Molecular details of ruthenium red pore block in TRPV channels

Area of Science:

• Molecular biology
• Biophysics
• Structural biology

Background:

• Transient receptor potential vanilloid (TRPV) channels are crucial for calcium homeostasis, pain, immunity, and cancer.
• Ruthenium red (RR) is a known blocker of various cation channels, including TRPV channels.

Purpose of the Study:

• To elucidate the molecular mechanisms of ruthenium red (RR) block in TRPV2 and TRPV5 channels using cryo-electron microscopy.
• To understand the structural basis of ion flow regulation and channel gating in different TRPV subfamilies.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to determine high-resolution structures.
• TRPV2 and TRPV5 channels were studied in activated states with specific activators.

Main Results:

• In TRPV2, RR binds within the open selectivity filter, inhibiting ion flux and preventing inactivation.
• In TRPV5, RR blocks the selectivity filter and closes the lower gate via interactions with pore vestibule residues.
• Detailed structural insights into RR's interaction with distinct TRPV channel architectures were obtained.

Conclusions:

• Ruthenium red binding mechanisms differ between TRPV2 and TRPV5, highlighting subfamily-specific pore block.
• The study reveals the dynamic nature of the TRPV selectivity filter and allosteric communication between the filter and lower gate.
• These findings advance the understanding of TRPV channel function and regulation by pore blockers.