P2X reseptörlerinin aktive ettiği membran geçirgenliğinde seçiciliğinin, tür farklarının ve gedik-kavşak proteinlerinin rolünün incelenmesi

Abstract

P2X7 is one of the seven members of P2X receptor family which is permeable to small cations. It activates a permeablity to large molecules up to 800 Da and in this respect differs from other P2X receptors. This property of P2X7 receptors has been a subject of many investigations. It is showed that this increase in permeability is selective and the selectivity depends on the cell type. It is claimed that this permeability occurs via a gap-junction protein called pannexin-1. Pannexin-1 is a membrane protein and permeable to large molecules up to 1 kDa. It is activated by increase in intracellular [Ca2+]i, membrane depolarization, and mechanical stress. In this thesis, RAW 264.7 cells and HEK-mP2X7 cells expressing P2X7 receptor cloned from RAW 264.7 cells were used. This method were thought to test whether the permeability response endogenously activated by ATP in RAW 264.7 cells occurs via P2X7 or not and to test whether P2X7 receptor is sufficient to large permeability or not. Firstly, a permeability difference has been seen between these cells. RAW 264.7 cells uptake both positively charged YO-PRO-1 and negatively charged Lucifer Yellow. HEK-mP2X7 cells uptake only positively charged YO-PRO-1. Secondly, agonist potency differences between cells have been found. Therefore, P2X7 receptor per se is not sufficient to uptake Lucifer Yellow and it needs an accessory protein. On the other hand, inhibitors of pannexin-1 and anion transporters clearly enhanced Lucifer Yellow uptake at concentrations that they did not effect YO-PRO-1 uptake. Insufficiency of receptor expression to activate Lucifer Yellow permeability and differential effects of inhibitors on permeability pathways showed that Lucifer Yellow and YO-PRO-1 uptake were different permeability pathways.