The cellular prion protein (PrPC) is a highly conserved protein throughout the evolution of mammals and therefore is thought to play important cellular functions. Despite decades of intensive researches, the physiological function of PrPC remains enigmatic. Differently, in particular pathological contexts, generally referred as transmissible spongiform encephalopathies, a conformational isoform of PrPC, i.e., PrPSc, is considered the causative agent of these diseases. In this study, we investigated putative PrPC cellular functions through the identification of PrPC protein interactants. Using a bacterial two-hybrid approach, we identified a novel interaction between PrPC and a two-pore potassium channel protein, TREK-1. This interaction was further verified in transfected eukaryotic cells using co-immunoprecipitation and confocal microscopic analysis of the fluorescent transfected proteins. Importantly, in the cerebellar cortex, the endogenous PrPC and TREK-1 proteins exhibited co-localization signals in correspondence of the Purkinje cells. Furthermore, a deletion mapping study defined the carboxyl-terminal regions of the two proteins as the possible determinants of the PrPC-TREK-1 interaction. Our results indicated a novel PrPC interacting protein and suggested that this complex might be relevant in modulating a variety of electrophysiological-dependent cellular responses. (c) 2006 Elsevier Inc. All rights reserved.