Pannexin 1 activation and inhibition is permeant-selective

Area of Science:

• Molecular Biology
• Cell Biology
• Biophysics

Background:

• Pannexin 1 (Panx1) is a large-pore channel involved in cellular communication.
• Its permeability characteristics and how they relate to different molecules are not fully understood.
• Current methods often infer Panx1 activity using fluorescent dye permeability, which may not be accurate.

Purpose of the Study:

• To investigate the permeant selectivity of pannexin 1 (Panx1) channel activation and inhibition.
• To determine if fluorescent dye permeability accurately reflects the passage of other molecules through Panx1.
• To assess the reliability of ethidium uptake as a general indicator of Panx1 channel activity.

Main Methods:

• Utilized Panx1-expressing Xenopus laevis oocytes and HEK293T cells.
• Examined the effects of different Panx1 activation mechanisms (e.g., cell shrinkage, C-terminal truncation, pH changes) on ion and ethidium flux.
• Assessed the potency of Panx1 inhibitors on ion currents versus ethidium uptake.

Main Results:

• Different Panx1 activation methods differentially affected ion and ethidium permeation.
• Cell shrinkage and C-terminal truncation increased ion conductance but not ethidium uptake.
• Extracellular pH changes primarily impacted ethidium permeability, not ion conductance.
• Panx1 showed a preference for anionic permeants like chloride, lactate, and glutamate.
• Panx1 inhibitors were more potent against ion currents than ethidium uptake.

Conclusions:

• Pannexin 1 (Panx1) activation and inhibition exhibit permeant selectivity.
• Ethidium permeability is not a reliable surrogate for the passage of atomic ions or other small biological molecules through Panx1.
• Ethidium uptake should not be used as a general measure of Panx1 channel activity.