SAP97 Is Associated with the α-Amino-3-hydroxy-5-methylisoxazole-4-propionic Acid Receptor GluR1 Subunit*
- From the Department of Pharmacology, University of Wisconsin, Madison, Wisconsin 53706-1532 and the ‡Neurobiology Research Center, University of Alabama, Birmingham, Alabama 35213-0021
Abstract
Rapid glutamatergic synaptic transmission is mediated by ionotropic glutamate receptors and depends on their precise localization at postsynaptic membranes opposing the presynaptic neurotransmitter release sites. Postsynaptic localization ofN-methyl-d-aspartate-type glutamate receptors may be mediated by the synapse-associated proteins (SAPs) SAP90, SAP102, and chapsyn-110. SAPs contain three PDZ domains that can interact with the C termini of proteins such asN-methyl-d-aspartate receptor subunits that carry a serine or threonine at the -2 position and a valine, isoleucine, or leucine at the very C terminus (position 0). We now show that SAP97, a SAP whose function at the synapse has been unclear, is associated with α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptors. AMPA receptors are probably tetramers and are formed by two or more of the four AMPA receptor subunits GluR1–4. GluR1 possesses a C-terminal consensus sequence for interactions with PDZ domains of SAPs. SAP97 was present in AMPA receptor complexes immunoprecipitated from detergent extracts of rat brain. After treatment of rat brain membrane fractions with the cross-linker dithiobis(succinimidylpropionate) and solubilization with sodium dodecylsulfate, SAP97 was associated with GluR1 but not GluR2 or GluR3. In vitro experiments with recombinant proteins indicate that SAP97 specifically associates with the C terminus of GluR1 but not other AMPA receptor subunits. Our findings suggest that SAP97 may be involved in localizing AMPA receptors at postsynaptic sites through its interaction with the GluR1 subunit.
Footnotes
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↵* This work was supported by National Institutes of Health Research Grant R01-NS35563 (to J. W. H.) and AG12978 (to C. C. G.), American Heart Association Research Grant 97-GS-74 (to J. W. H.), a Shaw Scientist Award (to J. W. H.), and a grant to the University of Wisconsin Medical School under the Howard Hughes Medical Institute Research Resources Program for Medical Schools.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ To whom correspondence should be addressed: 3770 MSC, 1300 University Avenue, Dept. of Pharmacology, University of Wisconsin, Madison, WI 53706-1532. Tel.: 608-262-0027; Fax: 608-262-1257; E-mail:jwhell{at}facstaff.wisc.edu.
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↵1 The abbreviations used are: NMDA,N-methyl-d-aspartate; AMPA, α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid; DSP, dithiobis(succinimidylpropionate); GRIP, glutamate receptor-interacting protein; GST, glutathione S-transferase; SAP, synapse-associated protein.
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↵2 A. S. Leonard and J. W. Hell, unpublished results.
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- Received March 6, 1998.
- Revision received May 20, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
