| RED1, better known as ADARB1/ADAR2, is a double‑stranded RNA–specific adenosine deaminase of the ADAR family that catalyzes site‑selective A‑to‑I editing within structured pre‑mRNAs and noncoding RNAs, with particularly high activity in the central nervous system where it fine‑tunes the coding potential, splicing, and stability of transcripts that control excitability, synaptic transmission, and neuronal development. The protein contains multiple N‑terminal double‑stranded RNA‑binding domains that recognize imperfect duplexes in intronic–exonic or UTR regions, and a C‑terminal deaminase domain that positions a target adenosine in a conserved catalytic pocket for hydrolytic deamination to inosine, which is read as guanosine during translation and by many RNA‑binding factors. Editing by RED1/ADARB1 at defined sites in ion channel and receptor transcripts such as GRIA2 (GluA2 Q/R and R/G sites), KCNA1, and other synaptic genes alters amino acid sequence, Ca²⁺ permeability, gating kinetics, and trafficking properties, and also creates or abolishes splice sites and miRNA binding motifs, so the enzyme functions as a post‑transcriptional regulator that shapes neuronal firing properties and network stability rather than as a global, random editor. Bi‑allelic loss‑of‑function variants in ADARB1 identified in multiple families cause a severe developmental and epileptic encephalopathy characterized by early‑onset intractable seizures, microcephaly, global developmental delay, and hypotonia, and patient-derived cells and in silico analyses show that these variants reduce or abolish deaminase activity, leading to widespread RNA hypoediting across canonical ADAR2 sites in brain‑expressed transcripts. The same study and related work demonstrate that disrupted editing of key substrates—including ion channels, synaptic receptors, and synaptic scaffolding proteins—correlates with hyperexcitability and epileptic phenotypes, linking RED1/ADARB1 activity directly to maintenance of excitatory–inhibitory balance and circuit maturation. Broader transcriptome analyses in schizophrenia and other psychiatric disease indicate that ADARB1‑dependent editing is selectively reduced at many neuronal targets, producing hypoediting signatures that overlap with genetic risk loci and synaptic pathways involved in cognition and behavior. |
