INTERACTIVE CLONING WITH THE SH3 DOMAIN OF N-SRC IDENTIFIES A NEW BRAIN-SPECIFIC ION-CHANNEL PROTEIN, WITH HOMOLOGY TO EAG AND CYCLIC NUCLEOTIDE-GATED CHANNELS

We have isolated a novel cDNA, that appears to represent a new class o f ion channels, by using the yeast two-hybrid system and the SH3 domai n of the neural form of Src (N-src) as a bait. The encoded polypeptide , BCNG-1, is distantly related to cyclic nucleotide-gated channels and the voltage-gated channels, Eag and H-erg, BCNG-1 is expressed exclus ively in the brain, as a glycosylated protein of approximate to 132 kD a. Immunohistochemical analysis indicates that BCNG-1 is preferentiall y expressed in specific subsets of neurons in the neocortex, hippocamp us, and cerebellum, in particular pyramidal neurons and basket cells. Within individual neurons, the BCNG-1 protein is localized to either t he dendrites or the axon terminals depending on the cell type. Souther n blot analysis shows that several other BCNG-related sequences are pr esent in the mouse genome, indicating the emergence of an entire subfa mily of ion channel coding genes. These findings suggest the existence of a new type of ion channel, which is potentially able to modulate m embrane excitability in the brain and could respond to regulation by c yclic nucleotides.