We next assessed whether GIRK2a and GIRK2c proteins are present in mouse hippocampus and cultured hippocampal neurons. A commercially-available GIRK2 antibody (pan-GIRK2) targeting a domain in both isoforms revealed a doublet in intact hippocampus and cultured hippocampal neurons from wild-type but not Girk2 −/− mice (Fig. 2B). We also used a custom GIRK2c-specific antibody, raised against the unique 11-amino acid domain of GIRK2c, to probe for the GIRK2c isoform in hippocampal samples. The GIRK2c antibody recognized GIRK2c, but not other GIRK subunits, when expressed in HEK cells (Supplementary Fig. S1). In hippocampal samples, this antibody revealed a single band that aligned with the upper band in the doublet seen with the pan-GIRK2 antibody (Fig. 2B). Thus, two GIRK2 splice isoform proteins are present in the mouse hippocampus, one definitively identified as GIRK2c and the other exhibiting an electrophoretic mobility consistent with that of GIRK2a.
