AIM2 and IFI16 Innate Immune Sensors for Cytosolic DNA in Prostatic Diseases

Cincinnati Va Medical Center Research, Cincinnati OH

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Abstract

DESCRIPTION (provided by applicant): Studies indicate close links between prostatic inflammation and the development of aging-associated prostatic diseases such as benign prostate hyperplasia (BPH) and prostate cancer (PC). However, the molecular mechanisms that contribute to prostatic inflammation remain largely unknown. Studies have identified a role for cytosolic double-stranded DNA (dsDNA) sensor proteins in initiating innate immune responses that contribute to chronic inflammation. These proteins include NALP3 and the interferon (IFN) - inducible AIM2 and IFI16. Upon sensing cytosolic dsDNA, the AIM2 and NALP3 proteins recruit adaptor protein ASC to form an inflammasome, which promotes the secretion of pro-inflammatory cytokines such as IL-1¿ and IL-18. However, upon sensing cytosolic dsDNA, the IFI16 protein recruits the stimulator of interferon genes (STING) protein to stimulate the expression of IFN-¿, whereas upon sensing the nuclear dsDNA the protein recruits ASC protein to form an inflammasome. Based on our preliminary observations, we hypothesize that sensing of dsDNA by AIM2 and IFI16 proteins in prostate epithelial cells (PrECs) triggers innate immune responses that contribute to an increased production of proinflammatory cytokines. Additionally, we postulate that the physical and functional interactions between the AIM2 and IFI16 proteins in PrECs activate the transcriptional activity of NF-¿B that promotes the expression of the proinflammatory cytokines and chemokines; thus, leading to the chronic prostatic inflammation. Aim # 1: We seek to identify the molecular mechanisms by which type I and type II IFNs regulate the expression levels of AIM2 protein and subcellular localization of the AIM2 and IFI16 proteins in human normal PrECs and cancer cell lines. The approaches, including gel-mobility shift assays, promoter-reporter assays, knockdown of STAT1 expression, mutational analyses, and chromatin immunoprecipitation assays (ChIPs) will be used. Aim # 2: Characterize the role of AIM2 and other DNA sensors in cytosolic DNA-triggered innate immune responses in human normal PrECs, prostate cancer cell lines, and the prostatic lesions. Specifically, we propose to: (i) investigate whether cytosolic dsDNA triggers the AIM2 and other inflammasome activation in PrECs and prostate cancer cell lines; and (ii) examine expression levels and subcellular localization of the AIM2 and other DNA sensor proteins in inflammation-associated prostatic diseases. Immunohistochemistry, microarray, and quantitative real-time PCR will be used. Aim # 3: Investigate how interactions between the AIM2 and IFI16 proteins contribute to the modulation of NF-¿B activity in PrECs. Biochemical and molecular cell biology approaches including ChIPs will be used. Significance: Proposed studies are likely to identify the molecular mechanisms through which the AIM2 and IFI16 innate immune sensors for dsDNA contribute to prostatic inflammation and the development of inflammation-associated prostatic diseases.