Emerging Roles of Diacylglycerol-Sensitive TRPC4/5 Channels

Area of Science:

• Molecular biology
• Ion channel physiology
• Cell signaling

Background:

• Transient receptor potential classical or canonical (TRPC) channels, including TRPC4 and TRPC5, are non-selective cation channels.
• TRPC4 and TRPC5 channels are typically activated via phospholipase C (PLC) following Gq/11 protein-coupled receptor activation.
• Their precise activation mechanisms, particularly diacylglycerol (DAG) sensitivity, have been debated due to perceived insensitivity compared to other TRPC channels.

Purpose of the Study:

• To investigate the regulatory role of scaffolding proteins Na⁺/H⁺ exchanger regulatory factor 1 and 2 (NHERF1/2) in TRPC4 and TRPC5 channel activation.
• To elucidate the molecular basis of TRPC4/5 channel gating and DAG sensitivity.
• To explore the potential for all TRPC channels to be DAG sensitive.

Main Methods:

• Analysis of C-terminal interactions between TRPC4/5 channels and NHERF1/2 scaffolding proteins.
• Investigating the dynamic regulation of TRPC4/5 channel DAG sensitivity.
• Characterizing the TRPC4/5-NHERF protein complex.

Main Results:

• NHERF1 and NHERF2 dynamically regulate the DAG sensitivity of TRPC4 and TRPC5 channels.
• Binding of NHERF proteins to the C-terminus of TRPC4/5 suppresses their DAG sensitivity.
• Dissociation of NHERF proteins from TRPC4/5 enables their DAG sensitivity, suggesting a unified DAG sensitivity mechanism across TRPC channels.

Conclusions:

• The NHERF proteins play a crucial role in modulating TRPC4/5 channel activity.
• The findings suggest that all TRPC channels might be sensitive to DAG, challenging previous assumptions.
• Understanding the TRPC4/5-NHERF complex provides new insights into TRPC channel activation and opens avenues for future research into their physiological and pathophysiological roles.