Postsynaptic targeting of alternative postsynaptic density-95 isoforms by distinct mechanisms.

Chetkovich DM, Bunn RC, Kuo SH, Kawasaki Y, Kohwi M, Bredt DS
J Neurosci. 2002 22 (15): 6415-25

PMID: 12151521 · PMCID: PMC6758133 · DOI:20026598

Members of the postsynaptic density-95 (PSD95)/synapse-associated protein-90 (SAP90) family of scaffolding proteins contain a common set of modular protein interaction motifs including PDZ (postsynaptic density-95/Discs large/zona occludens-1), Src homology 3, and guanylate kinase domains, which regulate signaling and plasticity at excitatory synapses. We report that N-terminal alternative splicing of PSD95 generates an isoform, PSD95beta that contains an additional "L27" motif, which is also present in SAP97. Using yeast two hybrid and coimmunoprecipitation assays, we demonstrate that this N-terminal L27 domain of PSD-95beta, binds to an L27 domain in the membrane-associated guanylate kinase calcium/calmodulin-dependent serine kinase, and to Hrs, an endosomal ATPase that regulates vesicular trafficking. By transfecting heterologous cells and hippocampal neurons, we find that interactions with the L27 domain regulate synaptic clustering of PSD95beta. Disrupting Hrs-regulated early endosomal sorting in hippocampal neurons selectively blocks synaptic clustering of PSD95beta but does not interfere with trafficking of the palmitoylated isoform, PSD95alpha. These studies identify molecular and functional heterogeneity in synaptic PSD95 complexes and reveal critical roles for L27 domain interactions and Hrs regulated vesicular trafficking in postsynaptic protein clustering.

MeSH Terms (28)

Adaptor Proteins, Signal Transducing Alternative Splicing Amino Acid Motifs Animals Calcium-Calmodulin-Dependent Protein Kinases Cells, Cultured COS Cells Disks Large Homolog 4 Protein Endosomal Sorting Complexes Required for Transport Guanylate Kinases Humans Intracellular Signaling Peptides and Proteins Macromolecular Substances Membrane Proteins Molecular Sequence Data Nerve Tissue Proteins Neurons Nucleoside-Phosphate Kinase Phosphoproteins Precipitin Tests Protein Isoforms Protein Structure, Tertiary Protein Transport Rats Rodentia Sequence Homology, Amino Acid Synapses Two-Hybrid System Techniques

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