Autophagy mediates the cellular response to nutrient deprivation, protein aggregation, and pathogen invasion in human. Dysfunction of autophagy has been implicated in multiple human diseases including cancer. The identification of novel autophagy factors in mammalian cells will provide critical mechanistic insights into how this complicated cellular pathway responds to a broad range of challenges. Here, we report the cloning of an autophagy-specific protein that we called Barkor (Beclin 1-associated autophagy-related key regulator) through direct interaction with Beclin 1 in the human phosphatidylinositol 3-kinase class III complex. Barkor shares 18% sequence identity and 32% sequence similarity with yeast Atg14. Elimination of Barkor expression by RNA interference compromises starvation-and rapamycin-induced LC3 lipidation and autophagosome formation. Overexpression of Barkor leads to autophagy activation and increased number and enlarged volume of autophagosomes. Tellingly, Barkor is also required for suppression of the autophagy-mediated intracellular survival of Salmonella typhimurium in mammalian cells. Mechanistically, Barkor competes with UV radiation resistance associated gene product (UVRAG) for interaction with Beclin 1, and the complex formation of Barkor and Beclin1 is required for their localizations to autophagosomes. Therefore, we define a regulatory signaling pathway mediated by Barkor that positively controls autophagy through Beclin 1 and represents a potential target for drug development in the treatment of human diseases implicated in autophagic dysfunction.Atg14 ͉ autophagosome ͉ LC3 ͉ Salmonella ͉ UVRAG

Translated regions distinct from annotated coding sequences have emerged as essential elements of the proteome. This includes upstream open reading frames (uORFs) present in mRNAs controlled by the integrated stress response (ISR) that show “privileged” translation despite inhibited eukaryotic initiation factor 2–guanosine triphosphate–initiator methionyl transfer RNA (eIF2·GTP·Met-tRNAiMet). We developed tracing translation by T cells to directly measure the translation products of uORFs during the ISR. We identified signature translation events from uORFs in the 5′ untranslated region of binding immunoglobulin protein (BiP) mRNA (also called heat shock 70-kilodalton protein 5mRNA) that were not initiated at the start codon AUG. BiP expression during the ISR required both the alternative initiation factor eIF2A and non–AUG-initiated uORFs. We propose that persistent uORF translation, for a variety of chaperones, shelters select mRNAs from the ISR, while simultaneously generating peptides that could serve as major histocompatibility complex class I ligands, marking cells for recognition by the adaptive immune system.

Severe acute pancreatitis (SAP) still remains a clinical challenge, not only for its high mortality but the uncontrolled inflammatory progression from acute pancreatitis (AP) to SAP. Cell death, including apoptosis and necrosis are critical pathology of AP, since the severity of pancreatitis correlates directly with necrosis and inversely with apoptosis Therefore, regulation of cell death from necrosis to apoptosis may have practicably therapeutic value. X-linked inhibitor of apoptosis protein (XIAP) is the best characterized member of the inhibitor of apoptosis proteins (IAP) family, but its function in AP remains unclear. In the present study, we investigated the potential role of XIAP in regulation of cell death and inflammation during acute pancreatitis. The in vivo pancreatitis model was induced by the administration of cerulein with or without lipopolysaccharide (LPS) or by the administration of l-arginine in wild-type or XIAP-deficient mice, and ex vivo model was induced by the administration of cerulein+LPS in AR42J cell line following XIAP inhibition. The severity of acute pancreatitis was determined by serum amylase activity and histological grading. XIAP deletion on cell apoptosis, necrosis and inflammatory response were examined. Caspases activities, nuclear factor-κB (NF-κB) activation and receptor-interacting protein kinase1 (RIP1) degradation were assessed by western blot. Deletion of XIAP resulted in the reduction of amylase activity, decrease of NF-κB activation and less release of TNF-α and IL-6, together with increased caspases activities and RIP1 degradation, leading to enhanced apoptosis and reduced necrosis in pancreatic acinar cells and ameliorated the severity of acute pancreatitis. Our results indicate that deletion of XIAP switches cell death away from necrosis to apoptosis and decreases the inflammatory response, effectively attenuating the severity of AP/SAP. The critical role of XIAP in cell death and inflammation suggests that inhibition of XIAP represents a potential therapeutic strategy for the treatment of acute pancreatitis.

The role of peroxisome proliferator – activated receptor- δ (PPAR δ) gene in colon carcinogenesis remains highly controversial. Here, we established nude mice xenograft model using a human colon cancer cell line KM12C either with PPAR δ silenced or normal. The xenografts in PPAR δ-silenced group grew significantly larger and heavier with less differentiation, promoted cell proliferation, increased expression of vascular endothelial growth factor (VEGF) and similar apoptosis index compared with those of PPAR δ-normal group. After treated with the specific VEGF inhibitor bevacizumab, the capacities of growth and proliferation of xenografts were decreased in both groups while still significantly higher in PPAR δ-silenced group than in PPAR δ-normal group. Administration of PPAR δ agonist significantly decreased VEGF expression in PPAR δ-normal KM12C cells but not in PPAR δ-silenced cells. These findings demonstrate that, knockdown of PPAR δ promotes the growth of colon cancer by inducing less differentiation, accelerating the proliferation and VEGF expression of tumor cells in vivo, and reduces tumor sensitivity to bevacizumab. This study indicates that PPAR δ attenuates colon carcinogenesis.

Summary Reliable identification of individual chromosomes in eukaryotic species is the foundation for comparative chromosome synteny and evolutionary studies. Unfortunately, chromosome identification has been a major challenge for plants with small chromosomes, such as the Citrus species. We developed oligonucleotide‐based chromosome painting probes for all nine chromosomes in Citrus maxima (Pummelo). We were able to identify all C. maxima chromosomes in the same metaphase cells using multiple rounds of sequential fluorescence in situ hybridization with the painting probes. We conducted comparative chromosome painting analysis in six different Citrus and related species. We found that each painting probe hybridized to only a single chromosome in all other five species, suggesting that the six species have maintained a complete chromosomal synteny after more than 9 million years of divergence. No interchromosomal rearrangement was identified in any species. These results support the hypothesis that karyotypes of woody species are more stable than herbaceous plants because woody plants need a longer period to fix chromosome structural variants in natural populations.