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Prömer J, Barresi C, Herbst R. From phosphorylation to phenotype - Recent key findings on kinase regulation, downstream signaling and disease surrounding the receptor tyrosine kinase MuSK. Cell Signal 2023; 104:110584. [PMID: 36608736 DOI: 10.1016/j.cellsig.2022.110584] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 12/16/2022] [Accepted: 12/31/2022] [Indexed: 01/04/2023]
Abstract
Muscle-specific kinase (MuSK) is the key regulator of neuromuscular junction development. MuSK acts via several distinct pathways and is responsible for pre- and postsynaptic differentiation. MuSK is unique among receptor tyrosine kinases as activation and signaling are particularly tightly regulated. Initiation of kinase activity requires Agrin, a heparan sulphate proteoglycan derived from motor neurons, the low-density lipoprotein receptor-related protein-4 (Lrp4) and the intracellular adaptor protein Dok-7. There is a great knowledge gap between MuSK activation and downstream signaling. Recent studies using omics techniques have addressed this knowledge gap, thereby greatly contributing to a better understanding of MuSK signaling. Impaired MuSK signaling causes severe muscle weakness as described in congenital myasthenic syndromes or myasthenia gravis but the underlying pathophysiology is often unclear. This review focuses on recent advances in deciphering MuSK activation and downstream signaling. We further highlight latest break-throughs in understanding and treatment of MuSK-related disorders and discuss the role of MuSK in non-muscle tissue.
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Affiliation(s)
- Jakob Prömer
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
| | - Cinzia Barresi
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
| | - Ruth Herbst
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.
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2
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Herbst R. MuSk function during health and disease. Neurosci Lett 2019; 716:134676. [PMID: 31811897 DOI: 10.1016/j.neulet.2019.134676] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 12/02/2019] [Accepted: 12/04/2019] [Indexed: 02/06/2023]
Abstract
The receptor tyrosine kinase MuSK (muscle-specific kinase) is the key signaling molecule during the formation of a mature and functional neuromuscular junction (NMJ). Signal transduction events downstream of MuSK activation induce both pre- and postsynaptic differentiation, which, most prominently, includes the clustering of acetylcholine receptors (AChRs) at synaptic sites. MuSK activation requires a complex interplay between its co-receptor Lrp4 (low-density lipoprotein receptor-related protein-4), the motor neuron-derived heparan-sulfate proteoglycan Agrin and the intracellular adaptor protein Dok-7. A tight regulation of MuSK kinase activity is crucial for proper NMJ development. Defects in MuSK signaling are the cause of muscle weakness as reported in congenital myasthenic syndromes and myasthenia gravis. This review focuses on recent structure-based analyses of MuSK, Agrin, Lrp4 and Dok-7 interactions and their function during MuSK activation. Conclusions about the regulation of the MuSK kinase that were derived from molecular structures will be highlighted. In addition, the role of MuSK during development and disease will be discussed.
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Affiliation(s)
- Ruth Herbst
- Medical University of Vienna, Center for Pathophysiology, Infectiology and Immunology, Kinderspitalgasse 15, 1090 Vienna, Austria.
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3
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Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture. Cells 2019; 8:cells8070671. [PMID: 31269763 PMCID: PMC6678492 DOI: 10.3390/cells8070671] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ). Autoantibodies target key molecules at the NMJ, such as the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (Lrp4), that lead by a range of different pathogenic mechanisms to altered tissue architecture and reduced densities or functionality of AChRs, reduced neuromuscular transmission, and therefore a severe fatigable skeletal muscle weakness. In this review, we give an overview of the history and clinical aspects of MG, with a focus on the structure and function of myasthenic autoantigens at the NMJ and how they are affected by the autoantibodies' pathogenic mechanisms. Furthermore, we give a short overview of the cells that are implicated in the production of the autoantibodies and briefly discuss diagnostic challenges and treatment strategies.
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4
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Cognitive dysfunction in mice with passively induced MuSK antibody seropositive myasthenia gravis. J Neurol Sci 2019; 399:15-21. [DOI: 10.1016/j.jns.2019.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 01/23/2019] [Accepted: 02/01/2019] [Indexed: 11/19/2022]
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5
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Fundamental Molecules and Mechanisms for Forming and Maintaining Neuromuscular Synapses. Int J Mol Sci 2018; 19:ijms19020490. [PMID: 29415504 PMCID: PMC5855712 DOI: 10.3390/ijms19020490] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 01/24/2018] [Accepted: 01/29/2018] [Indexed: 02/08/2023] Open
Abstract
The neuromuscular synapse is a relatively large synapse with hundreds of active zones in presynaptic motor nerve terminals and more than ten million acetylcholine receptors (AChRs) in the postsynaptic membrane. The enrichment of proteins in presynaptic and postsynaptic membranes ensures a rapid, robust, and reliable synaptic transmission. Over fifty years ago, classic studies of the neuromuscular synapse led to a comprehensive understanding of how a synapse looks and works, but these landmark studies did not reveal the molecular mechanisms responsible for building and maintaining a synapse. During the past two-dozen years, the critical molecular players, responsible for assembling the specialized postsynaptic membrane and regulating nerve terminal differentiation, have begun to be identified and their mechanism of action better understood. Here, we describe and discuss five of these key molecular players, paying heed to their discovery as well as describing their currently understood mechanisms of action. In addition, we discuss the important gaps that remain to better understand how these proteins act to control synaptic differentiation and maintenance.
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Karvonen H, Summala K, Niininen W, Barker HR, Ungureanu D. Interaction between ROR1 and MuSK activation complex in myogenic cells. FEBS Lett 2018; 592:434-445. [DOI: 10.1002/1873-3468.12966] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 12/21/2017] [Accepted: 12/22/2017] [Indexed: 12/14/2022]
Affiliation(s)
- Hanna Karvonen
- BioMediTech Institute; University of Tampere; Finland
- Faculty of Medicine and Life Sciences; University of Tampere; Finland
| | - Katja Summala
- Department of Biological and Environmental Science; University of Jyväskylä; Finland
| | - Wilhelmiina Niininen
- BioMediTech Institute; University of Tampere; Finland
- Faculty of Medicine and Life Sciences; University of Tampere; Finland
| | - Harlan R. Barker
- Faculty of Medicine and Life Sciences; University of Tampere; Finland
| | - Daniela Ungureanu
- BioMediTech Institute; University of Tampere; Finland
- Faculty of Medicine and Life Sciences; University of Tampere; Finland
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7
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Remédio L, Gribble KD, Lee JK, Kim N, Hallock PT, Delestrée N, Mentis GZ, Froemke RC, Granato M, Burden SJ. Diverging roles for Lrp4 and Wnt signaling in neuromuscular synapse development during evolution. Genes Dev 2017; 30:1058-69. [PMID: 27151977 PMCID: PMC4863737 DOI: 10.1101/gad.279745.116] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 03/31/2016] [Indexed: 11/25/2022]
Abstract
In this study, Remédio et al. use mice and zebrafish to show that muscle prepatterning in mammals and zebrafish is established by different mechanisms. Their findings demonstrate that Agrin/Lrp4/MuSK signaling plays an essential role in neuromuscular synapse formation in both fish and mammals, whereas Wnt signaling is dispensable. Motor axons approach muscles that are prepatterned in the prospective synaptic region. In mice, prepatterning of acetylcholine receptors requires Lrp4, a LDLR family member, and MuSK, a receptor tyrosine kinase. Lrp4 can bind and stimulate MuSK, strongly suggesting that association between Lrp4 and MuSK, independent of additional ligands, initiates prepatterning in mice. In zebrafish, Wnts, which bind the Frizzled (Fz)-like domain in MuSK, are required for prepatterning, suggesting that Wnts may contribute to prepatterning and neuromuscular development in mammals. We show that prepatterning in mice requires Lrp4 but not the MuSK Fz-like domain. In contrast, prepatterning in zebrafish requires the MuSK Fz-like domain but not Lrp4. Despite these differences, neuromuscular synapse formation in zebrafish and mice share similar mechanisms, requiring Lrp4, MuSK, and neuronal Agrin but not the MuSK Fz-like domain or Wnt production from muscle. Our findings demonstrate that evolutionary divergent mechanisms establish muscle prepatterning in zebrafish and mice.
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Affiliation(s)
- Leonor Remédio
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, New York 10016, USA
| | - Katherine D Gribble
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Jennifer K Lee
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, New York 10016, USA
| | - Natalie Kim
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, New York 10016, USA
| | - Peter T Hallock
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, New York 10016, USA
| | - Nicolas Delestrée
- Center for Motor Neuron Biology and Disease, Columbia University, New York, New York 10032, USA; Department of Pathology and Cell Biology, Columbia University, New York, New York 10032, USA; Department of Neurology, Columbia University, New York, New York 10032, USA
| | - George Z Mentis
- Center for Motor Neuron Biology and Disease, Columbia University, New York, New York 10032, USA; Department of Pathology and Cell Biology, Columbia University, New York, New York 10032, USA; Department of Neurology, Columbia University, New York, New York 10032, USA
| | - Robert C Froemke
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, New York 10016, USA
| | - Michael Granato
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Steven J Burden
- Molecular Neurobiology Program, Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, New York 10016, USA
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Coronin 6 regulates acetylcholine receptor clustering through modulating receptor anchorage to actin cytoskeleton. J Neurosci 2014; 34:2413-21. [PMID: 24523531 DOI: 10.1523/jneurosci.3226-13.2014] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The maintenance of a high density of neurotransmitter receptors at the postsynaptic apparatus is critical for efficient neurotransmission. Acetylcholine receptors (AChRs) are neurotransmitter receptors densely packed on the postsynaptic muscle membrane at the neuromuscular junction (NMJ) via anchoring onto the actin cytoskeletal network. However, how the receptor-associated actin is coordinately regulated is not fully understood. We report here that Coronin 6, a newly identified member of the coronin family, is highly enriched at adult NMJs and regulates AChR clustering through modulating the interaction between receptors and the actin cytoskeletal network. Experiments with cultured myotubes reveal that Coronin 6 is important for both agrin- and laminin-induced AChR clustering. Furthermore, Coronin 6 forms a complex with AChRs and actin in a manner dependent on its C-terminal region and a conserved Arg(29) residue at the N terminus, both of which are critical for the cytoskeletal anchorage of AChRs. Importantly, in vivo knockdown of Coronin 6 in mouse skeletal muscle fibers leads to destabilization of AChR clusters. Together, these findings demonstrate that Coronin 6 is a critical regulator of AChR clustering at the postsynaptic region of the NMJs through modulating the receptor-anchored actin cytoskeleton.
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Abstract
Muscle-specific kinase (MuSK) is essential for each step in neuromuscular synapse formation. Before innervation, MuSK initiates postsynaptic differentiation, priming the muscle for synapse formation. Approaching motor axons recognize the primed, or prepatterned, region of muscle, causing motor axons to stop growing and differentiate into specialized nerve terminals. MuSK controls presynaptic differentiation by causing the clustering of Lrp4, which functions as a direct retrograde signal for presynaptic differentiation. Developing synapses are stabilized by neuronal Agrin, which is released by motor nerve terminals and binds to Lrp4, a member of the low-density lipoprotein receptor family, stimulating further association between Lrp4 and MuSK and increasing MuSK kinase activity. In addition, MuSK phosphorylation is stimulated by an inside-out ligand, docking protein-7 (Dok-7), which is recruited to tyrosine-phosphorylated MuSK and increases MuSK kinase activity. Mutations in MuSK and in genes that function in the MuSK signaling pathway, including Dok-7, cause congenital myasthenia, and autoantibodies to MuSK, Lrp4, and acetylcholine receptors are responsible for myasthenia gravis.
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Barik A, Xiong WC, Mei L. MuSK: A Kinase Critical for the Formation and Maintenance of the Neuromuscular Junction. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/978-1-61779-824-5_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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11
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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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12
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Osman AA, Schrader AD, Hawkes AJ, Akil O, Bergeron A, Lustig LR, Simmons DD. Muscle-like nicotinic receptor accessory molecules in sensory hair cells of the inner ear. Mol Cell Neurosci 2008; 38:153-69. [PMID: 18420419 PMCID: PMC2480618 DOI: 10.1016/j.mcn.2008.02.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Revised: 01/28/2008] [Accepted: 02/12/2008] [Indexed: 11/30/2022] Open
Abstract
Nothing is known about the regulation of nicotinic acetylcholine receptors (nAChRs) in hair cells of the inner ear. MuSK, rapsyn and RIC-3 are accessory molecules associated with muscle and brain nAChR function. We demonstrate that these accessory molecules are expressed in the inner ear raising the possibility of a muscle-like mechanism for clustering and assembly of nAChRs in hair cells. We focused our investigations on rapsyn and RIC-3. Rapsyn interacts with the cytoplasmic loop of nAChR alpha9 subunits but not nAChR alpha10 subunits. Although rapsyn and RIC-3 increase nAChR alpha9 expression, rapsyn plays a greater role in receptor clustering while RIC-3 is important for acetylcholine-induced calcium responses. Our data suggest that RIC-3 facilitates receptor function, while rapsyn enhances receptor clustering at the cell surface.
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MESH Headings
- Animals
- Bungarotoxins/pharmacology
- Calcium/metabolism
- Female
- Hair Cells, Auditory, Inner/cytology
- Hair Cells, Auditory, Inner/metabolism
- Humans
- Intracellular Signaling Peptides and Proteins/genetics
- Intracellular Signaling Peptides and Proteins/metabolism
- Kidney/cytology
- LLC-PK1 Cells
- Male
- Mice
- Mice, Inbred C57BL
- Muscle Proteins/metabolism
- Pregnancy
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor Protein-Tyrosine Kinases/genetics
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/metabolism
- Receptors, Nicotinic/genetics
- Receptors, Nicotinic/metabolism
- Swine
- Synapses/metabolism
- Transfection
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Affiliation(s)
- Abdullah A. Osman
- Department of Otolaryngology, Washington University School of Medicine, 660 South Euclid Ave., St. Louis MO 63110
| | - Angela D. Schrader
- Department of Otolaryngology, Washington University School of Medicine, 660 South Euclid Ave., St. Louis MO 63110
| | - Aubrey J. Hawkes
- Department of Otolaryngology, Washington University School of Medicine, 660 South Euclid Ave., St. Louis MO 63110
- Department of Physiolgical Science, University of California, Los Angeles
| | - Omar Akil
- Department of Otolaryngology-Head & Neck Surgery, University of California San Francisco, 400 Parnassus Avenue, San Francisco CA 94143
| | - Adam Bergeron
- Program in Neuroscience, Washington University School of Medicine, 660 South Euclid Ave., St. Louis MO 63110
| | - Lawrence R. Lustig
- Department of Otolaryngology-Head & Neck Surgery, University of California San Francisco, 400 Parnassus Avenue, San Francisco CA 94143
| | - Dwayne D. Simmons
- Department of Otolaryngology, Washington University School of Medicine, 660 South Euclid Ave., St. Louis MO 63110
- Department of Anatomy and Neurobiology, Washington University School of Medicine, 660 South Euclid Ave., St. Louis MO 63110
- Program in Neuroscience, Washington University School of Medicine, 660 South Euclid Ave., St. Louis MO 63110
- Department of Physiolgical Science, University of California, Los Angeles
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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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14
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Lok KC, Fu AKY, Ip FCF, Wong YH, Ip NY. Expression of G protein β subunits in rat skeletal muscle after nerve injury: Implication in the regulation of neuregulin signaling. Neuroscience 2007; 146:594-603. [PMID: 17368953 DOI: 10.1016/j.neuroscience.2007.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 02/02/2007] [Accepted: 02/03/2007] [Indexed: 11/21/2022]
Abstract
Tight regulation of gene transcription is critical in muscle development as well as during the formation and maintenance of the neuromuscular junction (NMJ). We previously demonstrated that the transcription of G protein beta1 (Gbeta1) is enhanced by treatment of cultured myotubes with neuregulin (NRG), a trophic factor that plays an important role in neural development. In the current study, we report that the transcript levels of Gbeta1 and Gbeta2 subunits in skeletal muscle are up-regulated following sciatic nerve injury or blockade of nerve activity. These observations prompted us to explore the possibility that G protein subunits regulate NRG-mediated signaling and gene transcription. We showed that overexpression of Gbeta1 or Gbeta2 in COS7 cells attenuates NRG-induced extracellular signal-regulated kinase (ERK) 1/2 activation, whereas suppression of Gbeta2 expression in C2C12 myotubes enhances NRG-mediated ERK1/2 activation and c-fos transcription. These results suggest that expression of Gbeta protein negatively regulates NRG-stimulated gene transcription in cultured myotubes. Taken together, our observations provide evidence that specific heterotrimeric G proteins regulate NRG-mediated signaling and gene transcription during rat muscle development.
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Affiliation(s)
- K-C Lok
- Department of Biochemistry, Biotechnology Research Institute and Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay Road, Hong Kong, China
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15
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Lefebvre JL, Jing L, Becaficco S, Franzini-Armstrong C, Granato M. Differential requirement for MuSK and dystroglycan in generating patterns of neuromuscular innervation. Proc Natl Acad Sci U S A 2007; 104:2483-8. [PMID: 17284594 PMCID: PMC1892914 DOI: 10.1073/pnas.0610822104] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Vertebrates display diverse patterns of neuromuscular innervation, but little is known about how such diversity is generated. In mammals, neuromuscular junctions form predominantly at equatorial locations, giving rise to a focal innervation pattern along a central endplate band. In addition, vertebrate striated muscles exhibit two nonfocal neuromuscular patterns, myoseptal and distributed innervation. Although agrin-MuSK-rapsyn signaling is essential for the focal innervation pattern, it is unknown whether the same genetic program also controls synaptogenesis at nonfocal innervation sites. Here we show that one of three transcripts generated by the zebrafish unplugged locus, unplugged FL, encodes the zebrafish MuSK ortholog. We demonstrate that UnpFL/MuSK is critical for the assembly of focal synapses in zebrafish and that it cooperates with dystroglycan in the formation of nonfocal myoseptal and distributed synapses. Our results provide the first genetic evidence that neuromuscular synapse formation can occur in the absence of MuSK and that the combinatorial function of UnpFL/MuSK and dystroglycan generates diverse patterns of vertebrate neuromuscular innervation.
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Affiliation(s)
- Julie L. Lefebvre
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
| | - Lili Jing
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
| | - Sara Becaficco
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
| | - Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
| | - Michael Granato
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
- To whom correspondence should be addressed. E-mail:
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16
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Garcia-Osta A, Tsokas P, Pollonini G, Landau EM, Blitzer R, Alberini CM. MuSK expressed in the brain mediates cholinergic responses, synaptic plasticity, and memory formation. J Neurosci 2006; 26:7919-32. [PMID: 16870737 PMCID: PMC6674217 DOI: 10.1523/jneurosci.1674-06.2006] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Muscle-specific tyrosine kinase receptor (MuSK) has been believed to be mainly expressed and functional in muscle, in which it mediates the formation of neuromuscular junctions. Here we show that MuSK is expressed in the brain, particularly in neurons, as well as in non-neuronal tissues. We also provide evidence that MuSK expression in the hippocampus is required for memory consolidation, because temporally restricted knockdown after training impairs memory retention. Hippocampal disruption of MuSK also prevents the learning-dependent induction of both cAMP response element binding protein (CREB) phosphorylation and CCAAT enhancer binding protein beta (C/EBPbeta) expression, suggesting that the role of MuSK during memory consolidation critically involves the CREB-C/EBP pathway. Furthermore, we found that MuSK also plays an important role in mediating hippocampal oscillatory activity in the theta frequency as well as in the induction and maintenance of long-term potentiation, two synaptic responses that correlate with memory formation. We conclude that MuSK plays an important role in brain functions, including memory formation. Therefore, its expression and role are broader than what was believed previously.
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17
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Cheusova T, Khan MA, Enz R, Hashemolhosseini S. Identification of developmentally regulated expression of MuSK in astrocytes of the rodent retina. J Neurochem 2006; 99:450-7. [PMID: 16899069 DOI: 10.1111/j.1471-4159.2006.04086.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One of the master regulators of postsynaptic neuromuscular synaptogenesis is the muscle-specific receptor tyrosine kinase (MuSK). In mammals prominent MuSK expression is believed to be restricted to skeletal muscle. Upon activation by nerve-derived agrin MuSK-dependent signalling participates in both the induction of genes encoding postsynaptic components and aggregation of nicotinic acetylcholine receptors (AChR) in the subsynaptic muscle membrane. Strikingly, expression of certain isoforms of nerve-derived agrin can also be detected in the CNS. In this study, we examined the expression of MuSK in the brain and eye of rodents. In the retina MuSK was expressed in astrocytes between postnatal days 7 and 14, i.e. at the time when the eyes open. We found that agrin was localized adjacent to MuSK-expressing astrocytes which in turn were detected close to the inner limiting membrane of the rodent retina. In summary, the presence of MuSK on retinal astrocytes suggests a novel role of MuSK signalling pathways in the CNS.
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Affiliation(s)
- Tatiana Cheusova
- Institut für Biochemie, Universität Erlangen-Nürnberg, Erlangen, Germany
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Shigemoto K, Kubo S, Maruyama N, Hato N, Yamada H, Jie C, Kobayashi N, Mominoki K, Abe Y, Ueda N, Matsuda S. Induction of myasthenia by immunization against muscle-specific kinase. J Clin Invest 2006; 116:1016-24. [PMID: 16557298 PMCID: PMC1409737 DOI: 10.1172/jci21545] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 02/07/2006] [Indexed: 11/17/2022] Open
Abstract
Muscle-specific kinase (MuSK) is critical for the synaptic clustering of nicotinic acetylcholine receptors (AChRs) and plays multiple roles in the organization and maintenance of neuromuscular junctions (NMJs). MuSK is activated by agrin, which is released from motoneurons, and induces AChR clustering at the postsynaptic membrane. Although autoantibodies against the ectodomain of MuSK have been found in a proportion of patients with generalized myasthenia gravis (MG), it is unclear whether MuSK autoantibodies are the causative agent of generalized MG. In the present study, rabbits immunized with MuSK ectodomain protein manifested MG-like muscle weakness with a reduction of AChR clustering at the NMJs. The autoantibodies activated MuSK and blocked AChR clustering induced by agrin or by mediators that do not activate MuSK. Thus MuSK autoantibodies rigorously inhibit AChR clustering mediated by multiple pathways, an outcome that broadens our general comprehension of the pathogenesis of MG.
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Affiliation(s)
- Kazuhiro Shigemoto
- Department of Preventive Medicine, Ehime University School of Medicine, Ehime, Japan.
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19
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Fu AKY, Ip FCF, Fu WY, Cheung J, Wang JH, Yung WH, Ip NY. Aberrant motor axon projection, acetylcholine receptor clustering, and neurotransmission in cyclin-dependent kinase 5 null mice. Proc Natl Acad Sci U S A 2005; 102:15224-9. [PMID: 16203963 PMCID: PMC1257743 DOI: 10.1073/pnas.0507678102] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cyclin-dependent kinase (Cdk)5 is a key regulator of neural development. We have previously demonstrated that Cdk5/p35 are localized to the postsynaptic muscle and are implicated in the regulation of neuregulin/ErbB signaling in myotube culture. To further elucidate whether Cdk5 activity contributes to neuromuscular junction (NMJ) development in vivo, the NMJ of Cdk5-/- mice was examined. Consistent with our previous demonstration that Cdk5 phosphorylates ErbB2/3 to regulate its tyrosine phosphorylation, we report here that the phosphorylation of ErbB2 and ErbB3 and the ErbB2 kinase activity are reduced in Cdk5-deficient muscle. In addition, Cdk5-/- mice also display morphological abnormalities at the NMJ pre- and postsynaptically. Whereas the outgrowth of the main nerve trunk is grossly normal, the intramuscular nerve projections exhibit profuse and anomalous branching patterns in the Cdk5-/- embryos. The central band of acetylcholine receptor (AChR) clusters is also wider in Cdk5-/- diaphragms, together with the absence of S100 immunoreactivity along the phrenic nerve during late embryonic stages. Moreover, we unexpectedly discovered that the agrin-induced formation of large AChR clusters is significantly increased in primary muscle cultures prepared from Cdk5-null mice and in C2C12 myotubes when Cdk5 activity was suppressed. These abnormalities are accompanied by elevated frequency of miniature endplate potentials in Cdk5-null diaphragm. Taken together, our findings reveal the essential role of Cdk5 in regulating the development of motor axons and neuromuscular synapses in vivo.
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Affiliation(s)
- Amy K Y Fu
- Department of Biochemistry, Biotechnology Research Institute, and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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Xu X, Fu AKY, Ip FCF, Wu CP, Duan S, Poo MM, Yuan XB, Ip NY. Agrin regulates growth cone turning of Xenopus spinal motoneurons. Development 2005; 132:4309-16. [PMID: 16141222 DOI: 10.1242/dev.02016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The pivotal role of agrin in inducing postsynaptic specializations at neuromuscular junctions has been well characterized. Increasing evidence suggests that agrin is also involved in neuronal development. In this study,we found that agrin inhibited neurite extension and, more importantly, a gradient of agrin induced repulsive growth-cone turning in cultured Xenopus spinal neurons. Incubation with a neutralizing antibody to agrin or expression of the extracellular domain of muscle-specific kinase, a component of the agrin receptor complex, abolished these effects of agrin. Agrin-induced repulsive growth-cone turning requires the activity of PI3-kinase and Ca2+ signaling. In addition, the expression of dominant-negative Rac1 inhibited neurite extension and blocked agrin-mediated growth-cone turning. Taken together, our findings suggest that agrin regulates neurite extension and provide evidence for an unanticipated role of agrin in growth-cone steering in developing neurons.
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Affiliation(s)
- Xiaohua Xu
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai 200031, China
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21
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Affiliation(s)
- Kwok-On Lai
- Department of Biochemistry, Molecular Neuroscience Center and Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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22
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Sharma SK, Wallace BG. Lithium inhibits a late step in agrin-induced AChR aggregation. JOURNAL OF NEUROBIOLOGY 2003; 54:346-57. [PMID: 12500310 DOI: 10.1002/neu.10134] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Agrin activates an intracellular signaling pathway to induce the formation of postsynaptic specializations on muscle fibers. In myotubes in culture, this pathway has been shown to include autophosphorylation of the muscle-specific kinase MuSK, activation of Src-family kinases, tyrosine phosphorylation of the acetylcholine receptor (AChR) beta subunit, a decrease in receptor detergent extractability, and the accumulation of AChRs into high-density aggregates. Here we report that treating chick myotubes with lithium prevented any detectable agrin-induced change in AChR distribution without affecting the number of AChRs or the agrin-induced change in AChR tyrosine phosphorylation and detergent extractability. Lithium treatment also increased the rate at which AChR aggregates disappeared when agrin was removed. The effects of lithium developed slowly over the course of approximately 12 h. Thus, sensitivity to lithium identifies a late step in the agrin signaling pathway, after agrin-induced MuSK and AChR phosphorylation, that is necessary for the recruitment of AChRs into visible aggregates.
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Affiliation(s)
- S K Sharma
- Department of Physiology and Biophysics, C240, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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23
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Watty A, Burden SJ. MuSK glycosylation restrains MuSK activation and acetylcholine receptor clustering. J Biol Chem 2002; 277:50457-62. [PMID: 12399462 DOI: 10.1074/jbc.m208664200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MuSK, a muscle-specific receptor tyrosine kinase that is activated by agrin, has a critical role in neuromuscular synapse formation. In cultured myotubes, agrin stimulates the rapid phosphorylation of MuSK, leading to MuSK activation and tyrosine phosphorylation and clustering of acetylcholine receptors. Agrin, however, fails to stimulate tyrosine phosphorylation of MuSK that is force-expressed in myoblasts and fibroblasts, indicating that myotubes contain an additional activity that is required for agrin to stimulate MuSK. Certain glycosyltransferases are expressed selectively at synaptic sites in skeletal muscle, raising the possibility that carbohydrate modifications of MuSK, catalyzed by glycosyltransferases expressed selectively in myotubes, may be essential for agrin to bind and activate MuSK. We identifed two N-linked glycosylation sites in MuSK, and we expressed MuSK mutants lacking one or both N-linked sites into MuSK mutant myotubes to determine whether N-linked carbohydrate modifications of MuSK have a role in MuSK activation. We found that N-linked glycosylation restrains ligand-independent tyrosine phosphorylation of MuSK and downstream signaling but is not necessary for agrin to stimulate MuSK.
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Affiliation(s)
- Anke Watty
- Molecular Neurobiology Program, Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, New York 10016, USA
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24
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Affiliation(s)
- Steven J Burden
- Molecular Neurobiology Program, Skirball Institute, NYU Medical School, 540 First Avenue, New York City, New York 10016, USA.
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25
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Herbst R, Avetisova E, Burden SJ. Restoration of synapse formation in Musk mutant mice expressing a Musk/Trk chimeric receptor. Development 2002; 129:5449-60. [PMID: 12403715 DOI: 10.1242/dev.00112] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mice lacking Musk, a muscle-specific receptor tyrosine kinase that is activated by agrin, fail to form neuromuscular synapses and consequently die at birth because of their failure to move or breathe. We produced mice that express a chimeric receptor, containing the juxtamembrane region of Musk and the kinase domain of TrkA, selectively in muscle, and we crossed this transgene into Musk mutant mice. Expression of this chimeric receptor restores presynaptic and postsynaptic differentiation, including the formation of nerve terminal arbors, synapse-specific transcription, and clustering of postsynaptic proteins, allowing Musk mutant mice to move, breathe and survive as adults. These results show that the juxtamembrane region of Musk, including a single phosphotyrosine docking site, even in the context of a different kinase domain, is sufficient to activate the multiple pathways leading to presynaptic and postsynaptic differentiation in vivo. In addition, we find that Musk protein can be clustered at synaptic sites, even if Musk mRNA is expressed uniformly in muscle. Moreover, acetylcholine receptor clustering and motor terminal branching are restored in parallel, indicating that the extent of presynaptic differentiation is matched to the extent of postsynaptic differentiation.
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Affiliation(s)
- Ruth Herbst
- Molecular Neurobiology Program, Skirball Institute, NYU Medical School, NY 10016, USA.
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26
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Fu AK, Cheung J, Smith FD, Ip FC, Ip NY. Overexpression of muscle specific kinase increases the transcription and aggregation of acetylcholine receptors in Xenopus embryos. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2001; 96:21-9. [PMID: 11731005 DOI: 10.1016/s0169-328x(01)00253-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Muscle specific kinase (MuSK) mediates agrin-induced acetylcholine receptor (AChR) aggregation on muscle membrane at the neuromuscular junction (NMJ). To examine whether MuSK enhances NMJ formation during embryonic development in vivo, the level of expression of MuSK was manipulated in Xenopus embryos and the functional consequence at the NMJ was assessed. We found that overexpression of MuSK enhanced the formation of NMJ by increasing the aggregation of AChRs at innervated regions in developing embryos. The area of AChR aggregation increased by approximately 2-fold in MuSK injected embryos during the critical stages of NMJ formation. Interestingly, overexpression of MuSK in Xenopus embryos was found to induce the level of AChR transcript. Deletion of the Kringle domain in the MuSK construct did not attenuate the observed induction of AChR transcription and aggregation. Taken together, our findings provide the first demonstration that increased level of MuSK expression in vivo significantly elevate the aggregation and transcription of AChR at the NMJ in developing Xenopus embryos.
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Affiliation(s)
- A K Fu
- Department of Biochemistry, Molecular Neuroscience Center and Biotechnology Research Institute, Hong Kong University of Science and Technology, Hong Kong, Clear Water Bay, China
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27
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Ozhogina OA, Trexler M, Bányai L, Llinás M, Patthy L. Origin of fibronectin type II (FN2) modules: structural analyses of distantly-related members of the kringle family idey the kringle domain of neurotrypsin as a potential link between FN2 domains and kringles. Protein Sci 2001; 10:2114-22. [PMID: 11567102 PMCID: PMC2374232 DOI: 10.1110/ps.15801] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Analysis of complete genome sequences has made it clear that fibronectin type II (FN2) modules are present only in the vertebrate lineage, raising intriguing questions about the origin of this module type. Kringle domains display many similarities to FN2 domains; therefore it was suggested previously that they are highly divergent descendants of the same ancestral protein-fold. Since kringles are present in arthropodes, nematodes, and invertebrate chordates as well as in vertebrates, it is suggested that the FN2 domain arose in the vertebrate lineage through major structural modification of the more ancestral kringle fold. To explore this structural transition, in the present work we compare key structural features of two highly divergent kringle domains (the kringle of Caenorhabditis elegans Ror receptor tyrosine kinase and the kringle of rat neurotrypsin) with those of plasminogen kringles and FN2 domains. Our NMR conformation fingerprinting analysis indicates that characteristic (1)H-NMR markers of kringle or FN2 native folding, such as the dispersion of Trp aromatic connectivities and shifts of the Leu(46)/Thr(16) methyl signals, both decrease in the order kringles > neurotrypsin kringle > FN2 domains. These results suggest that the neurotrypsin kringle may represent an intermediate form between typical kringles and FN2 domains.
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Affiliation(s)
- O A Ozhogina
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
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Fu AK, Fu WY, Cheung J, Tsim KW, Ip FC, Wang JH, Ip NY. Cdk5 is involved in neuregulin-induced AChR expression at the neuromuscular junction. Nat Neurosci 2001; 4:374-81. [PMID: 11276227 DOI: 10.1038/86019] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Here we describe an important involvement of Cdk5/p35 in regulating the gene expression of acetylcholine receptor (AChR) at the neuromuscular synapse. Cdk5 and p35 were prominently expressed in embryonic muscle, and concentrated at the neuromuscular junction in adulthood. Neuregulin increased the p35-associated Cdk5 kinase activity in the membrane fraction of cultured C2C12 myotubes. Co-immunoprecipitation studies revealed the association between Cdk5, p35 and ErbB receptors in muscle and cultured myotubes. Inhibition of Cdk5 activity not only blocked the NRG-induced AChR transcription, but also attenuated ErbB activation in cultured myotubes. In light of our finding that overexpression of p35 alone led to an increase in AChR promoter activity in muscle, Cdk5 activation is sufficient to mediate the up-regulation of AChR gene expression. Taken together, these results reveal the unexpected involvement of Cdk5/p35 in neuregulin signaling at the neuromuscular synapse.
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Affiliation(s)
- A K Fu
- Department of Biochemistry, Biotechnology Research Institute, Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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29
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Nakamura T, Aoki S, Kitajima K, Takahashi T, Matsumoto K, Nakamura T. Molecular cloning and characterization of Kremen, a novel kringle-containing transmembrane protein. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1518:63-72. [PMID: 11267660 DOI: 10.1016/s0167-4781(01)00168-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Kringle domain, a triple-disulfide-linked domain, is conserved in diverse proteins which play important roles in various biological processes. We cloned Kremen, a novel member of kringle-containing proteins, using a newly developed unique strategy, 'Kringle-SAGE (serial analysis of gene expression)', which enables comprehensive analysis of kringle-containing proteins. Kremen is likely to be a type-I transmembrane protein composed of 473 amino acid residues. Kremen has a kringle domain, a WSC domain, and CUB domains in the extracellular region, while the intracellular region has no conserved motif involved in signal transduction. In the mouse embryo, the Kremen mRNA level, which was increased during embryonic development, was localized in the apical ectodermal ridge of limb buds, myotome, and sensory organs (e.g. optic vesicle, otic vesicle, nasal pit). In the adult mouse, Kremen mRNA was expressed in a variety of tissues with a relatively strong expression in the lung, heart, and skeletal muscle. Kremen mRNA expression in C2C12 and NIE-115 cells increased during respective differentiation into muscular and neural cells. These results suggest a potential role for Kremen in the regulation of cellular responses upon extracellular stimulus or cell-cell interaction in neuronal and/or muscle cells. Kringle-SAGE is expected to facilitate further elucidation of structure and functions of kringle proteins.
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Affiliation(s)
- T Nakamura
- Division of Biochemistry, Department of Oncology, Biomedical Research Center, Osaka University Graduate School of Medicine, Suita, 565-0871, Osaka, Japan.
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30
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Ip FC, Glass DG, Gies DR, Cheung J, Lai KO, Fu AK, Yancopoulos GD, Ip NY. Cloning and characterization of muscle-specific kinase in chicken. Mol Cell Neurosci 2000; 16:661-73. [PMID: 11083926 DOI: 10.1006/mcne.2000.0892] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Muscle-specific kinase (MuSK) is part of the receptor complex that is involved in the agrin-induced formation of the neuromuscular junction. In the rodent, prominent mRNA expression of MuSK is restricted to skeletal muscle while the expression of agrin can also be detected in brain and certain nonneuronal tissues. The recent identification of Xenopus MuSK reveals that MuSK can be detected in tissues other than skeletal muscle, such as the neural tube, eye vesicles, and spleen. In this study, we describe the cloning and characterization of the chicken ortholog of MuSK and demonstrate that the regulation of MuSK expression in muscle is conserved from avian to rodent. Abundant mRNA expression of MuSK can be detected in early embryonic chick muscle and is up-regulated after nerve injury. More importantly, we also demonstrate that, in the chicken, MuSK mRNA is expressed during development in brain and liver, suggesting possible novel functions for MuSK. Furthermore, the regulatory profile of MuSK expression in chick muscle closely parallels that observed for acetylcholine receptor, in terms of both mRNA expression and protein localization. Finally, studies with paralyzed chicken muscle as well as with cultured chick myotubes demonstrate the dependence of MuSK on both electrical activity and trophic factors.
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MESH Headings
- Animals
- Cells, Cultured
- Chick Embryo
- Chickens/genetics
- Cloning, Molecular
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Enzymologic
- Molecular Sequence Data
- Muscle Denervation
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/enzymology
- Muscle, Skeletal/cytology
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/innervation
- Nerve Crush
- Paralysis/chemically induced
- Protein Structure, Tertiary
- Protein-Tyrosine Kinases/chemistry
- Protein-Tyrosine Kinases/genetics
- Rats
- Receptor Protein-Tyrosine Kinases/chemistry
- Receptor Protein-Tyrosine Kinases/genetics
- Receptors, Cholinergic
- Sciatic Nerve/physiology
- Sequence Homology, Amino Acid
- Species Specificity
- Tetrodotoxin/pharmacology
- Transcription, Genetic/physiology
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Affiliation(s)
- F C Ip
- Department of Biochemistry and Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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31
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Godfrey EW, Roe J, Heathcote RD. Agrin fragments differentially induce ectopic aggregation of acetylcholine receptors in myotomal muscles ofXenopus embryos. ACTA ACUST UNITED AC 2000. [DOI: 10.1002/1097-4695(20000915)44:4<436::aid-neu6>3.0.co;2-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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Zhou H, Glass DJ, Yancopoulos GD, Sanes JR. Distinct domains of MuSK mediate its abilities to induce and to associate with postsynaptic specializations. J Cell Biol 1999; 146:1133-46. [PMID: 10477765 PMCID: PMC2169478 DOI: 10.1083/jcb.146.5.1133] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Agrin released from motor nerve terminals activates a muscle-specific receptor tyrosine kinase (MuSK) in muscle cells to trigger formation of the skeletal neuromuscular junction. A key step in synaptogenesis is the aggregation of acetylcholine receptors (AChRs) in the postsynaptic membrane, a process that requires the AChR-associated protein, rapsyn. Here, we mapped domains on MuSK necessary for its interactions with agrin and rapsyn. Myotubes from MuSK(-/)- mutant mice form no AChR clusters in response to agrin, but agrin-responsiveness is restored by the introduction of rat MuSK or a Torpedo orthologue. Thus, MuSK(-/)- myotubes provide an assay system for the structure-function analysis of MuSK. Using this system, we found that sequences in or near the first of four extracellular immunoglobulin-like domains in MuSK are required for agrin responsiveness, whereas sequences in or near the fourth immunoglobulin-like domain are required for interaction with rapsyn. Analysis of the cytoplasmic domain revealed that a recognition site for the phosphotyrosine binding domain-containing proteins is essential for MuSK activity, whereas consensus binding sites for the PSD-95/Dlg/ZO-1-like domain-containing proteins and phosphatidylinositol-3-kinase are dispensable. Together, our results indicate that the ectodomain of MuSK mediates both agrin- dependent activation of a complex signal transduction pathway and agrin-independent association of the kinase with other postsynaptic components. These interactions allow MuSK not only to induce a multimolecular AChR-containing complex, but also to localize that complex to a primary scaffold in the postsynaptic membrane.
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Affiliation(s)
- Heather Zhou
- Washington University School of Medicine, St. Louis, Missouri 63110
| | | | | | - Joshua R. Sanes
- Washington University School of Medicine, St. Louis, Missouri 63110
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Fu AK, Cheung WM, Ip FC, Ip NY. Identification of genes induced by neuregulin in cultured myotubes. Mol Cell Neurosci 1999; 14:241-53. [PMID: 10576892 DOI: 10.1006/mcne.1999.0784] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The formation of the neuromuscular junction (NMJ) involves a series of inductive interactions between motor neurons and muscle fibers. The neural signals proposed to induce the mRNA expression of acetylcholine receptors in muscle include neuregulin (NRG). In the present study, we have employed RNA fingerprinting by arbitrarily primed PCR analysis to identify the differentially expressed transcripts following NRG treatment in cultured myotubes. Nine partial cDNA fragments were isolated; the mRNA expression of eight of these genes was found to be up-regulated by NRG. The spatial and temporal expression profiles of these NRG-regulated genes in rat tissues during development suggest potential functional roles during the formation of NMJ in vivo. Our findings not only allowed the identification of novel genes, but also suggested possible functions for some known genes that are consistent with their potential roles at the NMJ. Furthermore, the identification of G-protein beta1 subunit and G-protein-coupled receptor as NRG-regulated genes has provided the first demonstration that activation of the NRG signaling pathway can induce the expression of components in the G-protein signaling cascade.
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Affiliation(s)
- A K Fu
- Department of Biology and Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, China
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