NF-кB promotes aggresome formation via upregulating HDAC6 and in turn maintaining Vimentin cage.

Proteasome inhibitors have been applied to anticancer therapy by accumulating toxic misfolded proteins. However, chemical inactivation of proteasome generates aggresome, a Vimentin cage-enclosed subcellular structure quarantining HDAC6-Dynein-transported misfolded proteins before the protein toxicants are degraded by autophagy. Hence, aggresome may attenuate proteasome inhibitor drugs-induced cytotoxicity. To solve the problem, it is imperative to characterize how cells assemble aggresome. By examining aggresomes in six cell lines, A549 cells were selectively studied for their bigger cell size and moderate aggresome forming activity. Aggresome grew in size upon continuous exposure of A549 cells to proteasome inhibitor MG132, and reached a mature size around 16th to 24th hour of treatment. Mechanistic studies revealed that NF-кB translocated to nucleus in MG132 treated cells, and chemical activation or knockdown of NF-кB enhanced or prohibited aggresome assembly. Further analyses showed that NF-кB upregulated HDAC6, and HDAC6 maintained Vimentin cage by interacting with Vimentin p72, a key modification of the intermediate filament contributing to aggresome formation. Remarkably, chemical inactivation of NF-кB synergized MG132-induced cell mortality. All the findings suggest that NF-кB dictates aggresome assembly via upregulating HDAC6, and NF-кB inhibitor may serve as a potential drug potentiating proteasome inhibitor medicine-induced cytotoxicity during the treatment of cancer cells.

The crescent-like Golgi ribbon is shaped by the Ajuba/PRMT5/Aurora-A complex-modified HURP.

BACKGROUND: Golgi apparatus (GA) is assembled as a crescent-like ribbon in mammalian cells under immunofluorescence microscope without knowing the shaping mechanisms. It is estimated that roughly 1/5 of the genes encoding kinases or phosphatases in human genome participate in the assembly of Golgi ribbon, reflecting protein modifications play major roles in building Golgi ribbon. METHODS: To explore how Golgi ribbon is shaped as a crescent-like structure under the guidance of protein modifications, we identified a protein complex containing the scaffold proteins Ajuba, two known GA regulators including the protein kinase Aurora-A and the protein arginine methyltransferase PRMT5, and the common substrate of Aurora-A and PRMT5, HURP. Mutual modifications and activation of PRMT5 and Aurora-A in the complex leads to methylation and in turn phosphorylation of HURP, thereby producing HURP p725. The HURP p725 localizes to GA vicinity and its distribution pattern looks like GA morphology. Correlation study of the HURP p725 statuses and GA structure, site-directed mutagenesis and knockdown-rescue experiments were employed to identify the modified HURP as a key regulator assembling GA as a crescent ribbon. RESULTS: The cells containing no or extended distribution of HURP p725 have dispersed GA membranes or longer GA. Knockdown of HURP fragmentized GA and HURP wild type could, while its phosphorylation deficiency mutant 725A could not, restore crescent Golgi ribbon in HURP depleted cells, collectively indicating a crescent GA-constructing activity of HURP p725. HURP p725 is transported, by GA membrane-associated ARF1, Dynein and its cargo adaptor Golgin-160, to cell center where HURP p725 forms crescent fibers, binds and stabilizes Golgi assembly factors (GAFs) including TRIP11, GRASP65 and GM130, thereby dictating the formation of crescent Golgi ribbon at nuclear periphery. CONCLUSIONS: The Ajuba/PRMT5/Aurora-A complex integrates the signals of protein methylation and phosphorylation to HURP, and the HURP p725 organizes GA by stabilizing and recruiting GAFs to its crescent-like structure, therefore shaping GA as a crescent ribbon. Therefore, the HURP p725 fiber serves a template to construct GA according to its shape. Video Abstract.

Construction of Spirofused Tricyclic Frameworks by NHC-Catalyzed Intramolecular Stetter Reaction of a Benzaldehyde Tether with a Cyclic Enone.

Various benzaldehyde tethers with a cyclic enone were prepared from commercially available 2-hydroxybenzaldehydes via a three-step sequence involving triflate formation, Sonogashira cross-coupling, and regioselective hydrogenation. These substrates were then exposed to an N-heterocyclic carbene, whereupon intramolecular Stetter reaction proceeded smoothly to give various spirofused tricyclic 1,4-diketones in 30-87% yields. Furaldehyde and nicotinaldehyde derivatives also participated in the reaction under the Stetter conditions.

Total Synthesis of the Proposed Structure of (±)-Nidemone.

Total synthesis of the proposed structure of (±)-nidemone has been accomplished either from 2-hydroxy-6-methoxybenzaldehyde (7) or 2-bromo-6-methoxybenzaldehyde (8) in 10 and 13 synthetic steps, respectively. Sonogashira coupling, regioselective hydrogenation, and an intramolecular Stetter reaction were the key steps in the synthesis.