Single-channel currents through transient-receptor-potential-like (TRPL) channels.

Area of Science:

• Molecular Biology
• Ion Channel Physiology
• Cellular Electrophysiology

Background:

• Transient Receptor Potential (TRP) channels are crucial for cellular signaling.
• Drosophila TRPL channels, a subtype of TRP channels, have known roles in insects.
• Understanding TRPL channel properties in mammalian cells is essential for comparative physiology.

Purpose of the Study:

• To characterize the biophysical properties of Drosophila TRPL channels expressed in mammalian cells.
• To investigate the modulation of TRPL channel activity by membrane potential and intracellular ions.
• To determine if TRPL channels can function and be modulated in a heterologous mammalian system.

Main Methods:

• Single-channel current recordings in HEK and COS cells expressing recombinant TRPL channels.
• On-cell and inside-out patch-clamp electrophysiology.
• Varying ionic concentrations (Na+, Mg2+, Ca2+, Ba2+) and intracellular guanosine 5'-O-(3-thiotriphosphate) (GTP[gamma-S]) and Ca2+ levels.

Main Results:

• TRPL channels exhibited constitutive activity with specific single-channel conductances (e.g., 104 pS with 115 mM Na+).
• Channel currents reversed near 0 mV, showing linear voltage dependence and cation selectivity.
• Opening probability increased with depolarization, causing outward rectification; activity was enhanced by GTP[gamma-S] and elevated intracellular Ca2+ (>2 microM).
• Constitutively active TRPL channels depolarized host cells, which was reversed by BAPTA chelation.

Conclusions:

• Drosophila TRPL channels expressed in mammalian cells are constitutively active, non-selective cation channels.
• TRPL channel function is modulated by membrane potential and intracellular calcium levels.
• These findings suggest a conserved role and modulation mechanism for TRPL channels across species.