MODULATION OF ATP-GATED NONSELECTIVE CATION CHANNEL (P2X(1) RECEPTOR)ACTIVATION AND DESENSITIZATION BY THE ACTIN CYTOSKELETON

1. ATP-gated non-selective cation channels from the rat vas deferens ( P2X(1) receptors) were stably expressed in HEK 293 cells, assayed by p atch clamp on the first day after passage of the culture, and found to have whole-cell current kinetics markedly faster in both activation a nd desensitization than those found in the native vas deferens tissue, in agreement with previous reports. 2. By the second day after passag e of the culture, however, the whole-cell current kinetics of the expr essed receptors shifted, slowing in both activation and desensitizatio n. The kinetic change correlated with a change in phenotype of the hos t cells from round to flat, and the slower kinetics were similar to na tive P2X(1) currents recorded from dissociated rat vas deferens smooth muscle cells. Two point mutations in a pore-like domain near or withi n the second transmembrane domain of the P2X(1) receptor appeared to c onfer on the receptor the inability to effect this change in kinetics over time. 3. Treatment of cells on day 3 after passage with cytochala sins B or D caused a reversion to the rapid kinetics phenotype, implic ating the actin cytoskeleton in the development of the native kinetics . P2X(1) receptors may therefore require interaction with an intact ac tin cytoskeleton for native kinetics, and the mutants may be defective either in interaction with the actin skeleton or in coupling the inte raction to gating.