Dual Effect of Organogermanium Compound THGP on RIG-I-Mediated Viral Sensing and Viral Replication during Influenza a Virus Infection.

The interaction of viral nucleic acid with protein factors is a crucial process for initiating viral polymerase-mediated viral genome replication while activating pattern recognition receptor (PRR)-mediated innate immune responses. It has previously been reported that a hydrolysate of Ge-132, 3-(trihydroxygermyl) propanoic acid (THGP), shows a modulatory effect on microbial infections, inflammation, and immune responses. However, the detailed mechanism by which THGP can modify these processes during viral infections remained unknown. Here, we show that THGP can specifically downregulate type I interferon (IFN) production in response to stimulation with a cytosolic RNA sensor RIG-I ligand 5'-triphosphate RNA (3pRNA) but not double-stranded RNA, DNA, or lipopolysaccharide. Consistently, treatment with THGP resulted in the dose-dependent suppression of type I IFN induction upon infections with influenza virus (IAV) and vesicular stomatitis virus, which are known to be mainly sensed by RIG-I. Mechanistically, THGP directly binds to the 5'-triphosphate moiety of viral RNA and competes with RIG-I-mediated recognition. Furthermore, we found that THGP can directly counteract the replication of IAV but not EMCV (encephalitismyocarditis virus), by inhibiting the interaction of viral polymerase with RNA genome. Finally, IAV RNA levels were significantly reduced in the lung tissues of THGP-treated mice when compared with untreated mice. These results suggest a possible therapeutic implication of THGP and show direct antiviral action, together with the suppressive activity of innate inflammation.

Regulation of an adaptor protein STING by Hsp90ß to enhance innate immune responses against microbial infections.

Stimulator of interferon genes (STING) plays important roles in the DNA-mediated innate immune responses. However, the regulatory mechanism of STING in terms of stabilization is not fully understood. Here, we identified the chaperone protein Hsp90s as novel STING interacting proteins. Treatment with an Hsp90 inhibitor 17-AAG and knockdown of Hsp90ß but not Hsp90α reduced STING at protein level, resulted in the suppression of IFN induction in response to stimulation with cGAMP, and infections with HSV-1 and Listeria monocytogenes. Collectively, our results suggest that the control of STING protein by Hsp90ß is a critical biological process in the DNA sensing pathways.

Expression of Lhx9 isoforms in the developing gonads of Rana rugosa.

Lhx9 is a LIM-homeodomain (HD) transcription factor. Transcripts of the Lhx9 gene are present in the urogenital ridges of mouse embryos. In Lhx9-deficient mice, a discrete gonad is not formed (Birk et al., 2000). To date, however, the role of Lhx9 in gonad formation has not been studied in animals other than chicks and mice. Thus, this study was aimed at determining whether or not Lhx9 is expressed in the developing gonads of amphibians. We first isolated cDNAs of Lhx9 and four isoforms, named Lhx9alpha, beta, gamma and delta, from the frog Rana rugosa. All the isoforms lacked the last 14 amino acids of the HD (the DNA-binding motif). RT-PCR analysis revealed that Lhx9 and Lhx9alpha were highly expressed in the ovary, testis, brain and heart of adult frogs. However, neither Lhx9 nor any of the four isoforms was expressed in the pancreas and kidney. When their expression in the developing gonads of R. rugosa was examined by RT-PCR, transcripts of Lhx9 and Lhx9alpha were detected with no sexual dimorphism during sex determination. Lhx9gamma and Lhx9delta were also expressed, but at a low level. In contrast, the Lhx9beta transcript was hardly detected. In addition, in situ hybridization analysis showed that R. rugosa Lhx9 was expressed in somatic cells in the developing gonad and mesonephros far before sex determination. Taken together, Lhx9 and its four isoforms are probably involved in organogenesis in R. rugosa. All the isoforms may function as an endogenous dominant-negative form of Lhx9 in this species.