ER Stress, Secretory Granule Biogenesis, and Insulin

Insulin is secreted from pancreatic β-cells, and the high demand of insulin biosynthesis is known to cause β-cell dysfunction in patients with type 2 diabetes mellitus. The insulin biosynthetic pathway has been extensively studied and is still an exciting area for future studies. In this chapter, first, we focus on proinsulin biosynthetic pathway in the endoplasmic reticulum (ER) and recent progress of our knowledge about ER stress. We discuss about how ER stress is involved in the development of diabetes. Second, we focus on the formation of insulin secretory granules. The biogenesis of secretory granules has been explored for several decades; however, it still has been debated and has yet to be understood. We review the current knowledge about the secretory granules and discuss about the problems for future studies

Microdetermination of parathions by thermo- and ultra-violet decomposition products

By means of the thin layer chromatography (TLC) a study was carried out on the decomposition of methyl parathion, ethyl parathion and sumithion when exposed to heat or ultra-violet irradiation. The results are briefly summarized as follows. 1. Parathions, when exposed to heat, form hydrolysates and such 0-analog as paraoxon as well as S-alky1 isomers. 2. When parathions are exposed to ultra-violet rays at 365 m&#956; and 254 m&#956;, the rate of decomposition is extremely slow. For example, when exposed to such rays in Petri dish for 5 hours, only a small amount of S-alkyl isomer is formed. 3. After heating parathions in a small test tube and conducting TLC, when each 0-analog and S-alkyl isomer above mentioned is confirmed, it is possible to identify a minute amount of each parathion by this method, and thus this method is feasible to apply to practical poison examination as a rapid and simple qualitative examination method.</p

Generation of mouse models for type 1 diabetes by selective depletion of pancreatic beta cells using toxin receptor-mediated cell knockout

AbstractBy using the toxin receptor-mediated cell knockout (TRECK) method, we have generated two transgenic (Tg) murine lines that model type 1 (insulin-dependent) diabetes. The first strain, C.B-17/Icr-Prkdcscid/Prkdcscid-INS-TRECK-Tg, carries the diphtheria toxin receptor (hDTR) driven by the human insulin gene promoter, while the other strain, C57BL/6-ins2(BAC)-TRECK-Tg, expresses hDTR cDNA under the control of the mouse insulin II gene promoter. With regard to the C.B-17/Icr-Prkdcscid/Prkdcscid-INS-TRECK-Tg strain, only one of three Tg strains exhibited proper expression of hDTR in pancreatic β cells. By contrast, hDTR was expressed in the pancreatic β cells of all four of the generated C57BL/6-ins2(BAC)-TRECK-Tg strains. Hyperglycemia, severe ablation of pancreatic β cells and depletion of serum insulin were observed within 3days after the administration of diphtheria toxin (DT) in these Tg mice. Subcutaneous injection of a suitable dosage of insulin was sufficient for recovery from hyperglycemia in all of the examined strains. Using the C.B-17/Icr-Prkdcscid/Prkdcscid-INS-TRECK-Tg model, we tried to perform regenerative therapeutic approaches: allogeneic transplantation of pancreatic islet cells from C57BL/6 and xenogeneic transplantation of CD34+ human umbilical cord blood cells. Both approaches successfully rescued C.B-17/Icr-Prkdcscid/Prkdcscid-INS-TRECK-Tg mice from hyperglycemia caused by DT administration. The high specificity with which DT causes depletion in pancreatic β cells of these Tg mice is highly useful for diabetogenic research

A novel Rac1-GSPT1 signaling pathway controls astrogliosis following central nervous system injury

Astrogliosis (i.e. glial scar), which is comprised primarily of proliferated astrocytes at the lesion site and migrated astrocytes from neighboring regions, is one of the key reactions in determining outcomes after CNS injury. In an effort to identify potential molecules/pathways that regulate astrogliosis, we sought to determine whether Rac/Rac-mediated signaling in astrocytes represents a novel candidate for therapeutic intervention following CNS injury. For these studies, we generated mice with Rac1 deletion under the control of the GFAP (glial fibrillary acidic protein) promoter (GFAP-Cre;Rac1(flox/flox)). GFAP-Cre;Rac1(flox/flox) (Rac1-KO) mice exhibited better recovery after spinal cord injury and exhibited reduced astrogliosis at the lesion site relative to control. Reduced astrogliosis was also observed in Rac1-KO mice following microbeam irradiation-induced injury. Moreover, knockdown (KD) or KO of Rac1 in astrocytes (LN229 cells, primary astrocytes, or primary astrocytes from Rac1-KO mice) led to delayed cell cycle progression and reduced cell migration. Rac1-KD or Rac1-KO astrocytes additionally had decreased levels of GSPT1 (G(1) to S phase transition 1) expression and reduced responses of IL-1β and GSPT1 to LPS treatment, indicating that IL-1β and GSPT1 are downstream molecules of Rac1 associated with inflammatory condition. Furthermore, GSPT1-KD astrocytes had cell cycle delay, with no effect on cell migration. The cell cycle delay induced by Rac1-KD was rescued by overexpression of GSPT1. Based on these results, we propose that Rac1-GSPT1 represents a novel signaling axis in astrocytes that accelerates proliferation in response to inflammation, which is one important factor in the development of astrogliosis/glial scar following CNS injury

SMN promotes mitochondrial metabolic maturation during myogenesis by regulating the MYOD-miRNA axis

脊髄性筋萎縮症における骨格筋病変の発症メカニズムの一部を解明. 京都大学プレスリリース. 2023-01-17.Pathogenesis of skeletal muscle lesions in spinal muscular atrophy. 京都大学プレスリリース. 2023-02-17.Spinal muscular atrophy (SMA) is a congenital neuromuscular disease caused by the mutation or deletion of the survival motor neuron 1 (SMN1) gene. Although the primary cause of progressive muscle atrophy in SMA has classically been considered the degeneration of motor neurons, recent studies have indicated a skeletal muscle–specific pathological phenotype such as impaired mitochondrial function and enhanced cell death. Here, we found that the down-regulation of SMN causes mitochondrial dysfunction and subsequent cell death in in vitro models of skeletal myogenesis with both a murine C2C12 cell line and human induced pluripotent stem cells. During myogenesis, SMN binds to the upstream genomic regions of MYOD1 and microRNA (miR)-1 and miR-206. Accordingly, the loss of SMN down-regulates these miRs, whereas supplementation of the miRs recovers the mitochondrial function, cell survival, and myotube formation of SMN-deficient C2C12, indicating the SMN-miR axis is essential for myogenic metabolic maturation. In addition, the introduction of the miRs into ex vivo muscle stem cells derived from Δ7-SMA mice caused myotube formation and muscle contraction. In conclusion, our data revealed novel transcriptional roles of SMN during myogenesis, providing an alternative muscle-oriented therapeutic strategy for SMA patients

Negative feedback by IRE1β optimizes mucin production in goblet cells

In mammals, the prototypical endoplasmic reticulum (ER) stress sensor inositol-requiring enzyme 1 (IRE1) has diverged into two paralogs. IRE1α is broadly expressed and mediates the unconventional splicing of X-box binding protein 1 (XBP1) mRNA during ER stress. By contrast, IRE1β is expressed selectively in the digestive tract, and its function remains unclear. Here, we report that IRE1β plays a distinctive role in mucin-secreting goblet cells. In IRE1β-/- mice, aberrant mucin 2 (MUC2) accumulated in the ER of goblet cells, accompanied by ER distension and elevated ER stress signaling such as increased XBP1 mRNA splicing. In contrast, conditional IRE1α-/- mice showed no such ER distension but a marked decrease in spliced XBP1 mRNA. mRNA stability assay revealed that MUC2 mRNA was greatly stabilized in IRE1β-/- mice. These findings suggest that in goblet cells, IRE1β, but not IRE1α, promotes efficient protein folding and secretion in the ER by optimizing the level of mRNA encoding their major secretory product, MUC2

Lactams. XXVI. Regioselectivity in the mercuric acetate- edetic acid oxidation of the ethyl 1-(2-aryl-2-hydroxyethyl)-3- ethyl-4-piperidineacetate system: Enhancement by a benzyloxy group in the aryl moiety and by the 3,4-cis configuration

A quantitative analytical study to determine the isomer ratios of the 6-piperidones (type 7) and 2-piperidones (type 5) produced by the mercuric acetate-edetic acid (EDTA) oxidation of 1-(2-aryl-2-hydroxyethyl)-3-alkylpiperidines (±)-4c, d, f, h, 4e, g, i, j, and (±)-38 was carried out. It has been found that all the substrates with a benzyloxy group in the aryl moiety, regardless of its location, undergo oxidation at the 6-position preferentially as compared with the debenzyloxy derivatives such as (±)-4a, b. Comparison of the quantitative data from 4e and (±)-4f with those from (±)-4b indicated that the cis acetate chain at the 4-position increases the extent of the 6-oxidation, whereas a trans acetate chain at the same position has little effect. These two factors enhance the practical value of the "cincholoipon-incorporating method" for chiral syntheses of the 1-type Alangium alkaloids, in which the mercuric acetate-EDTA oxidation of 4e, g, i, j to the 6-piperidones (type 3)is one of the key synthetic operations