Regulation of innate immunity in marine mussel Mytilus coruscus: MicroRNA Mc-novel_miR_196 targets McTLR-like1 molecule to inhibit inflammatory response and apoptosis.

Toll-like receptors (TLRs) are crucial players in immune recognition and regulation, with aberrant activation leading to autoimmune, chronic inflammatory, and infectious diseases. MicroRNAs (miRNAs) have been shown to regulate gene expression at transcriptional and post-transcriptional levels. While miRNA-mediated regulation of TLR signaling has been studied in mammals, the underlying mechanisms of TLR-miRNA interactions in molluscs remain unclear. In a previous study, one of the TLR genes potentially targeted by miRNAs was identified and named McTLR-like1. McTLR-like1 was later found to be targeted by miRNA Mc-novel_miR_196 through bioinformatic prediction. In this study, we aim to experimentally determine the interaction between McTLR-like1 and Mc-novel_miR_196, as well as their functional role in the innate immune response of molluscs. The results showed that the expression of Mc-novel_miR_196 was suppressed, while the expression of McTLR-like1 was enhanced in M. coruscus hemocytes treated with lipopolysaccharide (LPS). Moreover, in vitro assays demonstrated that Mc-novel_miR_196 directly targets the 5' UTR of McTLR-like1 and leads to the down-regulation of proinflammatory cytokines in hemocytes. In addition, co-transfection experiments confirmed that Mc-novel_miR_196 inhibits McTLR-like1 and inhibits the expression of proinflammatory cytokines. The Tunel assay also showed that Mc-novel_miR_196 inhibited apoptosis in hemocytes induced by LPS. Our findings suggest that microRNA Mc-novel_miR_196 acts as a regulator of innate immunity in M. coruscus by targeting McTLR-like1 and inhibiting inflammatory response and apoptosis. These results provide further insights into the complex molecular mechanisms underlying TLR signaling in molluscs.

Exploring the Role of a Novel Interleukin-17 Homolog from Invertebrate Marine Mussel Mytilus coruscus in Innate Immune Response: Is Negative Regulation by Mc-Novel_miR_145 the Key?

Interleukin-17 (IL-17) represents a class of proinflammatory cytokines involved in chronic inflammatory and degenerative disorders. Prior to this study, it was predicted that an IL-17 homolog could be targeted by Mc-novel_miR_145 to participate in the immune response of Mytilus coruscus. This study employed a variety of molecular and cell biology research methods to explore the association between Mc-novel_miR_145 and IL-17 homolog and their immunomodulatory effects. The bioinformatics prediction confirmed the affiliation of the IL-17 homolog with the mussel IL-17 family, followed by quantitative real-time PCR assays (qPCR) to demonstrate that McIL-17-3 was highly expressed in immune-associated tissues and responded to bacterial challenges. Results from luciferase reporter assays confirmed the potential of McIL-17-3 to activate downstream NF-κb and its targeting by Mc-novel_miR_145 in HEK293 cells. The study also produced McIL-17-3 antiserum and found that Mc-novel_miR_145 negatively regulates McIL-17-3 via western blotting and qPCR assays. Furthermore, flow cytometry analysis indicated that Mc-novel_miR_145 negatively regulated McIL-17-3 to alleviate LPS-induced apoptosis. Collectively, the current results showed that McIL-17-3 played an important role in molluscan immune defense against bacterial attack. Furthermore, McIL-17-3 was negatively regulated by Mc-novel_miR_145 to participate in LPS-induced apoptosis. Our findings provide new insights into noncoding RNA regulation in invertebrate models.