Differential expression of isoforms of PSD · 95 binding protein ( GKAP / SAPAPl ) during rat brain development

PSD-95/SAP90, which binds to the C-terminus of NMDA receptor and Shaker-type potassium channel, is one of the major postsynaptic density proteins. Recently, novel class of proteins interacting with the guanylate kinase domain of PSD-95 have been identified, guanylate kinaseassociated protein (GKAP) and SAP90/PSD-95-associated proteins (SAPAPs). Here we report the isolation of new isoforms of PSD-95 binding protein (GKAP/SAPAPl) using the yeast two-hybrid system. The isolated protein directly interacts with the guanylate kinase domain of PSD-95. Northern blot analyses reveal that the expression of these isoforms containing distinct N-terminal sequences is differentially regulated during brain development. The present findings suggest that each isoform of the PSD-95 binding protein is differentially expressed in a development-dependent manner and may be involved in the complex formation of PSD-95 and channeVreceptors at the postsynaptic density.