Toll-like Receptor 8 Stability Is Regulated by Ring Finger 216 in Response to Circulating MicroRNAs

TLR8 (Toll-like receptor 8) is an intracellular pattern recognition receptor that senses RNA in endosomes to initiate innate immune signaling through NF-κB, and mechanisms regulating TLR8 protein abundance are not completely understood. Protein degradation is a cellular process controlling protein concentrations, accomplished largely through ubiquitin transfer directed by E3 ligase proteins to substrates. In the present study, we show that TLR8 has a short half-life in THP-1 monocytes (∼1 h) and that TLR8 is ubiquitinated and degraded in the proteasome. Treatment with the TLR8 agonist R848 causes rapid depletion of TLR8 concentrations at early time points, an effect blocked by proteasomal inhibition. We show a novel role for RNF216 (ring finger protein 216), an E3 ligase that targets TLR8 for ubiquitination and degradation. RNF216 overexpression reduces TLR8 concentrations, whereas RNF216 knockdown stabilizes TLR8. We describe a potential role for TLR8 activation by circulating RNA ligands in humans with acute respiratory distress syndrome (ARDS): Plasma and extracted RNA fractions from subjects with ARDS activated TLR8 in vitro. MicroRNA (miRNA) expression profiling revealed several circulating miRNAs from subjects with ARDS. miRNA mimics promoted TLR8 proteasomal degradation in THP-1 cells. These data show that TLR8 proteasomal disposal through RNF216 in response to RNA ligands regulates TLR8 cellular concentrations and may have implications for innate immune signaling. In addition, TLR8 activation by circulating RNA ligands may be a previously underrecognized stimulus contributing to excessive innate immune signaling characteristic of ARDS.

Novel findings from determination of common expressed plasma exosomal microRNAs in patients with psoriatic arthritis, psoriasis vulgaris, rheumatoid arthritis, and gouty arthritis

Adrenocortical carcinoma (ACC) is a rare but aggressive malignancy. Localized tumors can be treated successfully with surgical excision, but the presence of micrometastases, recurrence, and advanced disease are associated with high mortality rates, despite the use of chemotherapy with etoposide, doxorubicin, cisplatin (EDP), and mitotane. During the past decade, the characterization of ACC using genomic profiling and next-generation sequencing (NGS) has resulted in the proposed new targeted therapies for patients with advanced ACC. In 2018, the European Society of Endocrinology in collaboration with the European Network for the Study of Adrenal Tumors (ENSAT) published clinical practice guidelines for the management of ACC. However, the authors of these new guidelines concluded that the evidence to support clinical management recommendations remains weak, as there remains a requirement for large-scale controlled clinical trials to support new targeted therapies. This review discusses the recent developments in the diagnosis, staging, and management of ACC, and the molecular changes that may be the basis for future personalized or targeted therapy, if supported by data from clinical trials.