Modulating signalling lifetime to optimise a prototypical animal opsin for optogenetic applications.

Area of Science:

• Optogenetics
• Molecular Biology
• Neuroscience

Background:

• Animal opsins are light-activated G-protein-coupled receptors used for optogenetic research and therapeutics.
• Their utility is limited by slow signal termination, affecting temporal resolution outside native cells.

Purpose of the Study:

• To enhance the temporal resolution of animal opsins, specifically human rod opsin, in heterologous expression systems.
• To investigate strategies for faster signal termination in optogenetic tools.

Main Methods:

• Examined the canonical rhodopsin kinase (GRK1)/visual arrestin pathway for signal termination.
• Utilized phosphorylation-independent arrestin mutants, including tethered versions.
• Introduced point mutations to alter opsin Schiff base stability.
• Applied a successful mutation (E122Q) in a mouse model of retinal degeneration (rd1).

Main Results:

• GRK1 expression had a general suppressive effect on opsin signaling.
• Phosphorylation-independent arrestin mutants, particularly tethered ones, overcame GRK1 suppression.
• Mutations affecting Schiff base stability reduced opsin signaling lifetime.
• Ectopic opsin expression in rd1 mouse retinas showed improved temporal fidelity with the E122Q mutation.

Conclusions:

• Targeting arrestin binding or Schiff-base hydrolysis can yield more time-delimited opsin signaling in heterologous expression.
• These strategies hold potential for improving optogenetic tool performance in research and therapeutic applications.