Effects of TRPC1's Lysines on Heteromeric TRPC5-TRPC1 Channel Function

Area of Science:

• Ion channel physiology
• Molecular and cellular neuroscience
• Cardiovascular research

Background:

• Transient Receptor Potential Canonical (TRPC) proteins, including TRPC5, form plasma membrane cation channels crucial for nervous and cardiovascular systems.
• TRPC5 channel activation increases neuronal excitability, while TRPC1 acts as an inhibitor through heteromerization, but the precise inhibitory mechanism remains unclear.

Purpose of the Study:

• To investigate the role of subunit stoichiometry and specific charged residues in TRPC1's inhibitory function on TRPC5/TRPC1 heteromeric channels.
• To elucidate the molecular basis for TRPC1-mediated inhibition of TRPC5 channel activity.

Main Methods:

• Electrophysiological techniques were employed to assess TRPC5/TRPC1 heteromer function under varying subunit compositions.
• Molecular dynamics simulations were performed to analyze the structural interactions within the TRPC5/TRPC1 channel pore.
• Site-directed mutagenesis was used to substitute key lysine residues in TRPC1.

Main Results:

• Increased TRPC1 expression in TRPC5/TRPC1 heteromers significantly reduced histamine-induced cation influx.
• Molecular dynamics simulations identified two positively charged lysine residues in TRPC1 facing the heteromeric pore lumen.
• Mutating these lysines diminished TRPC1's inhibitory effect, suggesting their role in regulating cation flow.
• Extracellular Mg2+ was found to inhibit cation influx through TRPC5/TRPC1 channels.

Conclusions:

• The inhibitory action of TRPC1 on TRPC5/TRPC1 heteromeric channel function is mediated by positively charged lysine residues located within the channel pore lumen.
• These findings provide critical insights into the regulation of TRPC5/TRPC1 channel activity and potential therapeutic targets.