An optically controlled probe identifies lipid-gating fenestrations within the TRPC3 channel

Area of Science:

• Biochemistry
• Molecular Biology
• Ion Channel Physiology

Background:

• Transient receptor potential canonical (TRPC) channels, including TRPC3, TRPC6, and TRPC7, are known to interact with the lipid messenger diacylglycerol (DAG).
• The precise mechanisms by which these ion channels detect DAG and undergo lipid-gating remain largely unelucidated.
• Understanding these processes is crucial for deciphering cellular signaling pathways regulated by lipid mediators.

Purpose of the Study:

• To investigate the molecular basis of diacylglycerol (DAG) sensing and lipid-gating in TRPC3 channels.
• To develop a novel tool for precise spatiotemporal control of TRPC3 channel activity using light.
• To identify key structural elements within the TRPC3 channel pore domain responsible for lipid interaction and gating.

Main Methods:

• Generation of a photoactivatable diacylglycerol (DAG) analog, OptoDArG, for light-induced channel modulation.
• Structure-guided mutagenesis screen focusing on the TRPC3 pore domain, particularly residues near the selectivity filter.
• Photochemical control experiments using OptoDArG to induce activation-deactivation cycling of TRPC3 channels.

Main Results:

• OptoDArG enabled efficient light-dependent control over TRPC3 channel activity.
• A single glycine residue at position 652 (G652) in the TRPC3 pore domain was identified as crucial for lipid sensing.
• Mutations at G652 altered the channel's selectivity for different DAG species, and pore domain fenestrations were confirmed as key sites for lipid interaction.
• Optical 'lipid clamp' experiments demonstrated the pivotal role of pore domain fenestrations in the channel's lipid-sensing machinery.

Conclusions:

• A novel mechanism for lipid sensing in TRPC channels has been proposed, involving lateral fenestrations within the pore domain.
• These fenestrations accommodate lipid mediators like DAG, directly influencing channel gating.
• The findings provide critical insights into the molecular basis of TRPC channel regulation by lipid messengers.