MDA5, a viral double-stranded RNA (dsRNA) receptor, shares sequence similarity and signaling pathways with RIG-I yet plays essential functions in antiviral immunity through distinct specificity for viral RNA. Revealing the molecular basis for the functional divergence, we report here the crystal structure of MDA5 bound to dsRNA, which shows how, using the same domain architecture, MDA5 recognizes the internal duplex structure, whereas RIG-I recognizes the terminus of dsRNA. We further show that MDA5 uses direct protein-protein contacts to stack along dsRNA in a head-to-tail arrangement, and that the signaling domain (tandem CARD), which decorates the outside of the core MDA5 filament, also has an intrinsic propensity to oligomerize into an elongated structure that activates the signaling adaptor, MAVS. These data support a model in which MDA5 uses long dsRNA as a signaling platform to cooperatively assemble the core filament, which in turn promotes stochastic assembly of the tandem CARD oligomers for signaling.
Background The aim of this study is to report a novel, multicenter experience with the diverticular peroral endoscopic myotomy (D-POEM) technique in the management of esophageal diverticula.
Methods This is a multicenter, international, retrospective study involving three centers. D-POEM was performed using the principles of submucosal endoscopy.
Results A total of 11 patients with an esophageal diverticulum (Zenker’s 7, mid-esophagus 1, epiphrenic 3) were included. The mean size of the esophageal diverticula was 34.5 mm. The overall technical success rate of D-POEM was 90.9 %, with a mean procedure time of 63.2 minutes. There were no adverse events. Clinical success was achieved in 100 % (10 /10), with a decrease in mean dysphagia score from 2.7 to 0.1 (P < 0.001) during a median follow-up of 145 days (interquartile range 126 – 273).
Conclusion Endoscopic management of esophageal diverticula using the novel technique of D-POEM appears promising. This first case series on D-POEM suggests that the procedure is feasible, safe, and effective in the management of esophageal diverticula. D-POEM offers the distinct advantage of ensuring a complete septotomy. Larger studies are needed to confirm these intriguing results.
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