Identification of an Intramolecular Interaction between the SH3 and Guanylate Kinase Domains of PSD-95*
- From the Department of Physiology and Program in Neuroscience, University of California at San Francisco, San Francisco, California 94143-0444
Abstract
Postsynaptic density-95 (PSD-95/SAP-90) is a member of the membrane-associated guanylate kinase (MAGUK) family of proteins that assemble protein complexes at synapses and other cell junctions. MAGUKs comprise multiple protein-protein interaction motifs including PDZ, SH3 and guanylate kinase (GK) domains, and these binding sites mediate the scaffolding function of MAGUK proteins. Synaptic binding partners for the PDZ and GK domains of PSD-95 have been identified, but the role of the SH3 domain remains elusive. We now report that the SH3 domain of PSD-95 mediates a specific interaction with the GK domain. The GK domain lacks a poly-proline motif that typically binds to SH3 domains; instead, SH3/GK binding is a bi-domain interaction that requires both intact motifs. Although isolated SH3 and GK domains can bind in trans, experiments with intact PSD-95 molecules indicate that intramolecular SH3/GK binding dominates and prevents intermolecular associations. SH3/GK binding is conserved in the related Drosophila MAGUK protein DLG but is not detectable for Caenorhabditis elegans LIN-2. Many previously identified genetic mutations of MAGUKs in invertebrates occur in the SH3 or GK domains, and all of these mutations disrupt intramolecular SH3/GK binding.
Footnotes
-
↵* This work was supported by grants (to D. S. B.) from the National Association for Research on Schizophrenia and Depression, the Culpeper and Beckman Foundations, and the National Institutes of Health (R01, GM36017).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.
-
↵‡ A Howard Hughes Predoctoral Fellow.
-
↵§ To whom all correspondence should be addressed: University of California at San Francisco School of Medicine, 513 Parnassus Ave., San Francisco, CA 94143-0444. Tel.: 415-476-6310; Fax: 415-476-4929; E-mail: bredt{at}itsa.ucsf.edu.
- Abbreviations:
- PSD-95
-
postsynaptic density-95
- ALP
-
actinin-associated LIM protein
- MAGUK
-
membrane-associated guanylate kinase
- GK
-
guanylate kinase
- DLG
-
discs large
- PSD
-
postsynaptic density
- GKAP
-
guanylate kinase associated protein
- MAP1A
-
microtubule-associated protein 1A
- GFP
-
green fluorescent protein
- HEK
-
human embryonic kidney
- GST
-
glutathioneS-transferase
- PCR
-
polymerase chain reaction
- ONPG
-
O-nitrophenyl β-d-galactopyranoside
-
- Received November 6, 1998.
- Revision received April 7, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
