A NOVEL UBIQUITOUSLY DISTRIBUTED ISOFORM OF GIRK2 (GIRK2B) ENHANCES GIRK1 EXPRESSION OF THE G-PROTEIN-GATED K+ CURRENT IN XENOPUS OOCYTES

We have isolated a novel variant form of GIRK2, designated GIRK2B, fro m mouse brain cDNA library. GIRK2B was much shorter than the first typ e of GIRK2 (GIRK2A), but its amino acid sequence was identical to the corresponding part of GIRK2A except the C-terminal eight amino acid re sidues. When GIRK2B cRNA was co-injected with GIRK1 and m(2)-receptor cRNAs to Xenopus oocytes, acetylcholine-induction of the inwardly rect ifying K+ current was enhanced dramatically. This suggests that GIRK2B can form a heteromultimeric G-protein-gated K+ channel with GIRK1. Th e reverse transcription polymerase chain reaction analysis showed that GIRK2B mRNA distributed much more broadly than GIRK1 mRNA. Therefore, GIRK2B might also play other unrecognized roles in various tissues th an to form a K+ channel with GIRK1. (C) 1996 Academic Press, Inc.