https://opendata.uni-halle.de//handle/1981185920/32199 2026-04-04T06:43:35Z https://opendata.uni-halle.de//handle/1981185920/120639 Title: Activation of the P2X7 receptor by functionally different ATP activation sites Author(s): Markwardt, Fritz; Berthold, Malte; Hawro Yakoob, Sanaria; Schmalzing, Günther Abstract: The homotrimeric P2X7 receptor (P2X7R) contains three ATP4- binding sites in its ectodomain. Here, we investigated the role of the individual ATP4- activation sites of the rat P2X7R (rP2X7R) using trimeric rP2X7R concatamers consisting either of three wild-type subunits (7-7-7) or concatamers with up to three subunits having knocked-out ATP binding sites (7ko-7ko-7ko). Following expression in Xenopus oocytes, ATP4--elicited ion currents were recorded using the two-microelectrode voltage clamp technique. The 7-7-7 concatamer exhibited a biphasic ATP4- concentration dependence, best fit by the sum of two Hill functions, confirming the existence of functionally distinct ATP4- activation sites. The activation time course of the 7-7-7 was best approximated by the sum of a fast and a slow exponential saturating activation component. Similarly, deactivation exhibited both a fast and a slow exponential decay. Only one Hill function was required to best fit the ATP4- concentration dependence of concatamers with only two or one ATP4- binding sites, and their deactivation time courses largely lacked the slowly deactivating components. We conclude that binding of one ATP4- is sufficient for partial activation of the rP2X7R and that allosteric effects occur when all three ATP4- binding sites are occupied, leading to distinct functional activation sites. 2025-01-01T00:00:00Z https://opendata.uni-halle.de//handle/1981185920/103158.3 Title: Permeation characteristics of hP2X7 Author(s): Markwardt, Fritz; Berthold, Malte 2024-06-01T00:00:00Z https://opendata.uni-halle.de//handle/1981185920/66415 Title: Effect of dihydropyridines on the full-length human P2X5 receptor Author(s): Schiller, Ida C.; Markwardt, Fritz Abstract: The P2X5 receptor, an ATP-gated cation channel, is believed to be involved in tumor development, inflammatory bone loss and inflammasome activation after bacterial infection. Therefore, it is a worthwhile pharmacological target to treat the corresponding diseases. Here, we investigated the effects of dihydropyridines on the human full length P2X5 receptor (hP2X5FL) heterologously expressed in Xenopus oocytes using the two-microelectrode voltage clamp method. Agonist dependency, kinetics and permeation behavior were similar to hP2X5FL expressed in HEK293 or 1321N1 cells. Of 7 commercially available and 4 newly synthesized dihydropyridines tested, only amlodipine exerted an inhibitory effect, but only at a high concentration of 300 µM. Isradipine and even more nimodipine stimulated ATP-induced currents in the low micromolar range. We conclude that dihydropyridines are not suited as antagonistic agents on hP2X5, but that a side effect of nimodipine therapy could be a stimulatory effect on inflammatory processes. 2022-01-01T00:00:00Z https://opendata.uni-halle.de//handle/1981185920/34676 Title: Dissection of P2X4 and P2X7 receptor current components in BV-2 microglia Author(s): Markwardt, Fritz 2020-01-01T00:00:00Z