P2X purinergic receptors, the fast sensor of ATP

MOFFAT LUCIANO

Salto

Congreso; Latin American Crosstalk in Biophysics and Physiology; 2015

Sociedad Argentina de Biofísca. Seccional Biofísica de la Sociedad Uruguaya de Ciencias

P2Xreceptors are trimeric ion channels that gate after binding ATPmolecules. They are located at the extracellular side of the cellularmembrane of most vertebrate tissues. Within purinergic signalling, P2Xreceptors are the fastest sensors. To fully understand the ATP- sensingabilities of this receptors, experiments where carried out on excised outpatches containing recombinant rat P2X2 receptors. Those patches could bepositioned close to a stable interface between two solutions one containingATP and the other not. By optimizing the control of a switching deviceactuated by a piezo it was possible to expose the excised patch to ATP forcarefully controlled periods of time, from the hundreds of microseconds tothe tens of seconds range. Patch clamp amplifiers allow to measure thedynamic response of the conductance of the P2X2 receptors to those pulsesand this response was compared to the response predicted by several kineticmodels. An allosteric kinetic model that assumed three conformationalchanges: ATP-binding, gate opening and either channel or subunit flippingwas able to reproduce the experimental results to 0.2ms 1 pulses of 0.2 -10mM ATP. In this talk I will show a reinterpretation of those experiments onthe light of new structural information of P2X4. A deep understanding ofthe kinetic properties of puringergic receptors is key to properly model thewhole purinergic signaling pathway. The results presented suggest that it ispossible to mathematically reproduce the temporal dynamics of thisreceptors on carefully controlled conditions. With help of Bayesianstatistics 2 it might be possible to adjust these models to predict the behaviorof P2X receptors on uncontrolled, physiological, conditions