Abstract 174: Regulation of Kv11.1 C-terminal Isoform Expression by Polypyrimidine Tract Binding Protein
The KCNH2 gene encodes the Kv11.1 potassium channel that conducts the rapidly activating delayed rectifier current in the heart. KCNH2 pre-mRNA undergoes alternative processing. Intron 9 splicing leads to the formation of a functional, full-length Kv11.1a isoform, and polyadenylation within intron 9 generates a non-functional, C-terminally truncated Kv11.1a-USO isoform. In this study we investigated the developmental regulation of Kv11.1 isoform expression. We showed that Kv11.1a expression was lower than that of Kv11.1a-USO in the adult heart, but the levels of Kv11.1a and Kv11.1a-USO were similar in the fetal heart. We studied the effect of polypyrimidine tract binding protein (PTB) on the alternative processing of KCNH2 pre-mRNA. PTB is an RNA-binding protein well known for its role in the regulation of alternative splicing. Recently, PTB has been shown to regulate polyadenylation. We showed that PTB increased Kv11.1a isoform expression and decreased Kv11.1a-USO isoform expression by the RNase protection assay and immunoblot analysis. In patch-clamp experiments, we found that PTB significantly increased Kv11.1 current. Our findings suggest that the relative expression of Kv11.1 C-terminal isoforms can be regulated by PTB. It has been reported that PTB protein abundance is progressively reduced during postnatal heart development. Thus, PTB may play an important role in developmental regulation of Kv11.1 isoform expression in the heart.