Saturday, May 17, 2025
5/17/2025
Regulation of TLR trafficking for proper self versus non-self discrimination - PROJECT SUMMARY Inappropriate recognition of self nucleic acids (NA) by members of the Toll-like receptor (TLR) family can result in autoimmune diseases such as lupus and psoriasis. TLR7 (and TLR8 in humans) and TLR9 can be activated by self RNA and DNA, respectively, so defining the mechanisms that limit responses by these TLRs is highly relevant to human health and disease. There is also accumulating evidence that the mechanisms controlling TLR7 and TLR9 responses are distinct, but our understanding of the molecular bases for these differences and their relevance for disease remain poor. This application is a renewal of the grant that has funded our research studying the regulation of NA-sensing TLRs for 15 years. Our prior work helped to establish the paradigm that multiple mechanisms operate to restrict the function of NA-sensing TLRs to endosomes, which limits recognition of self NAs released from dead cells into the extracellular space. In the last funding period, we made a major breakthrough that revealed a new mechanism mediated by the TLR chaperone Unc93b1 that limits TLR7 responses to self RNA, and we showed that disruption of this mechanism results in TLR7-dependent autoimmunity in mice. Intriguingly, this mechanism controls TLR7 but not TLR9. Our prior discoveries raise many key questions that we aim to tackle in this renewal application. We do not yet understand the molecular steps controlling the new mechanism of TLR7 regulation we discovered. Moreover, we recently identified autoimmune patients with in-born coding variants in Unc93b1, but we do not know if/how these variants cause disease. In this proposal we will also expand our studies of NA-sensing TLR regulation beyond Unc93b1 based on recently completed genome-wide CRISPR screens for genes that limit TLR7 and TLR9 responses. Both screens identified genes and pathways involved in core cell biological processes, including endosome and lysosome regulation, underscoring the paradigm that the cell biology of NA-sensing TLRs is critical to their regulation. However, the hits from the TLR7 and TLR9 screens are almost completely non-overlapping, providing exciting mechanistic insights into how these receptors are distinctly regulated. Based on these results, we propose 3 Specific Aims. Aim 1 will define the key steps by which Unc93b1 limits TLR7/8 responses and will test whether the human coding variants we have identified disrupt these steps. Aim 2 will characterize results from a genome-wide CRISPR screen that identified the cellular machinery and pathways limiting TLR7 responses to self RNA. Aim 3 will focus on TLR9 and begin to define the mechanisms that limit TLR9 responses to self DNA. The overall impact of this application comes from the central role that NA-sensing TLRs play in autoimmunity and from the benefit gained by defining the mechanisms that limit responses to self NA. Our central premise is that defining the mechanisms that regulate TLR7 and TLR9 will uncover their distinct roles in autoimmune diseases and enable more effective therapies.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).