MDR · Structural and functional characterization of MAVS-DDX3-vRNA complex

Structural and functional characterization of MAVS-DDX3-vRNA complex

Project MDR-REP-844115-1 – Periodic Report What is the problem/issue being addressed? The mitochondrial antiviral signalling (MAVS) adaptor protein is a central signalling hub for host cells to mount an antiviral response following RNA virus infections, which is initiated by the cytosolic receptors that trigger the type-I interferon (INFs) path through the MAVS (Fig1). It has recently been shown that the RNA helicase DDX3 is a novel atypical member of the viral cytosolic receptor pool. It is required to activate the MAVS during the antiviral response. It is currently unknown how the complex partners MAVS-DDX3-viral RNA (MDR) interact for assembly and what is the MDR mechanism of action at the molecular level. Notably, silencing DDX3 or MAVS expression suppress activation of the native immune response, an event that in the physiological condition is at the front line of host defences against RNA viruses such HIV-1. However, understanding how viral RNA triggers the innate immune reaction requires the MDR structure elucidation. Moreover, these findings will exploit MDR molecular features to create a new generation of adjuvants in anti-retroviral therapy. Our research addressed the structural and functional characterization of the MDR complex by biophysical and cellular biology techniques. This work aimed to understand how cellular protein sensors interact with retroviral RNA to trigger the native immune response and induce the expression of antiviral proteins. Why is it important for society? These studies will have fundamental implications for understanding novel virus sensors and their role in innate immunity. Therefore, the central role in triggering antiviral immune response makes MDR a strategic pharmacological target. What are the overall objectives? The objectives of the project include 1) to perform FRET experiments by tagging DDX3 and the viral RNA, in order to test the hypothesis that they assemble into a supramolecular signalling platform before interacting with MAVS and triggering the immune response; 2) determination of the 3D structure of the MDR, employing cryo-Electron Microscopy (cryo-EM) and X-ray crystallography as appropriate to shed light on the key interactions involved in the complex assembly; 3) to identify and test mutation sites on DDX3 and MAVS responsible for the complex formation based on the MDR structure, able to lower the HIV-1 infection rate in vitro cells.

Data: CORDIS, © European Union