Abstract
PSD-95 and SAP97 are scaffolding proteins that have been implicated in regulating AMPA receptor incorporation and function at synapses. Gain- and loss-of-function approaches, however, have generated conflicting results. To minimize adaptations during development and potential dominant-negative effects of overexpression, we have combined silencing of endogenous PSD-95 in mature neurons with heterologous expression of specific SAP97 or PSD-95 isoforms. We find that both PSD-95 and SAP97 contain alternative N termini expressing either double cysteines that normally are palmitoylated (alpha-isoforms) or an L27 domain (beta-isoforms). Whereas alpha-isoforms of PSD-95 and SAP97 influence AMPA receptor-mediated synaptic strength independent of activity, the effects of beta-isoforms are regulated by activity in a CaMKII-dependent manner. Importantly, the synaptic effects of the beta-isoforms are masked by the endogenous alpha-isoform of PSD-95. These results demonstrate that the different N termini of the predominant endogenous forms of PSD-95 (alpha-isoform) and SAP97 (beta-isoform) govern their role in regulating synaptic function.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing / chemistry
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / metabolism*
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Animals
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Calcium-Calmodulin-Dependent Protein Kinase Type 2
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Calcium-Calmodulin-Dependent Protein Kinases / metabolism
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Cells, Cultured
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Cysteine / metabolism
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Disks Large Homolog 4 Protein
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Down-Regulation / genetics
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Gene Silencing / physiology
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Hippocampus / cytology
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Hippocampus / metabolism
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Intracellular Signaling Peptides and Proteins / chemistry
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Membrane Proteins / chemistry
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Neurons / metabolism
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Neurons / physiology
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Organ Culture Techniques
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Protein Isoforms / chemistry
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Protein Isoforms / genetics
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Protein Isoforms / metabolism
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Protein Structure, Tertiary / physiology
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Rats
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Receptors, AMPA / metabolism*
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Synapses / genetics
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Synapses / metabolism*
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Synaptic Transmission / genetics*
Substances
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Adaptor Proteins, Signal Transducing
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Disks Large Homolog 4 Protein
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Dlg1 protein, rat
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Dlg4 protein, rat
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Intracellular Signaling Peptides and Proteins
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Membrane Proteins
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Protein Isoforms
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Receptors, AMPA
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Calcium-Calmodulin-Dependent Protein Kinase Type 2
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Calcium-Calmodulin-Dependent Protein Kinases
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Cysteine