FRET-based analysis of TRPC subunit stoichiometry

Area of Science:

• Molecular biology
• Cell biology
• Biophysics

Background:

• Canonical transient receptor potential channels (TRPC) are cation channels involved in various cellular functions.
• TRPC subunits are hypothesized to form homo- or heterotetrameric complexes.
• Previous methods for verifying assembly include coimmunoprecipitation and functional assays.

Purpose of the Study:

• To explore and verify the utility of fluorescence resonance energy transfer (FRET) for studying ion channel subunit assembly.
• To investigate the spatiotemporal dynamics of TRPC subunit assembly.
• To determine the stoichiometry of TRPC complexes.

Main Methods:

• Temporally and spatially resolved FRET imaging in living cells.
• Confocal FRET imaging for high-resolution analysis.
• Quantitative digital video imaging for FRET signal analysis.
• Competition-FRET assays to assess subunit recruitment.

Main Results:

• TRPC subunit assembly occurs early in the endoplasmic reticulum and Golgi apparatus.
• FRET signals are detectable at the plasma membrane with high spatial resolution.
• FRET efficiency shows weak concentration dependence.
• Quantitative FRET analysis confirms tetrameric stoichiometry of TRPC complexes.
• Competition-FRET assays demonstrate the ability of wild-type subunits to recruit fluorescent subunits.

Conclusions:

• FRET is a powerful technique for visualizing and verifying ion channel assembly in real-time and with high resolution.
• TRPC subunits assemble early in their biogenesis pathway.
• TRPC complexes exhibit tetrameric stoichiometry, as confirmed by FRET-based quantitative analysis.