Calhm2 has an important role in microglial activation and contributes to Alzheimer’s disease pathology.

Significance: Allosteric regulation, produced by the binding of a ligand at an allosteric site topographically distinct from the orthosteric site, represents a direct and efficient means for modulation of biological macromolecule function. Because allosteric modulators have advantages over classic orthosteric ligands as therapeutic agents, understanding the mechanism underlying allosteric modulation may open new therapeutic avenues. Here, we focused on allosteric regulation of P2X receptors, which are implicated in diverse pathophysiological processes, such as blood clotting, pain sensation, inflammation, and rheumatoid arthritis. Combining structural determination, molecular modeling, and mutagenesis, we identified a druggable allosteric site on P2X3. Our findings will facilitate the development of novel therapeutics targeting these receptors.

P2X receptors are non-selective cation channels gated by extracellular ATP, and the P2X7 receptor subtype plays a crucial role in the immune and nervous systems. Altered expression and dysfunctions of P2X7 receptors caused by genetic deletions, mutations, and polymorphic variations have been linked to various diseases, such as rheumatoid arthritis and hypertension. Despite the availability of crystal structures of P2X receptors, the mechanism of competitive antagonist action for P2X receptors remains controversial. Here, we determine the crystal structure of the chicken P2X7 receptor in complex with the competitive P2X antagonist, TNP-ATP. The structure reveals an expanded, incompletely activated conformation of the channel, and identified the unique recognition manner of TNP-ATP, which is distinct from that observed in the previously determined human P2X3 receptor structure. A structure-based computational analysis furnishes mechanistic insights into the TNP-ATP-dependent inhibition. Our work provides structural insights into the functional mechanism of the P2X competitive antagonist.

The acid-sensing ion channel 1 (ASIC1) is a key receptor for extracellular protons. Although numerous structural and functional studies have been performed on this channel, the structural dynamics underlying the gating mechanism remains unknown. We used normal mode analysis, mutagenesis, and electrophysiological methods to explore the relationship between the inherent dynamics of ASIC1 and its gating mechanism. Here we show that a series of collective motions among the domains and subdomains of ASIC1 correlate with its acid-sensing function. The normal mode analysis result reveals that the intrinsic rotation of the extracellular domain and the collective motions between the thumb and finger induced by proton binding drive the receptor to experience a deformation from the extracellular domain to the transmembrane domain, triggering the channel pore to undergo “twist-to-open” motions. The movements in the transmembrane domain indicate that the likely position of the channel gate is around Leu440. These motion modes are compatible with a wide body of our complementary mutations and electrophysiological data. This study provides the dynamic fundamentals of ASIC1 gating. The acid-sensing ion channels (ASICs) are key receptors for extracellular protons and are becoming increasingly important drug targets. However, their gating mechanism is still not fully understood. The crystallographic structure of the ASIC1 protein provides a clue, but the dynamics of the channel remains to be elucidated. Using computational biology, site-directed mutagenesis, and electrophysiological recordings, we investigated the dynamics of ASIC1 gating. Through “normal mode analysis,” we detected a series of collective motions between the beta turn and transmembrane domain, and between the thumb and finger domains, suggesting a deformation pathway related to channel gating. The intrinsic rotation of the extracellular domain and the collective motions between the thumb and finger domains that are induced by proton binding serve to deform the channel from the extracellular to the transmembrane domain, triggering a “twist-to-open” motion of the channel pore. The relationship between the dynamics and the gating mechanism was experimentally confirmed by a series of complementary mutations in ASIC1 and electrophysiological measurements. Our study also indicated that the likely position of the channel gate is around Leu440 within the ASIC1 protein. We propose a clear model correlating the structural dynamics of ASIC1 and its gating mechanism.

How particular bone marrow niche factors contribute to the leukemogenic activities of leukemia-initiating cells (LICs) remains largely unknown. Here, we showed that ATP levels were markedly increased in the bone marrow niches of mice with acute myeloid leukemia (AML), and LICs preferentially localized to the endosteal niche with relatively high ATP levels, as indicated by a sensitive ATP indicator. ATP could efficiently induce the influx of ions into LICs in an MLL-AF9–induced murine AML model via the ligand-gated ion channel P2X7. P2x7 deletion led to notably impaired homing and self-renewal capacities of LICs and contributed to an approximately 5-fold decrease in the number of functional LICs but had no effect on normal hematopoiesis. ATP/P2X7 signaling enhanced the calcium flux–mediated phosphorylation of CREB, which further transactivated phosphoglycerate dehydrogenase (Phgdh) expression to maintain serine metabolism and LIC fates. P2X7 knockdown resulted in a markedly extended survival of recipients transplanted with either human AML cell lines or primary leukemia cells. Blockade of ATP/P2X7 signaling could efficiently inhibit leukemogenesis. Here, we provide a perspective for understanding how ATP/P2X7 signaling sustains LIC activities, which may benefit the development of specific strategies for targeting LICs or other types of cancer stem cells.