Dual Role of TRPV2 in the STING-mediated innate immune response

Washington University, Saint Louis MO

Investigators

Abstract

PROJECT ABSTRACT The overall goal of this proposal is to establish and elucidate novel functions of the ion channel TRPV2 in controlling the cGAS/STING-mediated innate immune response. Serving as the first line of defense against microbial pathogens, the cGAS/STING-mediated innate immune system also senses and responds to self-DNA in the cytosol derived from the nuclear and mitochondrial genomes. Upon the binding of cGAS to cytosolic DNA, a series of signaling events occur to transduce the immune signal through multiple factors (cGAMP, STING, TBK1, IRF3, NF-B) and organelles (ER, Golgi, nucleus) to induce the expression of type I interferons and inflammatory cytokines. This innate immune response promotes pathogen restriction, and directly influences tissue maintenance, tumorigenesis, and cancer treatment outcome. However, despite intensive studies, our understanding of the mechanisms and regulation of innate immune signaling remains limited. In particular, precisely how STING is regulated on the ER and how it integrates various signals before translocating to Golgi to induce a balanced immune response remain outstanding questions. Our recent discovery of a physical and functional interaction between STING and the ion channel TRPV2 on the ER in a Ca2+-dependent genome protection pathway provides an exciting new avenue to address these fundamental questions. In this pathway, cytosolic DNA induced by replication stress triggers cGAS activation and cGAMP production. The binding of cGAMP to STING causes its dissociation from TRPV2 on the ER, leading to TRPV2 derepression and Ca2+ release. The resulting elevation of cytoplasmic Ca2+ then activates CaMKK2 and downstream kinase AMPK to protect the genome from EXO1-mediated aberrant replication fork processing. Interestingly, our unpublished results strongly suggest this TRPV2/Ca2+-dependent pathway also directly regulates STING activation and innate immune signaling. Building on our findings, in this grant application we describe a series of experiments to delineate the multifaceted functions of TRPV2 in the innate immune response. In Aim 1, we will elucidate the mechanisms by which TRPV2-mediated Ca2+ release activates the STING-dependent innate immune pathway. In addition, we will determine whether the loss of Trpv2 can rescue the phenotypes of a Trex1-/- mouse model for the autoimmune disorder Aicardi-Goutières syndrome (AGS). In Aim 2, we will define the role of the physical interaction of TRPV2 in STING regulation and the functional relationship between TRPV2 and another ER protein STIM1 in this regulation. These studies will significantly advance our understanding of the innate immune response system and facilitate the development of new therapeutic strategies for autoimmune diseases, chronic inflammation and cancer.