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16
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Williams S, Ryan C, Jacobson C. Agrin and neuregulin, expanding roles and implications for therapeutics. Biotechnol Adv 2008; 26:187-201. [DOI: 10.1016/j.biotechadv.2007.11.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 11/21/2007] [Accepted: 11/21/2007] [Indexed: 01/15/2023]
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17
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Lin CY, Hilgenberg LGW, Smith MA, Lynch G, Gall CM. Integrin regulation of cytoplasmic calcium in excitatory neurons depends upon glutamate receptors and release from intracellular stores. Mol Cell Neurosci 2008; 37:770-80. [PMID: 18289871 DOI: 10.1016/j.mcn.2008.01.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 11/27/2007] [Accepted: 01/03/2008] [Indexed: 01/12/2023] Open
Abstract
Integrins regulate cytoplasmic calcium levels ([Ca(2+)]i) in various cell types but information on activities in neurons is limited. The issue is of current interest because of the evidence that both integrins and changes in [Ca(2+)]i are required for Long-Term Potentiation. Accordingly, the present studies evaluated integrin ligand effects in cortical neurons. Integrin ligands or alpha5beta1 integrin activating antisera rapidly increased [Ca(2+)]i with effects greater in glutamatergic than GABAergic neurons, absent in astroglia, and blocked by beta1 integrin neutralizing antisera and the tyrosine kinase antagonist genistein. Increases depended upon extracellular calcium and intracellular store release. Ligand-induced effects were reduced by voltage-sensitive calcium channel and NMDA receptor antagonists, but blocked by tetrodotoxin or AMPA receptor antagonists. These results indicate that integrin ligation triggers AMPA receptor/depolarization-dependent calcium influx followed by intracellular store release and suggest the possibility that integrin modulation of activity-induced changes in [Ca(2+)]i contributes importantly to lasting synaptic plasticity in forebrain neurons.
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Affiliation(s)
- C-Y Lin
- Department of Anatomy and Neurobiology, University of California, Irvine CA 92697-4292, USA
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18
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Kam AYF, Tse TTM, Kwan DHT, Wong YH. Formyl peptide receptor like 1 differentially requires mitogen-activated protein kinases for the induction of glial fibrillary acidic protein and interleukin-1α in human U87 astrocytoma cells. Cell Signal 2007; 19:2106-17. [PMID: 17643960 DOI: 10.1016/j.cellsig.2007.06.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Revised: 06/08/2007] [Accepted: 06/12/2007] [Indexed: 11/21/2022]
Abstract
Mitogen-activated protein kinases (MAPKs) are not only pivotal mediators of signal transduction but they also regulate diverse biological processes ranging from survival, proliferation and differentiation to apoptosis. By using human U87 astrocytoma and transfected FPRL1/CHO cells, we have demonstrated that activation of FPRL1 with WKYMVM effectively phosphorylated JNK and ERK. Interestingly, p38 MAPK activation was only seen with FPRL1/CHO cells. The MAPK phosphorylations in response to WKYMVM were blocked by WRW(4) (a selective FPRL1 antagonist), but not cyclosporine H (a well-known FPR antagonist). The key signaling intermediates in the MAPK pathways were also delineated. G(i)/G(o) proteins, Src family tyrosine kinases, but not phosphatidylinositol-3 kinase, protein kinase C and calmodulin-dependent kinase II, were required to transmit signals from FPRL1 toward JNK, ERK and p38 MAPK. Furthermore, phospholipase Cbeta was distinctively involved in the regulation of JNK but not the other MAPKs. Importantly, WKYMVM-stimulated U87 cells triggered noticeable increases in glial fibrillary acidic protein (GFAP) and interleukin-1alpha (IL-1alpha), which are correlated with reactive astrocytosis. In contrast, GFAP expression was not altered following stimulation with N-formyl-methionyl-leucyl-phenylalanine. Moreover, inhibitions of G(i)/G(o) proteins and JNK completely abolished both GFAP and IL-1alpha upregulations by FPRL1, while blockade of the MEK/ERK cascade exclusively suppressed the GFAP production. Consistently, overexpression of MEK1 and constitutively active JNKK in U87 cells led to ERK and JNK activation, respectively, which was accompanied with markedly increased GFAP production. We have thus identified a possible linkage among FPRL1, MAPKs, astrocytic activation and the inflammatory response.
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Affiliation(s)
- Angel Y F Kam
- Department of Biochemistry, Molecular Neuroscience Center and Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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19
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Ksiazek I, Burkhardt C, Lin S, Seddik R, Maj M, Bezakova G, Jucker M, Arber S, Caroni P, Sanes JR, Bettler B, Ruegg MA. Synapse loss in cortex of agrin-deficient mice after genetic rescue of perinatal death. J Neurosci 2007; 27:7183-95. [PMID: 17611272 PMCID: PMC6794585 DOI: 10.1523/jneurosci.1609-07.2007] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Agrin-deficient mice die at birth because of aberrant development of the neuromuscular junctions. Here, we examined the role of agrin at brain synapses. We show that agrin is associated with excitatory but not inhibitory synapses in the cerebral cortex. Most importantly, we examined the brains of agrin-deficient mice whose perinatal death was prevented by the selective expression of agrin in motor neurons. We find that the number of presynaptic and postsynaptic specializations is strongly reduced in the cortex of 5- to 7-week-old mice. Consistent with a reduction in the number of synapses, the frequency of miniature postsynaptic currents was greatly decreased. In accordance with the synaptic localization of agrin to excitatory synapses, changes in the frequency were only detected for excitatory but not inhibitory synapses. Moreover, we find that the muscle-specific receptor tyrosine kinase MuSK, which is known to be an essential component of agrin-induced signaling at the neuromuscular junction, is also localized to a subset of excitatory synapses. Finally, some components of the mitogen-activated protein (MAP) kinase pathway, which has been shown to be activated by agrin in cultured neurons, are deregulated in agrin-deficient mice. In summary, our results provide strong evidence that agrin plays an important role in the formation and/or the maintenance of excitatory synapses in the brain, and we provide evidence that this function involves MAP kinase signaling.
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Affiliation(s)
| | | | | | - Riad Seddik
- Institute of Physiology, Department of Clinical-Biological Sciences, University of Basel, CH-4056 Basel, Switzerland
| | | | | | - Mathias Jucker
- Department of Cellular Neurology, Hertie-Institute of Clinical Brain Research, D-72076 Tübingen, Germany
| | - Silvia Arber
- Biozentrum and
- Friedrich Miescher Institute, CH-4058 Basel, Switzerland, and
| | - Pico Caroni
- Friedrich Miescher Institute, CH-4058 Basel, Switzerland, and
| | - Joshua R. Sanes
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 01238
| | - Bernhard Bettler
- Institute of Physiology, Department of Clinical-Biological Sciences, University of Basel, CH-4056 Basel, Switzerland
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20
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Tournell CE, Bergstrom RA, Ferreira A. Progesterone-induced agrin expression in astrocytes modulates glia-neuron interactions leading to synapse formation. Neuroscience 2006; 141:1327-38. [PMID: 16777347 DOI: 10.1016/j.neuroscience.2006.05.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Revised: 04/24/2006] [Accepted: 05/04/2006] [Indexed: 11/20/2022]
Abstract
Experimental evidence recently obtained suggests that synaptogenesis is a tripartite event in which not only pre- and post-synaptic neurons but also glial cells play a key role. However, the molecular mechanisms by which glia modulate the formation of synapses in the CNS remain poorly understood. In the present study, we analyzed the role of astrocytes in synapse formation in cultured hippocampal rat neurons. For these experiments, hippocampal neurons were cultured in the presence or absence of a monolayer of astrocytes. Our results indicated that hippocampal neurons cultured in the presence of astrocytes formed more synapses than the ones cultured in their absence only when kept in N2 serum-free medium. To get insights into the potential molecular mechanisms underlying this effect, we analyzed the expression of proteins known to induce synapse formation in hippocampal neurons. A significant increase in agrin expression was detected in astrocytes cultured in N2 serum-free medium when compared with the ones cultured in serum containing medium. Experiments performed using different components of the N2 mixture indicated that progesterone induced the expression of agrin in astrocytes. Taken collectively, these results provide evidence supporting a role for astrocytes in synapse formation in central neurons. Furthermore, they identified agrin as a potential mediator of this effect, and astrocytes as a bridge between the endocrine and nervous systems during synaptogenesis.
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Affiliation(s)
- C E Tournell
- Department of Cell and Molecular Biology, The Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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21
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Hilgenberg LGW, Su H, Gu H, O'Dowd DK, Smith MA. Alpha3Na+/K+-ATPase is a neuronal receptor for agrin. Cell 2006; 125:359-69. [PMID: 16630822 DOI: 10.1016/j.cell.2006.01.052] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Revised: 12/12/2005] [Accepted: 01/18/2006] [Indexed: 11/25/2022]
Abstract
Agrin, through its interaction with the receptor tyrosine kinase MuSK, mediates accumulation of acetylcholine receptors (AChR) at the developing neuromuscular junction. Agrin has also been implicated in several functions in brain. However, the mechanism by which agrin exerts its effects in neural tissue is unknown. Here we present biochemical evidence that agrin binds to the alpha3 subunit of the Na+/K+-ATPase (NKA) in CNS neurons. Colocalization with agrin binding sites at synapses supports the hypothesis that the alpha3NKA is a neuronal agrin receptor. Agrin inhibition of alpha3NKA activity results in membrane depolarization and increased action potential frequency in cortical neurons in culture and acute slice. An agrin fragment that acts as a competitive antagonist depresses action potential frequency, showing that endogenous agrin regulates native alpha3NKA function. These data demonstrate that, through its interaction with the alpha3NKA, agrin regulates activity-dependent processes in neurons, providing a molecular framework for agrin action in the CNS.
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Affiliation(s)
- Lutz G W Hilgenberg
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA 92697, USA
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22
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Dityatev A, Frischknecht R, Seidenbecher CI. Extracellular matrix and synaptic functions. Results Probl Cell Differ 2006; 43:69-97. [PMID: 17068968 DOI: 10.1007/400_025] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Comprehensive analysis of neuromuscular junction formation and recent data on synaptogenesis and long-term potentiation in the central nervous system revealed a number of extracellular matrix (ECM) molecules regulating different aspects of synaptic differentiation and function. The emerging mechanisms comprise interactions of ECM components with their cell surface receptors coupled to tyrosine kinase activities (agrin, integrin ligands, and reelin) and interactions with ion channels and transmitter receptors (Narp, tenascin-R and tenascin-C). These interactions may shape synaptic transmission and plasticity of excitatory synapses either via regulation of Ca2+ entry and postsynaptic expression of transmitter receptors or via control of GABAergic inhibition. The ECM molecules, derived from both neurons and glial cells and secreted into the extracellular space in an activity-dependent manner, may also shape synaptic plasticity through setting diffusion constraints for neurotransmitters, trophic factors and ions.
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Affiliation(s)
- Alexander Dityatev
- Institut für Neurophysiologie und Pathophysiologie, Universitätsklinikum Hamburg-Eppendorf, Germany.
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23
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Kumar P, Ferns MJ, Meizel S. Identification of agrinSN isoform and muscle-specific receptor tyrosine kinase in sperm. Biochem Biophys Res Commun 2006; 342:522-8. [PMID: 16487930 DOI: 10.1016/j.bbrc.2006.01.161] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Accepted: 01/28/2006] [Indexed: 10/25/2022]
Abstract
We previously demonstrated several nicotinic acetylcholine receptor (nAChR) subunits and associated proteins in human sperm. Here, we identified in sperm for the first time two additional nAChR-associated molecules: (1) agrin(SN)Z(+) in human sperm localized in the posterior post-acrosomal, neck, and flagellar mid-piece regions; (2) a low-molecular weight isoform of muscle-specific receptor tyrosine kinase in human and mouse sperm localized in the flagellar mid-piece of human sperm.
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Affiliation(s)
- Priyadarsini Kumar
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, CA 95616, USA.
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