Activation and Desensitization of the Recombinant P2X1 Receptor at Nanomolar ATP Concentrations

Activation and desensitization kinetics of the rat P2X1 receptor at nanomolar ATP concentrations were studied in Xenopus oocytes using two-electrode voltage-clamp recording. The solution exchange system used allowed complete and reproducible solution exchange in <0.5 s. Sustained exposure to 1–100 nM ATP led to a profound desensitization of P2X1 receptors. At steady-state, desensitization could be described by the Hill equation with a K1/2 value of 3.2 ± 0.1 nM. Also, the ATP dependence of peak currents could be described by a Hill equation with an EC50 value of 0.7 μM. Accordingly, ATP dose-effect relationships of activation and desensitization practically do not overlap. Recovery from desensitization could be described by a monoexponential function with the time-constant τ = 11.6 ±1.0 min. Current transients at 10–100 nM ATP, which elicited 0.1–8.5% of the maximum response, were compatible with a linear three-state model, C-O-D (closed-open-desensitized), with an ATP concentration-dependent activation rate and an ATP concentration-independent (constant) desensitization rate. In the range of 18–300 nM ATP, the total areas under the elicited current transients were equal, suggesting that P2X1 receptor desensitization occurs exclusively via the open conformation. Hence, our results are compatible with a model, according to which P2X1 receptor activation and desensitization follow the same reaction pathway, i.e., without significant C to D transition. We assume that the K1/2 of 3.2 nM for receptor desensitization reflects the nanomolar ATP affinity of the receptor found by others in agonist binding experiments. The high EC50 value of 0.7 μM for receptor activation is a consequence of fast desensitization combined with nonsteady-state conditions during recording of peak currents, which are the basis of the dose-response curve. Our results imply that nanomolar extracellular ATP concentrations can obscure P2X1 receptor responses by driving a significant fraction of the receptor pool into a long-lasting refractory closed state

Heterogeneous Graph-based Trajectory Prediction using Local Map Context and Social Interactions

Precisely predicting the future trajectories of surrounding traffic participants is a crucial but challenging problem in autonomous driving, due to complex interactions between traffic agents, map context and traffic rules. Vector-based approaches have recently shown to achieve among the best performances on trajectory prediction benchmarks. These methods model simple interactions between traffic agents but don't distinguish between relation-type and attributes like their distance along the road. Furthermore, they represent lanes only by sequences of vectors representing center lines and ignore context information like lane dividers and other road elements. We present a novel approach for vector-based trajectory prediction that addresses these shortcomings by leveraging three crucial sources of information: First, we model interactions between traffic agents by a semantic scene graph, that accounts for the nature and important features of their relation. Second, we extract agent-centric image-based map features to model the local map context. Finally, we generate anchor paths to enforce the policy in multi-modal prediction to permitted trajectories only. Each of these three enhancements shows advantages over the baseline model HoliGraph.Comment: Accepted on IEEE ITSC 202

Проектирование комплекса геофизических исследований скважин для определения коллекторских свойств на Яунлорском месторождении (ХМАО-Югра)

Объектом исследования является проектная скважина №7200 глубиной 3100 м со вскрытием юрских отложений – пласты ЮС1, ЮС2, ЮС3. Скважина заложена в пределах Яунлорского куполовидного поднятия. Цель работы: проектирование комплекса геофизических исследований в открытом стволе скважины №1400 для оценки коллекторских свойств пластов-коллекторов в среднеюрском нефтегазоносном комплексе на Яунлорском месторождении.The object of the study is project well No. 7200 with a depth of 3100 m with the discovery of Jurassic deposits - formations J1, J2, J3. The well is within the domed uplift of Jaunlor. Purpose of work: designing a complex of geophysical surveys in an open well of well No. 1400 for assessing the reservoir properties of the formation in the middle Jurassic of the oil and gas complex at the Yaunlor field

Roles of individual N-glycans for ATP potency and expression of the rat P2X1 receptor

P2X1 receptor subunits assemble in the ER of Xenopus oocytes to homotrimers that appear as ATP-gated cation channels at the cell surface. Here we address the extent to which N-glycosylation contributes to assembly, surface appearance, and ligand recognition of P2X1receptors. SDS-polyacrylamide gel electrophoresis (PAGE) analysis of glycan minus mutants carrying Gln instead of Asn at five individual NXT/S sequons reveals that Asn284 remains unused because of a proline in the +4 position. The four other sites (Asn153, Asn184, Asn210, and Asn300) carryN-glycans, but solely Asn300 located only eight residues upstream of the predicted reentry loop of P2X1acquires complex-type carbohydrates. Like parent P2X1, glycan minus mutants migrate as homotrimers when resolved by blue native PAGE. Recording of ATP-gated currents reveals that elimination of Asn153 or Asn210 diminishes or increases functional expression levels, respectively. In addition, elimination of Asn210 causes a 3-fold reduction of the potency for ATP. If three or all four N-glycosylation sites are simultaneously eliminated, formation of P2X1 receptors is severely impaired or abolished, respectively. We conclude that at least oneN-glycan per subunit of either position is absolutely required for the formation of P2X1 receptors and that individual N-glycans possess marked positional effects on expression levels (Asn154, Asn210) and ATP potency (Asn210)

The P2X(6) subunit, unlike all other P2X isoforms, is incapable of forming homotrimer receptors

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Aminoglycoside block of P2X2 receptors heterologously expressed in Xenopus laevis oocytes

Aminoglycosides are polycationic antibiotics that have been shown to block a variety of cation channels. The inhibitory effect of externally applied aminoglycosides on P2X2 receptor currents was examined after heterologous expression in Xenopus laevis oocytes using the two-electrode voltage-clamp technique. All of the aminoglycosides tested inhibited the ATP-evoked responses with potencies ranging from 71 μM to 2 mM (IC50 values). The ranked order of potency was streptomycin > gentamicin > neomycin > paromomycin > kanamycin. The inhibition of P2X receptor currents was independent of the ATP concentration used for the activation, which is compatible with a noncompetitive mechanism. The inhibition was voltage-dependent and was reduced at more positive membrane potentials. To examine whether the current block was dependent on the receptor conformation, the aminoglycoside effect on a non-desensitizing P2X2-X1 receptor chimera was analyzed. The results from these measurements suggest that inhibition is caused by an open pore block that locks the P2X receptor chimera in an open nonconducting state from which the agonist dissociation is slow. We also demonstrate that the P2X2-X1 chimera can serve as a tool to directly test whether an antagonist acts competitively or not