Cryo-EM Reveals How ATP Switches Off the Human NLRP6 Inflammasome

The innate immune system is built on a paradox: the same molecular machinery that defends the body against infection can, when mishandled, turn that defense against the body itself. Few proteins embody this tension as vividly as NLRP6, a human pattern-recognition receptor that assembles into large signaling complexes known as inflammasomes. When NLRP6 is activated, it nucleates the assembly of filaments that ultimately drive inflammatory signaling and defensive cell death. When it is misregulated, the consequences can include chronic inflammation and disrupted barrier function in the intestine. A new study published in Nature Structural & Molecular Biology by Sheng Cui and colleagues now provides the most direct structural picture to date of how the cell keeps this dangerous machine in check, showing in atomic detail how adenosine triphosphate, better known as ATP, acts as an endogenous inhibitor of human NLRP6.

The central achievement of the work is the determination of cryo-electron microscopy structures of human NLRP6 in two distinct conformational states: one in which ATP is bound within the nucleotide-binding domain, and one in which that domain is unoccupied. Capturing a signaling protein of this complexity in more than one state is a technical tour de force. NLRP6 belongs to the NOD-like receptor family, whose members are built from a modular architecture that includes a pyrin domain for downstream signaling, a central nucleotide-binding oligomerization domain, or NBD, and a leucine-rich repeat region that is thought to sense activating cues. In the resting state, these modules are folded against one another in a self-suppressed arrangement; upon activation, the protein must rearrange dramatically to oligomerize and recruit downstream adaptors. Cryo-EM is uniquely suited to visualizing both the compact monomeric states and the extended oligomeric assemblies that NLR-family proteins adopt along this trajectory.

What the structures reveal is that ATP is not merely a passive occupant of the nucleotide-binding pocket but an active participant in the regulatory logic of the receptor. By binding within the NBD, ATP stabilizes a conformation of NLRP6 in which the domains are locked together in an arrangement that precludes the transitions required for inflammasome assembly. In effect, the nucleotide acts as a molecular latch. The comparison between the ATP-bound and ATP-unbound conformations allowed the researchers to trace precisely which intramolecular contacts shift when the nucleotide engages the pocket, and how those shifts propagate through the protein to restrain the regions that would otherwise mediate self-association and filament formation.

This finding carries considerable conceptual weight because nucleotide binding has historically been viewed primarily through the lens of activation in this protein family. Many NLR proteins require ATP binding or hydrolysis for their oligomerization and signaling functions, and ATP or its analogues have often been used experimentally to promote the assembly of inflammasome complexes in vitro. The new structures of NLRP6 invert that expectation for this particular receptor, identifying ATP as a stabilizer of the inactive, monomeric state rather than a driver of oligomerization. The work thus adds an important nuance to the general model of NLR regulation: the effect of nucleotide binding is not uniform across the family, and it must be understood receptor by receptor, in structural terms, rather than assumed.

The mechanistic detail extracted from the structures is substantial. By comparing the two conformational states at high resolution, Cui and colleagues could identify the specific structural elements that respond to ATP occupancy. These include regions of the NBD that reposition relative to the adjacent regulatory domains, contacts that either form or dissolve depending on whether the nucleotide is present, and hinge-like segments whose mobility governs whether the protein can escape its autoinhibited fold. Such residue-level information is precisely what is needed to design targeted experiments, and indeed the study is framed around structure-guided biochemical validation of the observed interactions, a standard that has become the norm for mechanistic structural biology of innate immune receptors.

The broader context of this work is the intense interest in the NLRP family of inflammasome sensors, and in NLRP3 in particular, as drug targets. Overactive inflammasome signaling has been implicated in a wide range of human diseases, from gout and atherosclerosis to neurodegeneration and inflammatory bowel disease. NLRP6, which is especially prominent in epithelial tissues such as the intestine, has emerged as a key regulator of mucosal immunity and of the interplay between the host and the microbiome. Understanding how NLRP6 is held in its inactive state therefore has implications that extend well beyond basic receptor biology, touching on the architecture of the intestinal barrier and the maintenance of a healthy relationship with the microbial communities that inhabit it.

From a structural biology standpoint, the study also exemplifies the current maturity of cryo-electron microscopy as a method for dissecting regulatory mechanisms in immune proteins. A decade ago, obtaining structures of a large, flexible, multidomain receptor in even one state would have been a career-defining effort. Today, as this work demonstrates, it is feasible to capture the same protein in multiple functional states and to compare them directly, transforming what was once a static portrait of a protein into something closer to a molecular film. The two NLRP6 structures together form precisely such a comparison: one frame showing the nucleotide-engaged, inhibited receptor, another showing the conformation from which activation must proceed.

The identification of ATP as an endogenous inhibitor also raises intriguing questions about how intracellular nucleotide levels tune inflammasome sensitivity. Cells experience fluctuations in ATP availability under stress, during metabolic shifts, and in the course of infection. If ATP occupancy of the NLRP6 nucleotide pocket keeps the receptor in a signaling-competent-off state, then changes in cellular energy status could, in principle, translate into changes in the threshold at which NLRP6 fires. Whether such metabolic regulation operates in living cells, and how it intersects with the other inputs that NLRP6 senses, are questions that the structural work now makes experimentally accessible. The structures provide a concrete physical hypothesis that cell biological and biochemical studies can test directly.

For the growing community of researchers attempting to develop inflammasome-directed therapeutics, the study offers a template. Drugs that stabilize an autoinhibited conformation, or that mimic the effect of ATP binding, could in principle dampen pathological NLRP6 signaling. Conversely, understanding exactly which interactions must break for activation to occur points to where small molecules might lock the receptor open, should augmentation of NLRP6-dependent immunity ever be clinically desirable. The structural map produced by Cui and colleagues converts those goals from abstract ambitions into chemically addressable problems, listing the pockets, interfaces, and conformational switches that any future drug would need to engage. In a field where the therapeutic stakes are high and the molecular targets are notoriously difficult to control, that kind of precision is exactly what progress looks like.

Subject of Research: Structural mechanism of ATP-mediated inhibition of the human NLRP6 inflammasome revealed by cryo-electron microscopy.

Article Title: Structural mechanisms for ATP-mediated inhibition of human NLRP6 inflammasome

Article References: Cui, Z., Sheng, Q., Son, M., Goo, Y. A., & Shen, C. (2026). Structural mechanisms for ATP-mediated inhibition of human NLRP6 inflammasome. Nature Structural & Molecular Biology. https://doi.org/10.1038/s41594-026-01878-5

Image Credits: AI Generated

DOI: 10.1038/s41594-026-01878-5

Keywords: NLRP6, inflammasome, ATP, cryo-EM, innate immunity, NOD-like receptors, structural biology, inflammation, NBD, immune regulation, intestinal immunity, autoinhibition