Phosphorylation of eukaryotic initiation factor 2␣ (eIF-2␣) is typically associated with stress responses and causes a reduction in protein synthesis. However, we found high phosphorylated eIF-2␣ (eIF-2␣[P]) levels in nonstressed pancreata of mice. Administration of glucose stimulated a rapid dephosphorylation of eIF-2␣. Among the four eIF-2␣ kinases present in mammals, PERK is most highly expressed in the pancreas, suggesting that it may be responsible for the high eIF-2␣[P] levels found therein. We describe a Perk knockout mutation in mice. Pancreata of Perk ؊/؊ mice are morphologically and functionally normal at birth, but the islets of Langerhans progressively degenerate, resulting in loss of insulin-secreting beta cells and development of diabetes mellitus, followed later by loss of glucagon-secreting alpha cells. The exocrine pancreas exhibits a reduction in the synthesis of several major digestive enzymes and succumbs to massive apoptosis after the fourth postnatal week. Perk ؊/؊ mice also exhibit skeletal dysplasias at birth and postnatal growth retardation. Skeletal defects include deficient mineralization, osteoporosis, and abnormal compact bone development. The skeletal and pancreatic defects are associated with defects in the rough endoplasmic reticulum of the major secretory cells that comprise the skeletal system and pancreas. The skeletal, pancreatic, and growth defects are similar to those seen in human Wolcott-Rallison syndrome.

MicroRNAs (miRNAs) are noncoding RNAs with 18–26 nucleotides; they pair with target mRNAs to regulate gene expression and produce significant changes in various physiological and pathological processes. In recent years, the interaction between miRNAs and their target genes has become one of the mainstream directions for drug development. As a large-scale biological database that mainly provides miRNA–target interactions (MTIs) verified by biological experiments, miRTarBase has undergone five revisions and enhancements. The database has accumulated >2 200 449 verified MTIs from 13 389 manually curated articles and CLIP-seq data. An optimized scoring system is adopted to enhance this update’s critical recognition of MTI-related articles and corresponding disease information. In addition, single-nucleotide polymorphisms and disease-related variants related to the binding efficiency of miRNA and target were characterized in miRNAs and gene 3′ untranslated regions. miRNA expression profiles across extracellular vesicles, blood and different tissues, including exosomal miRNAs and tissue-specific miRNAs, were integrated to explore miRNA functions and biomarkers. For the user interface, we have classified attributes, including RNA expression, specific interaction, protein expression and biological function, for various validation experiments related to the role of miRNA. We also used seed sequence information to evaluate the binding sites of miRNA. In summary, these enhancements render miRTarBase as one of the most research-amicable MTI databases that contain comprehensive and experimentally verified annotations. The newly updated version of miRTarBase is now available at https://miRTarBase.cuhk.edu.cn/.

Phosphorylation of eukaryotic initiation factor-2 (eIF2) by pancreatic eIF2 kinase (PEK), induces a program of translational expression in response to accumulation of malfolded protein in the endoplasmic reticulum (ER). This study addresses the mechanisms activating PEK, also designated PERK or EIF2AK3. We describe the characterization of two regions in the ER luminal portion of the transmembrane PEK that carry out distinct functions in the regulation of this eIF2 kinase. The first region mediates oligomerization between PEK polypeptides, and deletion of this portion of PEK blocked induction of eIF2 kinase activity. The second characterized region of PEK facilitates interaction with ER chaperones. In the absence of stress, PEK associates with ER chaperones GRP78 (BiP) and GRP94, and this binding is released in response to ER stress. ER luminal sequences flanking the transmembrane domain are required for GRP78 interaction, and deletion of this portion of PEK led to its activation even in the absence of ER stress. These results suggest that this ER chaperone serves as a repressor of PEK activity, and release of ER chaperones from PEK when misfolded proteins accumulate in the ER induces gene expression required to enhance the protein folding capacity of the ER.

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a two-electron reductase responsible for detoxification of quinones and also bioactivation of certain quinones. It is abnormally overexpressed in many tumors and intimately linked with multiple carcinogenic processes. NQO1 is considered to be a cancer-specific target for therapy but currently available NQO1 inhibitors have not yet led to chemotherapeutic success. Utilization of NOQ1's ability to bioactivate chemotherapeutic quinones, however, has emerged as a promising selective anticancer therapy. On the basis of the different levels of NQO1 between cancer and normal cells, the catalytic property of NQO1 has recently been exploited to develop effective probes for cancer detection. This article summarizes the most significant advances concerning the discovery and development of NQO1 inhibitors, NQO1-directed chemotherapeutic quinones, and NQO1-activated optical probes, along with the prospects and potential obstacles in this research area.

No abstract