Subunit composition, molecular environment, and activation of native TRPC channels encoded by their interactomes

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Transient Receptor Potential Canonical (TRPC) channels are crucial Ca2+-permeable cation channels in the mammalian brain.
• TRPC channels regulate vital neuronal functions including growth, synapse formation, neurotransmitter release, and synaptic plasticity.
• The precise molecular architecture and assembly of native TRPC channels have remained largely undefined.

Purpose of the Study:

• To elucidate the molecular composition and assembly of native TRPC channels in the rodent brain.
• To understand the interactome and stoichiometry of TRPC channel complexes.
• To resolve the molecular basis of TRPC channel activation.

Main Methods:

• High-resolution proteomics was employed to analyze native TRPC channel complexes.
• Mass spectrometry-based proteomics identified interacting proteins and determined complex stoichiometry.
• Biochemical assays were used to investigate specific protein-protein interactions.

Main Results:

• Native TRPC channels form large macromolecular complexes (>1 MDa) in the rodent brain.
• TRPC1, TRPC4, and TRPC5 channels primarily exist as heteromers with defined subunit stoichiometries.
• TRPC3, TRPC6, and TRPC7 channels predominantly form homomers.
• TRPC1/C4/C5 channels can co-assemble with metabotropic glutamate receptor 1 (mGluR1).

Conclusions:

• The study reveals the specific subunit composition of native TRPC channels, differentiating between heteromeric and homomeric assemblies.
• TRPC channel complexes are intricate structures involving co-assembled proteins that ensure specific and reliable activation.
• These findings provide a molecular framework for understanding TRPC channel function and regulation in the brain.