The Journal of Cell Biology, Vol 107, 267-278, Copyright © 1988 by The Rockefeller University Press

ARTICLES

Regulation of agrin-induced acetylcholine receptor aggregation by Ca++ and phorbol ester

BG Wallace
Department of Neurobiology, Stanford University School of Medicine, California 94305.

Agrin, a protein extracted from the electric organ of Torpedo californica, induces the formation of specializations on cultured chick myotubes that resemble the postsynaptic apparatus at the neuromuscular junction. The aim of the studies reported here was to characterize the effects of agrin on the distribution of acetylcholine receptors (AChRs) and cholinesterase as a step toward determining agrin's mechanism of action. When agrin was added to the medium bathing chick myotubes small (less than 4 micron 2) aggregates of AChRs began to appear within 2 h and increased rapidly in number until 4 h. Over the next 12-20 h the number of aggregates per myotube decreased as the mean size of each aggregate increased to approximately 15 micron 2. The accumulation of AChRs into agrin-induced aggregates occurred primarily by lateral migration of AChRs already in the myotube plasma membrane at the time agrin was added to the cultures. Aggregates of AChRs and cholinesterase remained as long as agrin was present in the medium; if agrin was removed the number of aggregates declined slowly. The formation and maintenance of agrin-induced AChR aggregates required Ca++, Co++ and Mn++ inhibited agrin-induced AChR aggregation and increased the rate of aggregate dispersal. Mg++ and Sr++ could not substitute for Ca++. Agrin- induced receptor aggregation also was inhibited by phorbol 12-myristate 13-acetate, an activator of protein kinase C, and by inhibitors of energy metabolism. The similarities between agrin's effects on cultured myotubes and events that occur during formation of neuromuscular junctions support the hypothesis that axon terminals release molecules similar to agrin that induce the differentiation of the postsynaptic apparatus.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

• Henriquez, J. P., Webb, A., Bence, M., Bildsoe, H., Sahores, M., Hughes, S. M., Salinas, P. C. (2008). Wnt signaling promotes AChR aggregation at the neuromuscular synapse in collaboration with agrin. Proc. Natl. Acad. Sci. USA 105: 18812-18817 [Abstract] [Full Text]  
• Scotton, P., Bleckmann, D., Stebler, M., Sciandra, F., Brancaccio, A., Meier, T., Stetefeld, J., Ruegg, M. A. (2006). Activation of Muscle-specific Receptor Tyrosine Kinase and Binding to Dystroglycan Are Regulated by Alternative mRNA Splicing of Agrin. J. Biol. Chem. 281: 36835-36845 [Abstract] [Full Text]  
• Zhu, D., Xiong, W. C., Mei, L. (2006). Lipid rafts serve as a signaling platform for nicotinic acetylcholine receptor clustering.. J. Neurosci. 26: 4841-4851 [Abstract] [Full Text]  
• y Valenzuela, I. M.-P., Hume, R. I., Krejci, E., Akaaboune, M. (2005). In Vivo Regulation of Acetylcholinesterase Insertion at the Neuromuscular Junction. J. Biol. Chem. 280: 31801-31808 [Abstract] [Full Text]  
• Trinidad, J. C., Cohen, J. B. (2004). Neuregulin Inhibits Acetylcholine Receptor Aggregation in Myotubes. J. Biol. Chem. 279: 31622-31628 [Abstract] [Full Text]  
• Tseng, C.-N., Zhang, L., Cascio, M., Wang, Z.-Z. (2003). Calcium Plays a Critical Role in Determining the Acetylcholine Receptor-clustering Activities of Alternatively Spliced Isoforms of Agrin. J. Biol. Chem. 278: 17236-17245 [Abstract] [Full Text]  
• Nelson, P. G., Jia, M., Li, M.-X. (2003). Protein Kinases and Hebbian Function. Neuroscientist 9: 110-116 [Abstract]  
• Borges, L. S., Ferns, M. (2001). Agrin-Induced Phosphorylation of the Acetylcholine Receptor Regulates Cytoskeletal Anchoring and Clustering. JCB 153: 1-12 [Abstract] [Full Text]  
• Briguet, A., Ruegg, M. A. (2000). The Ets Transcription Factor GABP Is Required for Postsynaptic Differentiation In Vivo. J. Neurosci. 20: 5989-5996 [Abstract] [Full Text]  
• Burkin, D., Kim, J., Gu, M, Kaufman, S. (2000). Laminin and alpha7beta1 integrin regulate agrin-induced clustering of acetylcholine receptors. J. Cell Sci. 113: 2877-2886 [Abstract]  
• Hilgenberg, L. G. W., Hoover, C. L., Smith, M. A. (1999). Evidence of an Agrin Receptor in Cortical Neurons. J. Neurosci. 19: 7384-7393 [Abstract] [Full Text]  
• Cornish, T, Chi, J, Johnson, S, Lu, Y, Campanelli, J. (1999). Globular domains of agrin are functional units that collaborate to induce acetylcholine receptor clustering. J. Cell Sci. 112: 1213-1223 [Abstract]  
• Montanaro, F., Gee, S. H., Jacobson, C., Lindenbaum, M. H., Froehner, S. C., Carbonetto, S. (1998). Laminin and alpha -Dystroglycan Mediate Acetylcholine Receptor Aggregation via a MuSK-Independent Pathway. J. Neurosci. 18: 1250-1260 [Abstract] [Full Text]  
• Megeath, L. J., Fallon, J. R. (1998). Intracellular Calcium Regulates Agrin-Induced Acetylcholine Receptor Clustering. J. Neurosci. 18: 672-678 [Abstract] [Full Text]  
• Denzer, A. J., Brandenberger, R., Gesemann, M., Chiquet, M., Ruegg, M. A. (1997). Agrin Binds to the Nerve-Muscle Basal Lamina via Laminin. JCB 137: 671-683 [Abstract] [Full Text]  
• Martin, P., Sanes, J. (1997). Integrins mediate adhesion to agrin and modulate agrin signaling. Development 124: 3909-3917 [Abstract]  
• Kirsch, J., Kroger, S. (1996). {blacksquare} REVIEW : Postsynaptic Anchoring of Receptors: A Cellular Approach to Neuronal and Muscular Sensitivity. Neuroscientist 2: 100-108 [Abstract]  
• Campanelli, J., Gayer, G., Scheller, R. (1996). Alternative RNA splicing that determines agrin activity regulates binding to heparin and alpha-dystroglycan. Development 122: 1663-1672 [Abstract]  
• Hilgenberg, L, Miles, K (1995). Developmental regulation of a protein kinase C isoform localized in the neuromuscular junction. J. Cell Sci. 108: 51-61 [Abstract]  
• McMahan, U.J. (1990). The Agrin Hypothesis. Cold Spring Harb Symp Quant Biol 55: 407-418 [Abstract]  

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents