Involvement of luxS in Biofilm Formation by Capnocytophaga ochracea

Capnocytophaga ochracea is present in the dental plaque biofilm of patients with periodontitis. Biofilm cells change their phenotype through quorum sensing in response to fluctuations in cell-population density. Quorum sensing is mediated by auto-inducers (AIs). AI-2 is involved in intercellular signaling, and production of its distant precursor is catalyzed by LuxS, an enzyme involved in the activated methyl cycle. Our aim was to clarify the role of LuxS in biofilm formation by C. ochracea. Two luxS-deficient mutants, TmAI2 and LKT7, were constructed from C. ochracea ATCC 27872 by homologous recombination. The mutants produced significantly less AI-2 than the wild type. The growth rates of these mutants were similar to that of the wild-type in both undiluted Tryptic soy broth and 0.5 × Tryptic soy broth. However, according to crystal violet staining, they produced significantly less biofilm than the wild type. Confocal laser scanning microscopy and scanning electron microscopy showed that the biofilm of the TmAI2 strain had a rougher structure than that of the wild type. Complementation of TmAI-2 with extrinsic AI-2 from the culture supernatant of wild-type strain did not restore biofilm formation by the TmAI2 strain, but complementation of LKT7 strain with luxS partially restored biofilm formation. These results indicate that LuxS is involved in biofilm formation by C. ochracea, and that the attenuation of biofilm formation by the mutants is likely caused by a defect in the activated methyl cycle rather than by a loss of AI-2.     

Endoplasmic reticulium protein profiling of heat-stressed Jurkat cells by one dimensional electrophoresis and liquid chromatography tandem mass spectrometry

Proteomic study on membrane-integrated proteins in endoplasmic reticulum (ER) fractions was performed. In this study, we examined the effects of heat stress on Jurkat cells. The ER fractions were highly purified by differential centrifugation with sodium carbonate washing and acetone methanol precipitations. The ER membrane proteins were separated by one dimensional electrophoresis (1-DE), and some of the protein bands changed their abundance by heat stress, 12 of the 14 bands containing 40 and 60 ribosomal proteins whose expression level were decreased, on the contrary, 2 of the 14 bands containing ubiquitin and eukaryotic translation initiation factor 3 were increased. Heat treatment of human Jurkat cells led to an increase in the phosphorylation of PERK and eIF2α within 30 min of exposure. This was followed by an increase in the expression of the GRP78. Protein ubiquitination and subsequent degradation by the proteasome are important mechanisms regulating cell cycle, growth and differentiation, the result showed that heat stress enhanced ubiquitination modification of the microsomal proteins. The data of this study strongly suggest that heat treatment led to a significant reduction in protein expression and activated UPR, concomitant with protein hyperubiqutination in ER.     

Expression of a putative dioxygenase gene adjacent to an insertion mutation is involved in the short internodes of columnar apples (<Emphasis Type="Italic">Malus</Emphasis> × <Emphasis Type="Italic">domestica</Emphasis>)

Determining the molecular mechanism of fruit tree architecture is important for tree management and fruit production. An apple mutant ‘McIntosh Wijcik’, which was discovered as a bud mutation from ‘McIntosh’, exhibits a columnar growth phenotype that is controlled by a single dominant gene, Co. In this study, the mutation and the Co gene were analyzed. Fine mapping narrowed the Co region to a 101 kb region. Sequence analysis of the Co region and the original wild-type co region identified an insertion mutation of an 8202 bp long terminal repeat (LTR) retroposon in the Co region. Segregation analysis using a DNA marker based on the insertion polymorphism showed that the LTR retroposon was closely associated with the columnar growth phenotype. RNA-seq and RT-PCR analysis identified a promising Co candidate gene (91071-gene) within the Co region that is specifically expressed in ‘McIntosh Wijcik’ but not in ‘McIntosh’. The 91071-gene was located approximately 16 kb downstream of the insertion mutation and is predicted to encode a 2-oxoglutarate-dependent dioxygenase involved in an unknown reaction. Overexpression of the 91071-gene in transgenic tobaccos and apples resulted in phenotypes with short internodes, like columnar apples. These data suggested that the 8202 bp retroposon insertion in ‘McIntosh Wijcik’ is associated with the short internodes of the columnar growth phenotype via upregulated expression of the adjacent 91071-gene. Furthermore, the DNA marker based on the insertion polymorphism could be useful for the marker-assisted selection of columnar apples.     

Sialic acid is an essential moiety of mucin as a hydroxyl radical scavenger

In this work, we examined the antioxidant role of mucin, a typical sialic acid containing high-molecular weight glycoprotein. The function of mucin as a hydroxyl radical (.OH) scavenger was characterized using bovine submaxillary gland mucin (BSM). Non-treated BSM effectively protected DNA from the attack of .OH; however, desialylated BSM lost this potential. Moreover, we estimated the scavenging effects of BSM against .OH generated by UV irradiation of hydrogen peroxide using ESR analysis. Our results indicate that BSM has .OH scavenging ability the and sialic acid in mucin is an essential moiety to scavenge .OH.     

Translocation and activation of sphingosine kinase 1 by ceramide-1-phosphate

Sphingosine kinases (SphKs) and ceramide kinase (CerK) phosphorylate sphingosine to sphingosine-1-phosphate (S1P) and ceramide to ceramide-1-phosphate (C1P), respectively. S1P and C1P are bioactive lipids that regulate cell fate/function and human health/diseases. The translocation and activity of SphK1 are regulated by its phosphorylation of Ser ²²⁵ and by anionic lipids such as phosphatidic acid and phosphatidylserine. However, the roles of another anionic lipid C1P on SphK1 functions have not yet been elucidated, thus, we here investigated the regulation of SphK1 by CerK/C1P. C1P concentration dependently bound with and activated recombinant human SphK1. The inhibition of CerK reduced the phorbol 12-myristate 13-acetate-induced translocation of SphK1 to the plasma membrane (PM) and activation of the enzyme in membrane fractions of cells. A treatment with C1P translocated wild-type SphK1, but not the SphK1-S225A mutant, to the PM without affecting phosphorylation signaling. A cationic RxRH sequence is proposed to be a C1P-binding motif in α-type cytosolic phospholipase A ₂ and tumor necrosis factor α-converting enzyme. The mutation of four cationic amino acids to Ala in the 56-RRNHAR-61 domain in SphK1 reduced the phorbol 12-myristate 13-acetate- and C1P-induced translocation of SphK1 to the PM, however, the capacity of C1P to bind with and activate SphK1 was not affected by this mutation. In conclusion, C1P modulates SphK1 functions by interacting with multiple sites in SphK1.     

Role of sulphated tyrosine residue in influencing the biologic activity of human cholecystokinin-33

To evaluate the role of the sulphated tyrosine residue in position 27 in human cholecystokinin-33, parallel bioassay of the sulphated form of human cholecystokinin-33 and the unsulphated form of human cholecystokinin-33 was performed on the pancreatic protein secretion. Both peptides increased the protein output in a dose-related manner. However, the sulphated form possessed a considerably higher activity than the sulphated form. The relative potency of the unsulphated human cholecystokinin-33 compared to that of the sulphated human cholecystokinin-33 (taken as 1.0) was 0.08. From the results, it was suggested that the sulphated tyrosine may play an important role in controlling the activity of the longer molecular forms as well as that of the smaller forms of cholecystokinin.     

The impact of carboxy nitroxide antioxidants on irradiated ataxia telangiectasia cells

Three water-soluble carboxy nitroxide antioxidants, 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl, 4-carboxy-2,2,6,6-tetramethylpiperidin-1-yloxyl, and 3-carboxy-2,2,5,5-tetramethylpyrrolidin-1-yloxyl, show significant impact on the postirradiation survival rates of ataxia telangiectasia (A-T) cells compared to normal cells, an assay which represents a model for understanding the impact of ROS damage on the A-T phenotype. The effects of these antioxidants are much more significant than those of vitamin E or Trolox (a water-soluble vitamin E analog), studied using the same cell survival model.     

Tomato paste fraction inhibiting the formation of advanced glycation end-products

A water-soluble and low-molecular-weight fraction (SB) was obtained from tomato paste. The effects of SB on the formation of advanced glycation end-products (AGE) in protein glycation were studied by the methods of specific fluorescence, ELISA and a Western blot analysis, using the anti-AGE antibody after incubating protein with sugar. The results suggest that SB had strong inhibitory activity, in comparison with aminoguanidine as a positive control, and that the inhibitory mechanism of SB differed from that of aminoguanidine to involve trapping of reactive dicarbonyl intermediates in the early stage of glycation. SB contained an antioxidant, rutin, which showed potent inhibitory activity. The results also suggest that rutin chiefly contributed to inhibiting the formation of AGE, and that other compounds in SB may also have been related to the activity.