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Background
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The members of the SAP90/PSD-95-associated protein (SAPAP) family (also known as the DLGAP family) specifically interact with PSD-95/SAP90, a membrane-associated guanylate kinase localized at postsynaptic density (PSD) in neuronal cells. The SAPAP proteins are thought to be adaptor proteins that also interact with different synaptic scaffolding proteins, cytoskeletal and signaling components, such as focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (PYK2). SAPAP1, -2 and -4 mRNA are targeted to cell bodies, whereas SAPAP3 mRNA is detected mainly in cell bodies. SAPAP1 protein however, is targeted to the synapse and is not reliant on the synaptic localization of PSD-95 or the synaptic scaffolding molecule (S-SCAM). SAPAP3 protein is targeted to dendrites. Recent experiments have suggested that SAPAP3 may be involved in obsessive-compulsive disorder (OCD), as mice lacking SAPAP3 exhibited OCD-like symptoms which could be relieved by lentiviral-mediated selective expression of SAPAP3 in the striatum of SAPAP3-mutant mice. Multiple isoforms of the SAPAP proteins are known to exist.
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