Molecular determinants for subcellular localization of PSD-95 with an interacting K+ channel

ion channels and PSD-95 are colocalized in specific neuronal subcellular lo cations by an unknown mechanism. To investigate mechanisms of localization, we used biolistic techniques to express GFP-tagged PSD-95 (PSD-95:GFP) and the K+-selective channel Kv1.4 in slices of rat cortex. In pyramidal cells , PSD-95:GFP required a single PDZ domain and a region including the SH3 do main for localization to postsynaptic sites. When transfected alone, PSD-95 :GFP was present in dendrites but absent from axons. When cotransfected wit h Kv1.4, PSD-95:GFP appeared in both axons and dendrites, while Kv1.4 was r estricted to axons. When domains that mediate the interaction of Kv1.4 and PSD-95 were disrupted, Kv1.4 localized nonspecifically. Our results provide evidence that Kv1.4 itself may determine its subcellular location, while a n associated MAGUK protein is a necessary but not sufficient cofactor.