Design of Super-arrestins for Gene Therapy of Diseases Associated with Excessive Signaling of G Protein-Coupled Receptors

Numerous congenital disorders, ranging from night blindness to cancer, are associated with signaling by overactive GPCR mutants. Excessive GPCR signaling also underlies certain acquired pathological conditions. The coupling of most GPCRs to their cognate G proteins is stopped by the natural desensitization mechanism, which includes receptor phosphorylation by GRKs followed by arrestin binding to active phosphoreceptor. Elucidation of the molecular mechanisms of arrestin binding to GPCRs enabled the construction of enhanced arrestins that bind active receptors with higher affinity and even interact with unphosphorylated GPCRs. These mutants have therapeutic potential due to their ability to compensate, reducing excessive activity of mutant and normal GPCRs. The feasibility of this compensational approach was demonstrated in rod photoreceptors predominantly expressing only one receptor, rhodopsin, and visual arrestin-1. Mammals have two nonvisual arrestins, which are fairly promiscuous, interacting with hundreds of GPCR subtypes. Identification of arrestin elements responsible for their receptor preference enables the construction of nonvisual arrestins specifically targeting particular receptors. This allows the construction of enhanced receptor-specific mutants for targeted suppression of signaling by one GPCR, but not others expressed by the same cell. Modification of elements responsible for the interactions with non-receptor partners creates signaling-biased arrestins that direct the signaling to the pathways of choice, further expanding potential therapeutic uses of “designer” arrestins.