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Santamaria F, Gonzalez J, Augustine GJ, Raghavachari S. Quantifying the effects of elastic collisions and non-covalent binding on glutamate receptor trafficking in the post-synaptic density. PLoS Comput Biol 2010; 6:e1000780. [PMID: 20485563 PMCID: PMC2869312 DOI: 10.1371/journal.pcbi.1000780] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Accepted: 04/09/2010] [Indexed: 11/19/2022] Open
Abstract
One mechanism of information storage in neurons is believed to be determined by the strength of synaptic contacts. The strength of an excitatory synapse is partially due to the concentration of a particular type of ionotropic glutamate receptor (AMPAR) in the post-synaptic density (PSD). AMPAR concentration in the PSD has to be plastic, to allow the storage of new memories; but it also has to be stable to preserve important information. Although much is known about the molecular identity of synapses, the biophysical mechanisms by which AMPAR can enter, leave and remain in the synapse are unclear. We used Monte Carlo simulations to determine the influence of PSD structure and activity in maintaining homeostatic concentrations of AMPARs in the synapse. We found that, the high concentration and excluded volume caused by PSD molecules result in molecular crowding. Diffusion of AMPAR in the PSD under such conditions is anomalous. Anomalous diffusion of AMPAR results in retention of these receptors inside the PSD for periods ranging from minutes to several hours in the absence of strong binding of receptors to PSD molecules. Trapping of receptors in the PSD by crowding effects was very sensitive to the concentration of PSD molecules, showing a switch-like behavior for retention of receptors. Non-covalent binding of AMPAR to anchored PSD molecules allowed the synapse to become well-mixed, resulting in normal diffusion of AMPAR. Binding also allowed the exchange of receptors in and out of the PSD. We propose that molecular crowding is an important biophysical mechanism to maintain homeostatic synaptic concentrations of AMPARs in the PSD without the need of energetically expensive biochemical reactions. In this context, binding of AMPAR with PSD molecules could collaborate with crowding to maintain synaptic homeostasis but could also allow synaptic plasticity by increasing the exchange of these receptors with the surrounding extra-synaptic membrane. One of the most accepted theories of information storage in neurons is that it is partially localized in the strength of synaptic contacts. Evidence suggests that at the cellular level, in combination with other cellular mechanisms, this is implemented by increasing or decreasing the concentration of a particular type of membrane molecules. Two opposing mechanisms have to coexist in synapses to allow them to store information. On one hand, synapses have to be flexible, to allow the storage of new memories. On the other hand, synapses have to be stable to preserve previously learned information. Although much is known about the molecular identity of synapses, the biophysical mechanisms by which molecules can enter, leave and remain in the synapse are unclear. Our modeling work uses fundamental biophysical principles to quantify the effects of molecular collisions and biochemical reactions. Our results show that molecular collisions alone, between the diffusing proteins with anchored molecules in the synapse, can replicate known experimental results. Molecular collision in combination with biochemical binding can be fundamental biophysical principles used by synapses for the formation and preservation of memories.
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Affiliation(s)
- Fidel Santamaria
- Biology Department, The University of Texas at San Antonio, San Antonio, Texas, United States of America
- Neurosciences Institute, The University of Texas at San Antonio, San Antonio, Texas, United States of America
- * E-mail: (FS); (SR)
| | - Jossina Gonzalez
- Biology Department, The University of Texas at San Antonio, San Antonio, Texas, United States of America
| | - George J. Augustine
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Sridhar Raghavachari
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail: (FS); (SR)
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Kitaura J, Song J, Tsai M, Asai K, Maeda-Yamamoto M, Mocsai A, Kawakami Y, Liu FT, Lowell CA, Barisas BG, Galli SJ, Kawakami T. Evidence that IgE molecules mediate a spectrum of effects on mast cell survival and activation via aggregation of the FcepsilonRI. Proc Natl Acad Sci U S A 2003; 100:12911-6. [PMID: 14569021 PMCID: PMC240718 DOI: 10.1073/pnas.1735525100] [Citation(s) in RCA: 215] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We demonstrate that binding of different IgE molecules (IgEs) to their receptor, FcepsilonRI, induces a spectrum of activation events in the absence of a specific antigen and provide evidence that such activation reflects aggregation of FcepsilonRI. Highly cytokinergic IgEs can efficiently induce production of cytokines and render mast cells resistant to apoptosis in an autocrine fashion, whereas poorly cytokinergic IgEs induce these effects inefficiently. Highly cytokinergic IgEs seem to induce more extensive FcepsilonRI aggregation than do poorly cytokinergic IgEs, which leads to stronger mast cell activation and survival effects. These effects of both types of IgEs require Syk tyrosine kinase and can be inhibited by FcepsilonRI disaggregation with monovalent hapten. In hybridoma-transplanted mice, mucosal mast cell numbers correlate with serum IgE levels. Therefore, survival effects of IgE could contribute to the pathogenesis of allergic disease.
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MESH Headings
- Animals
- Bone Marrow Cells/cytology
- Bone Marrow Cells/drug effects
- Bone Marrow Cells/immunology
- Cell Survival
- Cells, Cultured
- Cytokines/metabolism
- Female
- Flow Cytometry
- Genes, Reporter
- Histamine/metabolism
- Hybridomas/transplantation
- Immunoglobulin E/immunology
- Interleukin-3/pharmacology
- Leukotrienes/metabolism
- Luciferases/genetics
- Mast Cells/cytology
- Mast Cells/immunology
- Mice
- Mice, Inbred C57BL
- Mice, Inbred Strains
- Mice, Knockout
- Receptors, IgE/deficiency
- Receptors, IgE/genetics
- Receptors, IgE/immunology
- Transcription, Genetic
- Transplantation, Homologous/immunology
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Affiliation(s)
- Jiro Kitaura
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Jinming Song
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Mindy Tsai
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Koichi Asai
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Mari Maeda-Yamamoto
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Attila Mocsai
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Yuko Kawakami
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Fu-Tong Liu
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Clifford A. Lowell
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - B. George Barisas
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Stephen J. Galli
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
| | - Toshiaki Kawakami
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121; Department of Chemistry, Colorado State University, Fort Collins, CO 80523; Departments of Pathology and Immunology and Microbiology, Stanford University School of Medicine, Stanford, CA 94305-5324; National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kanaya, Shizuoka 428-8501, Japan; Department of Laboratory Medicine, University of California, San Francisco, CA 94143-0134; and Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA 95817
- To whom correspondence should be addressed at: La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, CA 92121. E-mail:
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