The cryo-EM structure of the human ERAD retrotranslocation complex.

Endoplasmic reticulum-associated degradation (ERAD) maintains protein homeostasis by retrieving misfolded proteins from the endoplasmic reticulum (ER) lumen into the cytosol for degradation. The retrotranslocation of misfolded proteins across the ER membrane is an energy-consuming process, with the detailed transportation mechanism still needing clarification. We determined the cryo-EM structures of the hetero-decameric complex formed by the Derlin-1 tetramer and the p97 hexamer. It showed an intriguing asymmetric complex and a putative coordinated squeezing movement in Derlin-1 and p97 parts. With the conformational changes of p97 induced by its ATP hydrolysis activities, the Derlin-1 channel could be torn into a "U" shape with a large opening to the lipidic environment, thereby forming an entry for the substrates in the ER membrane. The EM analysis showed that p97 formed a functional protein complex with Derlin-1, revealing the coupling mechanism between the ERAD retrotranslocation and the ATP hydrolysis activities.

Occurrence and distribution of estrogenic substances in the northern South China Sea.

Estrogenic substances are today among the contaminants of emerging concern. Besides naturally occurring estrogens, other natural and synthetic substances can mimic a hormonal action due to their structural resemblance to hormones, possibly affecting the endocrine system of living organisms. Estrogens have been detected in inland water bodies such as influents and effluents of waste water treatment plants as well as in rivers, but data on their distribution and variability in the marine ecosystem are still limited. Surface water samples obtained during two research cruises on the northern shelf of the South China Sea (SCS) near the Pearl River Estuary, in September 2018 and in August 2019, were investigated for estrogenic substances, namely estrone (E1), 17ß-estradiol (E2), 17α-ethinylestradiol (EE2), genistein (GEN), daidzein (DAI) and zearalenone (ZEN). Among the target analytes, the natural hormones E1 and E2, as well as the synthetic EE2, were the most abundant with maximum concentrations of 1.1 ng L-1, 0.7 ng L-1 and 0.6 ng L-1, respectively. Of substances produced by plants and fungi, GEN, DAI and ZEN, only GEN was detected (1.2 ng L-1). High concentrations occurred predominantly close to the coast, which was also reflected in the calculated estradiol equivalent quotients (up to 1.4 ng L-1). In general, the distribution of estrogenic substances observed in both years shows a regional and inter-annual variability consistent with the modeled surface current data for the SCS. Regarding single estrogenic compounds and estradiol equivalents, marine organisms in the northern SCS might be exposed to high potential risk.

Deubiquitinase USP29 promotes gastric cancer cell migration by cooperating with phosphatase SCP1 to stabilize Snail protein.

Snail is a master inducer of epithelial-mesenchymal transition (EMT) and metastasis, however, Snail protein is labile and is quickly degraded through the predominate ubiquitination-mediated proteasome pathway. Deubiquitinases (DUBs) can counteract the Snail degradation process to maintain high level of Snail protein in cancer cells. In this study, we screened a cDNA library containing 79 DUBs, and discovered that a panel of DUBs consisting of USP13, USP28, USP29, USP37, OTUD6A, and DUB3 can markedly stabilize Snail protein, with USP29 displaying the strongest activity to prevent Snail degradation. Mechanistically, USP29 enhances the interaction of Snail and SCP1, resulting in simultaneous dephosphorylation and deubiquitination of Snail and thereafter cooperative prevention of Snail degradation. Biologically, ectopic expression of USP29 promotes gastric cancer cell migration, and depletion of Snail abolishes USP29-mediated cell migration; and USP29 can be induced by major EMT and metastatic inducing factors such as TGFß, TNFα, and hypoxia. More importantly, high expression levels of Snail, USP29, and SCP1 are associated with poor survival and prognosis. Collectively, these data indicate that Snail is a crucial substrate for USP29 to promote cell migration and USP29/SCP1 complex may be new therapeutic targets to treat metastatic cancer.

PLK4 deubiquitination by Spata2-CYLD suppresses NEK7-mediated NLRP3 inflammasome activation at the centrosome.

The innate immune sensor NLRP3 assembles an inflammasome complex with NEK7 and ASC to activate caspase-1 and drive the maturation of proinflammatory cytokines IL-1ß and IL-18. NLRP3 inflammasome activity must be tightly controlled, as its over-activation is involved in the pathogenesis of inflammatory diseases. Here, we show that NLRP3 inflammasome activation is suppressed by a centrosomal protein Spata2. Spata2 deficiency enhances NLRP3 inflammasome activity both in the macrophages and in an animal model of peritonitis. Mechanistically, Spata2 recruits the deubiquitinase CYLD to the centrosome for deubiquitination of polo-like kinase 4 (PLK4), the master regulator of centrosome duplication. Deubiquitination of PLK4 facilitates its binding to and phosphorylation of NEK7 at Ser204. NEK7 phosphorylation in turn attenuates NEK7 and NLRP3 interaction, which is required for NLRP3 inflammasome activation. Pharmacological or shRNA-mediated inhibition of PLK4, or mutation of the NEK7 Ser204 phosphorylation site, augments NEK7 interaction with NLRP3 and causes increased NLRP3 inflammasome activation. Our study unravels a novel centrosomal regulatory pathway of inflammasome activation and may provide new therapeutic targets for the treatment of NLRP3-associated inflammatory diseases.