Cyclic GMP-gated channels in a sympathetic neuron cell line

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Physiology

Background:

• Muscarinic agonists stimulate IP3 production, leading to Ca2+ release and activating a cation current in N1E-115 cells.
• Previous studies indicated this current requires cyclic guanosine monophosphate (cGMP) and suggested the presence of cyclic nucleotide-gated (CNG) ion channels.

Purpose of the Study:

• To investigate the presence and properties of CNG channels in N1E-115 cells using patch clamp techniques.
• To determine the role of these channels in neuronal signaling and calcium homeostasis.

Main Methods:

• Utilized patch clamp electrophysiology on differentiated N1E-115 cells.
• Recorded single channel currents in cell-attached and excised patches.
• Applied 8-bromo-cGMP (8-br-cGMP) to activate channels and analyzed dose-response relationships.

Main Results:

• 8-br-cGMP activated Na+-permeable channels in N1E-115 cells.
• cGMP-dependent channel activity exhibited prolonged bursts without desensitization, with activity increasing with cGMP concentration.
• Unitary conductance was 47 pS in 160 mM Na+, independent of voltage, and activation by cGMP showed a Hill coefficient of 2 (apparent KD = 10 µM). cAMP did not activate the channels.
• These CNG channels share properties with those in sensory receptors.

Conclusions:

• N1E-115 cells express functional CNG channels activated by cGMP.
• These channels provide a mechanism for modulating Ca2+ influx and neuronal excitability via the NO/cGMP pathway.
• CNG channels are crucial for refilling intracellular Ca2+ pools during sustained stimulation and may play a similar role in other neurons.