Structural basis for diamide modulation of ryanodine receptor.

Area of Science:

• Biochemistry
• Structural Biology
• Insecticide Research

Background:

• Diamide insecticides are globally significant, targeting insect ryanodine receptors (RyRs) for pest control.
• Understanding the molecular mechanisms of diamide action and resistance is crucial for sustainable agriculture and human health.

Purpose of the Study:

• To determine the high-resolution cryo-electron microscopy (cryo-EM) structure of RyR1 in complex with chlorantraniliprole (CHL) in its open state.
• To elucidate the binding site and mechanism of action of diamide insecticides.
• To understand the molecular basis of insecticide resistance and selectivity.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to obtain the 3.2-Å structure of RyR1-CHL complex.
• Mutagenesis studies to validate the CHL binding site and assess insecticide selectivity.
• Analysis of structural data to identify mechanisms of insecticide resistance.

Main Results:

• The highest-resolution cryo-EM structure of an insect RyR1 in the open state bound to chlorantraniliprole (CHL) was determined.
• The CHL binding site was precisely mapped, revealing its interaction with the S4-S5 linker, which triggers channel opening.
• Mutagenesis data confirmed the binding site and explained the selectivity of diamide insecticides for Lepidoptera over other species.
• Two resistance mechanisms in pests were identified: steric hindrance and loss of contact with the insecticide.

Conclusions:

• The detailed structure provides a mechanistic understanding of how diamide insecticides function at the molecular level.
• This research lays the groundwork for designing novel, highly selective diamide pesticides to combat pest resistance.
• The findings also offer insights for developing therapeutic agents targeting human RyRs for myopathies.