Cascade Catalytic Nanoparticles Selectively Alkalize Cancerous Lysosomes to Suppress Cancer Progression and Metastasis.

Lysosomes are critical in modulating the progression and metastasis for various cancers. There is currently an unmet need for lysosomal alkalizers that can selectively and safely alter the pH and inhibit the function of cancer lysosomes. Here an effective, selective, and safe lysosomal alkalizer is reported that can inhibit autophagy and suppress tumors in mice. The lysosomal alkalizer consists of an iron oxide core that generates hydroxyl radicals (•OH) in the presence of excessive H+ and hydrogen peroxide inside cancer lysosomes and cerium oxide satellites that capture and convert •OH into hydroxide ions. Alkalized lysosomes, which display impaired enzyme activity and autophagy, lead to cancer cell apoptosis. It is shown that the alkalizer effectively inhibits both local and systemic tumor growth and metastasis in mice. This work demonstrates that the intrinsic properties of nanoparticles can be harnessed to build effective lysosomal alkalizers that are both selective and safe.

Arg-GlcNAcylation on TRADD by NleB and SseK1 Is Crucial for Bacterial Pathogenesis.

Death receptor signaling is critical for cell death, inflammation, and immune homeostasis. Hijacking death receptors and their corresponding adaptors through type III secretion system (T3SS) effectors has been evolved to be a bacterial evasion strategy. NleB from enteropathogenic Escherichia coli (EPEC) and SseK1/2/3 from Salmonella enterica serovar Typhimurium (S. Typhimurium) can modify some death domain (DD) proteins through arginine-GlcNAcylation. Here, we performed a substrate screen on 12 host DD proteins with conserved arginine during EPEC and Salmonella infection. NleB from EPEC hijacked death receptor signaling through tumor necrosis factor receptor 1 (TNFR1)-associated death domain protein (TRADD), FAS-associated death domain protein (FADD), and receptor-interacting serine/threonine-protein kinase 1 (RIPK1), whereas SseK1 and SseK3 disturbed TNF signaling through the modification of TRADD Arg235/Arg245 and TNFR1 Arg376, respectively. Furthermore, mouse infection studies showed that SseK1 but not SseK3 rescued the bacterial colonization deficiency contributed by the deletion of NleBc (Citrobacter NleB), indicating that TRADD was the in vivo substrate. The result provides an insight into the mechanism by which attaching and effacing (A/E) pathogen manipulate TRADD-mediated signaling and evade host immune defense through T3SS effectors.

Auto Arginine-GlcNAcylation Is Crucial for Bacterial Pathogens in Regulating Host Cell Death.

Many Gram-negative bacterial pathogens utilize the type III secretion system (T3SS) to inject virulence factors, named effectors, into host cells. These T3SS effectors manipulate host cellular signaling pathways to facilitate bacterial pathogenesis. Death receptor signaling plays an important role in eukaryotic cell death pathways. NleB from enteropathogenic Escherichia coli (EPEC) and SseK1/3 from Salmonella enterica serovar Typhimurium (S. Typhimurium) are T3SS effectors. They are defined as a family of arginine GlcNAc transferase to modify a conserved arginine residue in the death domain (DD) of the death receptor TNFR and their corresponding adaptors to hijack death receptor signaling. Here we identified that these enzymes, NleB, SseK1, and SseK3 could catalyze auto-GlcNAcylation. Residues, including Arg13/53/159/293 in NleB, Arg30/158/339 in SseK1, and Arg153/184/305/335 in SseK3 were identified as the auto-GlcNAcylation sites by mass spectrometry. Mutation of the auto-modification sites of NleB, SseK1, and SseK3 abolished or attenuated the capability of enzyme activity toward their death domain targets during infection. Loss of this ability led to the increased susceptibility of the cells to TNF- or TRAIL-induced cell death during bacterial infection. Overall, our study reveals that the auto-GlcNAcylation of NleB, SseK1, and SseK3 is crucial for their biological activity during infection.

Corrigendum: Identification and evolution of a plant cell wall specific glycoprotein glycosyl transferase, ExAD.

This corrects the article DOI: 10.1038/srep45341.

Identification and evolution of a plant cell wall specific glycoprotein glycosyl transferase, ExAD.

Extensins are plant cell wall glycoproteins that act as scaffolds for the deposition of the main wall carbohydrate polymers, which are interlocked into the supramolecular wall structure through intra- and inter-molecular iso-di-tyrosine crosslinks within the extensin backbone. In the conserved canonical extensin repeat, Ser-Hyp4, serine and the consecutive C4-hydroxyprolines (Hyps) are substituted with an α-galactose and 1-5 ß- or α-linked arabinofuranoses (Arafs), respectively. These modifications are required for correct extended structure and function of the extensin network. Here, we identified a single Arabidopsis thaliana gene, At3g57630, in clade E of the inverting Glycosyltransferase family GT47 as a candidate for the transfer of Araf to Hyp-arabinofuranotriose (Hyp-ß1,4Araf-ß1,2Araf-ß1,2Araf) side chains in an α-linkage, to yield Hyp-Araf4 which is exclusively found in extensins. T-DNA knock-out mutants of At3g57630 showed a truncated root hair phenotype, as seen for mutants of all hitherto characterized extensin glycosylation enzymes; both root hair and glycan phenotypes were restored upon reintroduction of At3g57630. At3g57630 was named Extensin Arabinose Deficient transferase, ExAD, accordingly. The occurrence of ExAD orthologs within the Viridiplantae along with its' product, Hyp-Araf4, point to ExAD being an evolutionary hallmark of terrestrial plants and charophyte green algae.