Mechanisms of IncRNA/RBP regulation of macrophage function for control of T. cruzi infection

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ABSTRACT Trypanosoma cruzi (T. cruzi or Tc), the causative agent of Chagas cardiomyopathy, is widely distributed in Latin America and the southern half of the USA. It is estimated that >8 million recorded cases and ~ 120 million people at risk in Latin America. The host immune response is critical for outcome of the disease. Macrophages (Mϕs) function as control switches of the immune system and maintain balance between pro- and anti- inflammatory response. In context to Chagas disease, peripheral and tissue Mϕs play an essential role against acute Tc infection. However, Mϕs fail to eliminate the parasite, and progress to chronic disease phase. The mechanisms by which pathogenic isolates of Tc hijack the host innate and adaptive immune system to ensure its survival in the host are largely unknown. An in-depth understanding of the biology of host-pathogen interactions is important for the development of preventative and treatment countermeasures against Tc infection. Long non-coding RNAs (lncRNAs, ˃ 200 nucleotides) include a diverse class of RNAs that do not encode proteins. Among them, a class of lncRNA that binds to RNA binding protein (RBP) is regarded to play a critical role in regulation of post-transcriptional / translational machinery and protein synthesis. Whether lncRNA-RBP interactions shape host immunity remains an underexplored opportunity for control of parasitic infection. Through systematic analysis of lncRNA arrays and a confirmatory approach, we have identified transcript variants 1-3 of lncRNA Morrbid as highly upregulated in Mφs infected with Tc. Unbiased screening of cross-linking immunoprecipitation-sequencing databases and subsequent RNA immunoprecipitation (RIP) assays demonstrated that lncRNA Morrbid-3 binds to Zinc finger protein 36 (ZFP36) RBP. ZFP36 expression was increased in Mφs infected by Tc, and RNAi mediated manipulation of Morrbid-3 expression strengthened proinflammatory cytokine/chemokine signaling pathways and resulted in clearance of intracellular parasites. The central hypothesis to be tested in this proposal is that Tc utilizes the regulation of lncRNA Morrbid- 3/ZFP36 RBP complex to attenuate innate immunity and ensure its intracellular survival in host. We will employ molecular biology and immunology approaches to test this hypothesis in independent, yet mechanistically related aims. In Aim 1, our objectives are to determine if lncRNA Morrbid-3 exerts anti-apoptotic and immunomodulatory effects, and depletion of Morrbid-3 promotes parasite clearance by Mφ. In Aim 2, we will examine the molecular mechanism of Morrbid-3/ZFP36 complex mediated immune regulation of Mφ in response to Tc infection. The impact of the proposed studies will be discovery of novel mechanisms by which lncRNA Morrbid- 3/ZFP36 RBP complex determines the outcomes of Tc infection. Importantly, we will determine if small molecule inhibitors of Morrbid-3/ZFP36 interaction will offer novel therapeutic avenues to control Tc infection.