Cells that appear to be dying do not always die. When the plasma membrane ruptures, a molecular machine called ESCRT-III can patch the breach, allowing the cell to survive what should have been a lethal event. A study published in Cell Regeneration now reports that this repair system is not left to run unchecked: a protein named Tollip, short for Toll-interacting protein, acts as a conserved negative regulator that restrains ESCRT-III-mediated membrane repair and, in doing so, shapes both cell recovery and inflammatory signaling.
The research team, led by Julia M. Ferrick, Xinan Meng, Suhong Xu and Yi-Nan Gong, set out to find proteins that gather on damaged plasma membranes and might control the repair process. They used SILAC mass spectrometry, a quantitative proteomics technique based on non-radioactive isotopic amino acid labeling, to compare membrane fractions from damaged and undamaged cells. In their model, RIPK3-2Fv-NIH3T3 cells treated with a B/B dimerizer undergo oligomerization of RIPK3, which phosphorylates MLKL and triggers plasma membrane damage, mimicking necroptosis. By isolating membrane fractions through repeated centrifugation, the researchers could detect which proteins became enriched on damaged membranes.
The screen worked as intended. Known damage-site translocators, including MLKL, ESCRT components such as CHMP4B, CHMP2A, VPS4A, VPS4B and TSG101, annexins, and the calcium-sensing conventional protein kinases C alpha and beta, all showed enrichment in the damaged membrane fraction. In contrast, proteins known not to translocate, such as RIPK3 itself and the novel or atypical PKCs lacking calcium-sensing C2 domains, were not enriched. Pathway analysis of the enriched proteins highlighted necroptosis, calcium binding and phospholipid binding among the overrepresented categories, giving the team a shortlist of candidate repair regulators.
Among the calcium-binding and C2-domain proteins, one candidate stood out: Tollip, whose C2 domain can bind both calcium and phospholipids. Although Tollip is not an official ESCRT component, it has been described as an alternative ESCRT-0 protein because it binds Tom1, a ubiquitin-binding protein linked to the ESCRT-0 machinery that initiates cargo sorting into the ESCRT pathway. Its exact role in ESCRT-III-mediated plasma membrane repair, however, had never been defined, making it a compelling target for follow-up experiments.
The researchers confirmed Tollip recruitment to damaged membranes in several ways. Western blotting showed that more Tollip accumulated in membrane fractions after sub-lethal damage was induced with B/B in engineered NIH3T3 cells, with digitonin in HT-29 cells, or with the TSZ cocktail that activates MLKL-mediated necroptosis. Live imaging of GFP-tagged Tollip revealed marked translocation to the plasma membrane after damage. Crucially, when the cells co-expressed CHMP4B-mCherry, a well-established marker of the precise damage site, GFP-Tollip co-translocated to the same locations, indicating that Tollip does not merely drift to the membrane but converges on the actual rupture sites.
The team also tested whether this recruitment is evolutionarily conserved. Using a needle-wound model in the epidermis of the roundworm Caenorhabditis elegans, where the Tollip homolog is called TLI-1, they observed that GFP-labeled TLI-1 accumulated at wound sites within minutes of injury. Moreover, TLI-1 and VPS-32.1, the worm counterpart of the ESCRT-III subunit CHMP4B, were recruited together and co-localized at the wound. Together, these imaging data established that Tollip translocation to membrane damage sites is a conserved feature across species.
Functionally, the picture that emerged was of a protein that restrains repair. The researchers generated Tollip-deficient cells in two ways: NIH3T3 lines carrying Tollip-targeting shRNA and HT-29 human cells carrying Tollip-targeting sgRNA. After sub-lethal digitonin treatment, Tollip-deficient HT-29 cells showed viability similar to controls at 24 hours, suggesting Tollip does not affect the initial damage phase, but by 48 hours they began to outperform controls, and in long-term clonogenic assays they formed significantly more colonies. The same held true in the NIH3T3 system with B/B or digitonin, and the phenotype was rescued by re-expressing an shRNA-resistant Tollip. Conversely, cells overexpressing Tollip formed fewer colonies, confirming that Tollip negatively regulates long-term cell survival after membrane damage.
The mechanism appears to run through ESCRT-III itself. Using CHMP2A, a core ESCRT-III component, as a readout of repair activity, western blot quantification showed that more CHMP2A translocated to the plasma membrane after damage in Tollip-deficient cells, while overexpression of Tollip suppressed this translocation. CHMP4B translocation was likewise reduced in Tollip-overexpressing cells. Intriguingly, Tollip’s own recruitment followed different rules: whereas ESCRT-III recruitment depends on calcium influx through membrane pores, Tollip translocated to damaged membranes even in calcium-free culture media, distinguishing its mode of action from that of the repair machinery it restrains. Domain mapping showed that the C2 domain was the most important contributor to Tollip translocation, and that a CUE-domain mutation that abolishes ubiquitin binding only partially rescued the Tollip-deficient phenotype, suggesting that Tollip may mask ubiquitin signals at damage sites to limit ESCRT-III assembly.
The findings also connect membrane repair to immunity. Sub-lethal plasma membrane ruptures trigger what the authors call the Plasma Membrane Integrity, or PMI, pathway: calcium influx recruits phosphorylated conventional PKCs to damage sites, activating the TAK1/IKK axis and the RelA/Cux1 transcriptional complex, which drives production of chemokines and cytokines including CXCL1, CXCL10, CXCL8 and LIF. In the new study, control cells responded to B/B-induced damage with robust transcriptional upregulation of Cxcl1, Cxcl10 and Lif, confirmed at the protein level by CXCL1 ELISA, whereas Tollip-deficient cells showed significantly reduced induction. The explanation follows from the repair kinetics: if ESCRT-III reseals pores too quickly, calcium influx and downstream signaling are cut short. By slowing repair, Tollip maintains the sub-lethal ruptures that fuel optimal PMI pathway output, positioning it as a molecular rheostat linking membrane damage repair to inflammatory signaling.
The authors are candid about the limits of the work. They could not establish ESCRT-III-deficient cells to test whether Tollip’s effects require the repair machinery, because ESCRT-III is essential for multiple cellular processes; CRISPR knockout attempts failed and transient knockdown left too few surviving cells for long-term assays. They also note that the molecular mechanism has not been demonstrated directly and that Tollip might influence ESCRT-III indirectly, although its known role as a parallel ubiquitin-binding adaptor to ESCRT-0 in cargo trafficking makes an ESCRT-independent action less likely. Even so, the study reframes plasma membrane repair as a finely tuned process rather than a simple rescue operation. In disease contexts where flatliner signaling has been observed, including hepatocarcinogenesis, mold allergen exposure and pneumolysin-producing bacterial infection, a protein that decides how long a damaged cell stays broken, and how loudly it calls for immune reinforcements, is likely to matter. Future work, the authors say, will explore Tollip’s immunomodulatory role in cancer, transplantation, type 2 immunity and bacterial infection models.
Subject of Research: The role of Tollip in regulating ESCRT-III-mediated plasma membrane repair and immune signaling
Article Title: Tollip antagonizes ESCRT-III-mediated plasma membrane repair and cell recovery
Article References: Ferrick, J. M., Meng, X., Morgan, E., Kalvi, A., Li, Z., Li, C., Chang, C.-Y., Xu, S., & Gong, Y.-N. (2026). Tollip antagonizes ESCRT-III-mediated plasma membrane repair and cell recovery. Cell Regeneration, 15(1), Article 17. https://doi.org/10.1186/s13619-026-00289-7
Image Credits: AI Generated
DOI: 10.1186/s13619-026-00289-7
Keywords: Tollip, ESCRT-III, plasma membrane repair, cell death, necroptosis, flatliner cells, PMI pathway, cytokines, C. elegans, proteomics, calcium signaling, ubiquitin
News Source: Gregory Coleman. (October 29, 2026). Scientists identify Tollip as a brake on plasma membrane repair. Scienmag.
