cAMP-dependent phosphorylation modulates voltage gating in an endothelial Cl- channel

Area of Science:

• Physiology
• Molecular Biology
• Cell Biology

Background:

• Endothelial cells play a crucial role in vascular function.
• Chloride channels are involved in regulating cell volume and membrane potential.
• Beta-adrenergic signaling impacts vascular tone and endothelial function.

Purpose of the Study:

• To identify and characterize a novel chloride channel in bovine aortic endothelial cells.
• To investigate the functional role of this channel in response to beta-adrenergic stimulation.
• To elucidate the regulatory mechanisms of this chloride channel.

Main Methods:

• Patch clamp electrophysiology (cell-attached, inside-out, outside-out configurations).
• Pharmacological manipulation with isoproterenol and dibutyryl cyclic AMP.
• Analysis of voltage dependence using Boltzmann distribution.
• Assessment of channel block with DIDS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid).

Main Results:

• A voltage-gated, outwardly rectifying, large conductance (400 pS) chloride channel was identified.
• Channel activation observed with isoproterenol and cyclic AMP (cAMP).
• cAMP-dependent phosphorylation shifted the channel's voltage dependence (V1/2) by -50 mV.
• Channel activity was inhibited by DIDS (IC50 ≈ 70 µM).

Conclusions:

• Beta-adrenergic stimulation, via increased intracellular cAMP, likely enhances endothelial cell chloride permeability.
• This effect is mediated by a shift in the chloride channel's voltage dependence, favoring opening at resting membrane potentials.
• The identified channel represents a potential target for modulating endothelial function.