Cloning and expression of SEZ-6, a brain-specific and seizure-related cDNA.

To clarify the molecular mechanism of neuronal bursting activity of seizures, we have constructed a cDNA library from mouse cerebrum cortex-derived cells treated with pentylentetrazole (PTZ), one of the convulsant drugs. Using a differential screening technique, several cDNA clones whose expressions change with PTZ-treatment were obtained. Among these clones, SEZ-6 was characterized by increased expression with PTZ. Detailed northern analysis showed that expression of SEZ-6 was limited to the brain and increased by the administration of PTZ not only in in vitro cultured cells but also in vivo. Analysis of SEZ-6 cDNA revealed multiple motifs, including typical signal sequence, threonine-rich domain, five copies of short consensus repeats (SCRs) or sushi domain (complement C3b/C4b binding site), two repeated sequences which were partially similar to the CUB domain or complement C1r/s-like repeat, one transmembrane domain and a short cytoplasmic segment in the C-terminal region. Although many proteins with multiple SCRs or CUB domains other than complement-related proteins have been found, this is the first report about a brain-specific cDNA which encodes membrane protein with both SCRs and CUB domain-like segments. Based on these findings, it is evident that SEZ-6 encodes a novel type of protein which may be related to seizure.