Brefeldin A Block of Integrin-dependent Mechanosensitive ATP Release from Xenopus Oocytes Reveals a Novel Mechanism of Mechanotransduction

Many animal cells release ATP into the extracellular medium, and often this release is mechanosensitive. However, the mechanisms underlying this release are not well understood. Using the luciferin-luciferase bioluminescent assay we demonstrate that a Xenopus oocyte releases ATP at a basal rate ∼ 0.01 fmol/s, and gentle mechanical stimulation can increase this to 50 fmol/s. Brefeldin A, nocodazole, and progesterone-induced-maturation block basal and mechanosensitive ATP release. These treatments share the common feature of disrupting the Golgi complex and vesicle trafficking to the cell surface and thereby block protein secretion and membrane protein insertion. We propose that ATP release occurs when protein transport vesicles enriched in ATP fuse with the plasma membrane. Collagenase, integrin-binding peptides, and cytochalasin D also block ATP release, indicating that extracellular, membrane and cytoskeletal elements are involved in the release process. Elevation of intracellular Ca²⁺ does not evoke ATP release but potentiates mechanosensitive ATP release. Our study indicates a novel mechanism of mechanotransduction that would allow cells to regulate membrane trafficking and protein transport/secretion in response to mechanical loading.