Biology subjects

Tan, J. X.

Publications and source records attributed to Tan, J. X..

5 recordsLinked to original sources

bioRxiv2026

SOLAR Mediates Lysosomal Membrane Repair and Redox Defense

Lysosomal damage is increasingly recognized as a hallmark of aging. Understanding lysosomal quality control may open new therapeutic strategies to enhance lysosomal resilience. Here, we identify SOLAR (SQSTM1/p62 Oligomer-mediated Lysosomal Antioxidant Defense And Membrane Repair), a lysosomal quality control pathway that links CASM (conjugation of ATG8 to single membranes) to p62-driven membrane repair and redox signaling. In this pathway, CASM, but not macroautophagy, recruited p62 to damaged lysosomes. Efficient lysosomal recruitment of p62 required its ATG8-binding and self-oligomerizing domains, enabling p62 assemblies to promote membrane repair. p62 mutations associated with neurodegeneration interfered with p62 recruitment and compromised lysosomal repair. Besides membrane repair, the SOLAR pathway also activated the p62-KEAP1-NRF2 redox signaling axis, driving transcriptional upregulation of antioxidative genes and cholesterol biosynthesis. By integrating membrane repair and redox defense, SOLAR establishes a coordinated lysosomal quality control pathway with implications for aging and degenerative disease.

cell biology↗

bioRxiv2025

PtdIns(3,5)P2 Is an Endogenous Ligand of STING in Innate Immune Signaling

Cytosolic DNA exposure triggers innate immune responses through cyclic GMP-AMP (cGAMP) synthase (cGAS)1-3. Upon binding to DNA, cGAS is activated to produce cGAMP, which functions as a second messenger that binds to stimulator of interferon genes (STING), an endoplasmic reticulum (ER)-localized signaling adaptor3-5. STING then traffics from the ER to the Golgi, leading to activation of the kinases TBK1 and IKK and subsequent induction of interferons and other cytokines6-10. Here we show that phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P2] is an endogenous ligand of STING that functions together with cGAMP to induce STING activation. Proteomics analysis identified a constitutive interaction between STING and PIKfyve, an enzyme that produces PtdIns(3,5)P2 in mammalian cells. Deletion of PIKfyve blocked STING trafficking from the ER and TBK1 activation. In vitro reconstitution revealed a strong and selective effect of PtdIns(3,5)P2 on STING activation. Purified STING bound directly to PtdIns(3,5)P2 in a fluorescence resonance energy transfer (FRET) assay. Consistently, PtdIns(3,5)P2 promoted cGAMP-induced STING oligomerization by binding to a groove between STING dimers as revealed by cryo-EM (Li et al., co-submitted). Similar to PIKfyve depletion, mutation of the PtdIns(3,5)P2-binding residues in STING blocked its trafficking and downstream signaling. These results reveal PtdIns(3,5)P2 as a lipid ligand of STING with essential roles in innate immunity.

biochemistry↗

bioRxiv2025

Regulation of STING activation by phosphoinositide and cholesterol

Stimulator of interferon genes (STING) is an essential adaptor in the cytosolic DNA sensing innate immune pathway. STING is activated by cyclic-GMP-AMP (cGAMP) produced by the DNA sensor cGAMP synthase (cGAS). cGAMP-induced high-order oligomerization and translocation of STING from the endoplasmic reticulum to Golgi and post-Golgi vesicles are critical for STING activation. Recent studies have shown that phosphatidylinositol phosphates (PIPs) and cholesterol also play important roles in STING activation, but the underlying mechanisms remain unclear. Here, we demonstrate that cGAMP-induced high-order oligomerization of STING is enhanced strongly by PI(3,5)P2 and PI(4,5)P2, and by PI(4)P to a less extent. Our cryo-EM structures reveal that PIPs together with cholesterol bind at the interface between STING dimers, directly promoting the high-order oligomerization. The structures also provide an explanation for the preference of the STING oligomer to different PIPs. Mutational and biochemical analyses confirm the binding modes of PIPs and cholesterol and their roles in STING activation. Our findings shed light on the regulatory mechanisms of STING by specific lipids, which may underlie the role of intracellular compartment trafficking in dictating STING signaling.

immunology↗

bioRxiv2023

A conserved ion channel function of STING mediates non-canonical autophagy and cell death

The cGAS/STING pathway triggers inflammation in response to diverse cellular stresses such as infection, cellular damage, senescence, normal aging, and age-related disease. Besides inflammation, STING also triggers non-canonical autophagy and cell death, the former of which requires the proton pump V-ATPase- mediated LC3 lipidation to single membrane STING vesicles. V-ATPase is known to sense organelle de- acidification in other contexts and recruits the ATG16L1 complex for direct conjugation of LC3/ATG8 to single membranes (CASM). However, it is unclear how STING activates V-ATPase for non-canonical autophagy. Here we report that upon STING activation, the transmembrane domain (TMD) of STING significantly reorganizes and forms an electron-sparse pore in the center. Cellular imaging and in vitro ion flux assays revealed that STING is critical for proton efflux and pH neutralization of Golgi-derived STING vesicles. A chemical ligand of STING, C53, which binds to and blocks the channel of STING strongly inhibited STING-mediated proton flux in vitro and vesicular de-acidification in cells. C53 also abolished STING-dependent LC3 lipidation and cell death. Thus, the ion channel function of STING activates non-canonical autophagy and cell death through vesicle de-acidification.

biochemistry↗

bioRxiv2020

Prediction of novel components of bacterial ribosomes by crowd-sourced analysis of RNA sequencing data

Bacterial resistance to antibiotics is a growing problem that is projected to cause more deaths than cancer in 2050. Consequently, novel antibiotics are urgently needed. Since more than half of the available antibiotics target the bacterial ribosomes, proteins that are involved in protein synthesis are thus prime targets for the development of novel antibiotics. However, experimental identification of these potential antibiotic target proteins can be labor-intensive and challenging, as these proteins are likely to be poorly characterized and specific to few bacteria. In order to identify these novel proteins, we established a Large-Scale Transcriptomic Analysis Pipeline in Crowd (LSTrAP-Crowd), where 285 individuals processed 26 terabytes of RNA-sequencing data of the 17 most notorious bacterial pathogens. In total, the crowd processed 26,269 RNA-seq experiments and used the data to construct gene co-expression networks, which were used to identify more than a hundred uncharacterized genes that were transcriptionally associated with protein synthesis. We provide the identity of these genes together with the processed gene expression data. The data can be used to identify other vulnerabilities or bacteria, while our approach demonstrates how the processing of gene expression data can be easily crowdsourced.

bioinformatics↗