The mechanisms by which tumor microenvironments modulate nucleic acid–mediated innate immunity remain unknown. Here we identify the receptor TIM-3 as key in circumventing the stimulatory effects of nucleic acids in tumor immunity. Tumor-associated dendritic cells (DCs) in mouse tumors and patients with cancer had high expression of TIM-3. DC-derived TIM-3 suppressed innate immune responses through the recognition of nucleic acids by Toll-like receptors and cytosolic sensors via a galectin-9-independent mechanism. In contrast, TIM-3 interacted with the alarmin HMGB1 to interfere with the recruitment of nucleic acids into DC endosomes and attenuated the therapeutic efficacy of DNA vaccination and chemotherapy by diminishing the immunogenicity of nucleic acids released from dying tumor cells. Our findings define a mechanism whereby tumor microenvironments suppress antitumor immunity mediated by nucleic acids.

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Edited by Shou-Wei DingKeywords: RNA silencing Suppressor of gene silencing 3 RNA-dependent RNA polymerase 6 Dicer-like 4 Processing body Arabidopsis a b s t r a c t Suppressor of gene silencing 3 (SGS3) is involved in RNA-dependent RNA polymerase 6 (RDR6)-dependent small-interfering RNA (siRNA) pathways in Arabidopsis. However, the roles of SGS3 in those pathways are unclear. Here, we show that SGS3 interacts and colocalizes with RDR6 in cytoplasmic granules. Interestingly, the granules containing SGS3 and RDR6 (named SGS3/RDR6-bodies) were distinct from the processing bodies where mRNAs are decayed and/or stored. Microscopic analyses and complementation experiments using SGS3-deletion mutants suggested that proper localization of SGS3 is important for its function. These results provide novel insights into RDR6-dependent siRNA formation in plants.

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Influenza A virus (IAV) infection is initiated by the attachment of the viral glycoprotein hemagglutinin (HA) to sialic acid on the host cell surface. However, the sialic acid-containing receptor crucial for IAV infection has remained unidentified. Here, we show that HA binds to the voltage-dependent Ca channel Ca1.2 to trigger intracellular Ca oscillations and subsequent IAV entry and replication. IAV entry was inhibited by Ca channel blockers (CCBs) or by knockdown of Ca1.2. The CCB diltiazem also inhibited virus replication in vivo. Reintroduction of wild-type but not the glycosylation-deficient mutants of Ca1.2 restored Ca oscillations and virus infection in Ca1.2-depleted cells, demonstrating the significance of Ca1.2 sialylation. Taken together, we identify Ca1.2 as a sialylated host cell surface receptor that binds HA and is critical for IAV entry.