Gating of Pannexin 1‐Mediated ATP Release Channels by Mechanical Stress Stimuli

Abstract

Most cells release ATP to extracellular compartments wherein ATP acts as a signaling molecule to regulate responses such as vasodilation and inflammatory activation. Pannexin‐1 (Panx1) hemichannels have been proposed as major conduits for ATP efflux in response to proapoptotic stimulation or mechanical deformation of the plasma membrane. Recent studies have demonstrated that caspase‐mediated cleavage of the Panx1 C‐terminus is a novel gating mechanism for this channel in apoptotic cells. In this study we examine the possible role of caspases or other proteases in the acute ATP release induced by non‐apoptotic mechanical stress stimuli in rat C6 glioma cells (which lack native Panx1) versus C6 cells stably transfected with Panx1 (C6‐Panx1). C6 cells were mechanically stimulated by medium exchange or by thrombin (which triggers rapid reorganization of the actin cytoskeleton) to elicit acute ATP release. Only minor ATP release was observed in control C6 cells in response to either medium exchange or thrombin addition. In contrast, medium exchange triggered robust ATP release from C6‐Panx1 cells. Current experiments are testing whether thrombin triggers similar ATP release in C6‐Panx1 cells and whether proteolysis of Panx1 mediates gating of these ATP release channels in response to mechanical stimulation.