Cypin: A cytosolic regulator of PSD-95 postsynaptic targeting

Bonnie L. Firestein, Jay E. Brenman, Chiye Aoki, Ana M. Sanchez-Perez, Alaa El Din Ei-Husseini, David S. Bredt

Research output: Contribution to journalArticlepeer-review


Postsynaptic density 95 (PSD-95/SAP-90) is a membrane associated guanylate kinase (GK) PDZ protein that scaffolds glutamate receptors and associated signaling networks at excitatory synapses. Affinity chromatography identifies cypin as a major PSD-95-binding protein in brain extracts. Cypin is homologous to a family of hydrolyric bacterial enzymes and shares some similarity with collapsin response mediator protein (CRMP), a cytoplasmic mediator of semaphorin III signalling. Cypin is discretely expressed in neurons and is polarized to basal membranes in intestinal epithelial cells. Overexpression of cypin in hippocampal neurons specifically perturbs postsynaptic trafficking of PSD-95 and SAP-102, an effect not produced by overexpression of other PDZ ligands. In fact, PSD-95 can induce postsynaptic clustering of an otherwise diffusely localized K+ channel, Kv1.4. By regulating postsynaptic protein sorting, cypin may influence synaptic development and plasticity.

Original languageEnglish (US)
Pages (from-to)659-672
Number of pages14
Issue number3
StatePublished - Nov 1999

ASJC Scopus subject areas

  • General Neuroscience


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