PtdIns(3,5)P2 is an endogenous ligand of STING in innate immune signalling
Article meta
- Article Date: 04 February 2026
- Article URL: https://www.nature.com/articles/s41586-025-10084-0
- Article Title: PtdIns(3,5)P2 is an endogenous ligand of STING in innate immune signalling
- Article Image: (not provided)
Summary
This Nature paper identifies phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2, aka PI(3,5)P2) as an endogenous lipid ligand that binds STING and promotes its signalling activity. Using biochemical, genetic and cell-biological approaches the authors show PIKfyve-generated PI(3,5)P2 binds to STING, potentiates cGAMP-driven TBK1 trans-autophosphorylation and supports both canonical (type I interferon) and noncanonical (TFEB activation, LC3 lipidation/autophagy) STING outputs.
The work combines mass spectrometry (identifying TBK1 and ACBD3 among STING interactors), CRISPR and inhibitor studies (PIKfyve depletion and the inhibitor YM201636), liposome reconstitution assays showing that adding diC8 PI(3,5)P2 enhances cGAMP-stimulated STING–TBK1 activation, and mutational analysis (notably a K20A/R71A STING mutant) that disrupts PI(3,5)P2 binding and blocks downstream responses. The data separate STING trafficking through the Golgi from the lipid-dependent activation step and implicate PI4KB as an additional phosphoinositide regulator of STING signalling.
Key Points
- PtdIns(3,5)P2 (PI(3,5)P2) is reported as an endogenous ligand for STING that enhances its signalling when cGAMP is present.
- PI(3,5)P2 is synthesised by PIKfyve; both genetic depletion and pharmacological inhibition (YM201636) of PIKfyve suppress STING-mediated TBK1 phosphorylation and downstream gene induction.
- In vitro liposome reconstitution shows diC8 PI(3,5)P2 promotes cGAMP-dependent TBK1 and STING phosphorylation — consistent with a direct lipid effect on the STING complex.
- STING contains basic residues in its N-terminus/cytosolic loop required for PI(3,5)P2 binding; the K20A/R71A mutant fails to respond to the lipid and has defects in both interferon signalling and noncanonical outputs (TFEB activation, LC3 lipidation).
- PI(3,5)P2 supports TBK1 trans-autophosphorylation rather than altering TBK1 recruitment to STING-containing membranes.
- Mass spectrometry and imaging identify TBK1 and ACBD3 as STING interactors and place STING trafficking through the Golgi/TGN as part of the activation route, with PI4KB also influencing the process.
- Pharmacological inhibition of PIKfyve can uncouple STING trafficking from productive signalling — a potentially important caveat for therapeutics targeting endomembrane lipids.
Content summary
The authors combine cellular, biochemical and structural-probing experiments to argue that PI(3,5)P2 is a physiologically relevant regulator of STING. They show PIKfyve associates with STING and that inhibiting PIKfyve or depleting it reduces cGAMP-stimulated TBK1 phosphorylation and interferon-stimulated gene expression. Importantly, liposome-based reconstitution demonstrates that adding PI(3,5)P2 into the membrane environment potentiates STING-dependent TBK1 activation, indicating a direct regulatory role for the lipid.
Mutational analysis identifies STING residues required for PI(3,5)P2 binding; a binding-defective STING mutant cannot support TFEB activation or autophagy-linked LC3 lipidation. Imaging and co-immunoprecipitation data place STING trafficking through Golgi/TGN compartments and reveal interacting partners (ACBD3, TBK1). Parallel inhibition of PI4KB also reduces STING signalling, suggesting multiple Golgi phosphoinositides contribute to full STING activation.
Context and relevance
This study shifts the conceptual model of STING activation by adding a lipid-ligand layer: beyond cyclic dinucleotide binding, STING activity is tuned by local phosphoinositide composition at ER–Golgi/TGN compartments. That matters because STING is central to antiviral defence, tumour immunity and autophagy/lysosomal homeostasis. Identifying PI(3,5)P2 as a regulator clarifies how membrane identity and lipid kinases (PIKfyve, PI4KB) integrate with STING’s protein partners (TBK1, ACBD3) to produce specific downstream outcomes.
There are practical implications: PIKfyve inhibitors or modulators of Golgi phosphoinositides might blunt or reshape STING-driven immunity — relevant for both drug discovery (STING agonists/antagonists, cancer immunotherapy, antiviral strategies) and for interpreting phenotypes of compounds that perturb endosomal/lysosomal lipids. The finding also helps explain links between STING, lysosome biology and autophagy described in recent literature.
Why should I read this?
Short version: if you care about innate immunity, STING-targeted therapies or how membrane lipids control signalling, this paper hands you a new piece of the puzzle. It’s the sort of discovery that changes how you think about where and when STING actually fires off downstream responses — and it flags lipid kinases as druggable levers. We read the heavy stuff so you don’t have to.
Author style
Punchy: this is a high-impact mechanistic advance. The authors use complementary in vivo, in vitro and genetic tools to make a clear causal case that PI(3,5)P2 binds and regulates STING. For scientists working on cGAS–STING biology, host defence, autophagy or membrane lipids, the study is highly relevant and worth close reading for experimental detail and assay approaches (notably the liposome reconstitution and binding assays).