Figure 2.

Functional roles of A-to-I RNA editing in the neurotransmitter receptor and the ion channel. (A) The A-to-I editing site (Q/R) in the secondary structure of the GluA2 pre-mRNA regions (top). The schematic of the GluA2 subunit structure and the functional difference in edited and unedited forms (middle and bottom, respectively). RNA editing alters the glutamate residue (Q) (middle left) at the 607th position to a positively charged arginine residue (R) (middle right), which can dramatically reduce calcium permeability (bottom). (B) The five editing sites (A-E) in the secondary structure of the 5HT_2CR pre-mRNA regions where exon 5 base-pairs with the intron 5 (top). The schematic drawing of 5-HT_2c receptor structure the functional difference in edited and unedited forms (middle and bottom, respectively). RNA editing of 5HT_2C receptor converts amino acid isoleucine (I) at 156th position to valine (V), or methionine (M), asparagine (N) at 158th position to aspartic acid (D), serine (S), or glycine (G), and isoleucine (I) at 160th position to valine (V) (middle). Edited 5HT_2CR isoforms exhibit reduced G protein coupling efficiency (bottom left) in comparison to the unedited isoform (bottom right). (C) The A-to-I editing site (I/V) in the secondary structure of Kv1.1 mRNAs (top). The schematic drawing of Kv1.1 channel structure and the functional difference in edited and unedited forms (middle and bottom, respectively) The transmembrane voltage sensor (S4), the K⁺ ion selectivity filter (S5–S6) are indicated in the middle and bottom figure. Editing of Kv1.1 changes the isoleucine (I) (middle) to valine (V) (bottom). which reduces the affinity for the binding of Kv β1.1 and enhances recovery from inactivation