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151.
Mandel U; Hassan H; Therkildsen MH; Rygaard J; Jakobsen MH; Juhl BR; Dabelsteen E; Clausen H 《Glycobiology》1999,9(1):43-52
Mucin-type O-glycosylation is initiated by a large family of UDP- GalNAc:
polypeptide N -acetyl-galactosaminyltransferases (GalNAc- transferases).
Individual GalNAc-transferases appear to have different functions and
Northern analysis indicates that they are differently expressed in
different organs. This suggests that O-glycosylation may vary with the
repertoire of GalNAc-transferases expressed in a given cell. In order to
study the repertoire of GalNAc-transferases in situ in tissues and changes
in tumors, we have generated a panel of monoclonal antibodies (MAbs) with
well defined specificity for human GalNAc-T1, -T2, and -T3. Application of
this panel of novel antibodies revealed that GalNAc- transferases are
differentially expressed in different cell lines, in spermatozoa, and in
oral mucosa and carcinomas. For example, GalNAc-T1 and -T2 but not -T3 were
highly expressed in WI38 cells, and GalNAc-T3 but not GalNAc-T1 or -T2 was
expressed in spermatozoa. The expression patterns in normal oral mucosa
were found to vary with cell differentiation, and for GalNAc-T2 and -T3
this was reflected in oral squamous cell carcinomas. The expression pattern
of GalNAc-T1 was on the other hand changed in tumors to either total loss
or expression in cytological poorly differentiated tumor cells, where the
normal undifferentiated cells lacked expression. These results demonstrate
that the repertoire of GalNAc-transferases is different in different cell
types and vary with cellular differentiation, and malignant transformation.
The implication of this is not yet fully understood, but it suggests that
specific changes in sites of O-glycosylation of proteins may occur as a
result of changes in the repertoire of GalNAc-transferases.
相似文献
152.
Abstract. Data referring to changes in vegetation composition resulting from cattle exclosure and ploughing in a Portuguese pasture dominated by annuals were used to test hypotheses regarding the biology of species favoured or eliminated by disturbance in semi-natural herbaceous communities. These hypotheses were tested in two ways. First we compared the distribution of six a priori groups – grasses, small rosettes, large rosettes, small species with leafy stems, large species with leafy stems, legumes – across grazed, ploughed and undisturbed plots. In a second set of analyses we examined changes in the frequencies of individual biological attributes in response to grazing and ploughing. These analyses were carried out separately for grasses and dicot forbs. Overall, the species composition showed little response to either grazing or ploughing, though species dominance changed. This lack of responsiveness of species composition was attributed to the long history of intensive land use which has resulted in the loss of disturbance-intolerant species over entire landscapes. When considering a priori groups, small rosettes were indifferent to disturbance. grazing and ploughing showed that dominated. Large rosettes, large species with leafy stems and legumes were generally intolerant to both grazing and ploughing, though individual species may increase in response to disturbance. Small species with leafy stems were the only group favoured by grazing whereas ploughing favoured grasses. As to individual traits, grazing excluded large grass species with heavy seeds and promoted a flat rosette canopy structure and a small size, along with a moderate dormancy and protected inflorescences. In forbs, grazing favoured small species, as expected, while it excluded tall species, and, in contrast to earlier results, a rosette canopy. These attributes were consistent with responses of the a priori groups, though it would not have been possible to reconstruct groups directly from the attribute list. Ploughing had no effect on any of the forb traits. As to grass traits, flat- and short-statured species increased and heavy-seeded species decreased. Our analysis revealed two advantages of establishing plant functional classifications within life forms. Subgroups within forbs had contrasting types of behaviour. For the same trait patterns could differ within the grass group from within the forb group. Finally, this analysis emphasizes the need for plant functional classifications aiming at the identification of syndromes of co-occurring attributes rather than of lists of isolated traits of which actual combinations are not specified. 相似文献
153.
Inflammatory platelet-activating factor-like phospholipids in oxidized low density lipoproteins are fragmented alkyl phosphatidylcholines. 总被引:4,自引:0,他引:4
G K Marathe S S Davies K A Harrison A R Silva R C Murphy H Castro-Faria-Neto S M Prescott G A Zimmerman T M McIntyre 《The Journal of biological chemistry》1999,274(40):28395-28404
Oxidation of human low density lipoprotein (LDL) generates proinflammatory mediators and underlies early events in atherogenesis. We identified mediators in oxidized LDL that induced an inflammatory reaction in vivo, and activated polymorphonuclear leukocytes and cells ectopically expressing human platelet-activating factor (PAF) receptors. Oxidation of a synthetic phosphatidylcholine showed that an sn-1 ether bond confers an 800-fold increase in potency. This suggests that rare ether-linked phospholipids in LDL are the likely source of PAF-like activity in oxidized LDL. Accordingly, treatment of oxidized LDL with phospholipase A(1) greatly reduced phospholipid mass, but did not decrease its PAF-like activity. Tandem mass spectrometry identified traces of PAF, and more abundant levels of 1-O-hexadecyl-2-(butanoyl or butenoyl)-sn-glycero-3-phosphocholines (C(4)-PAF analogs) in oxidized LDL that comigrated with PAF-like activity. Synthesis showed that either C(4)-PAF was just 10-fold less potent than PAF as a PAF receptor ligand and agonist. Quantitation by gas chromatography-mass spectrometry of pentafluorobenzoyl derivatives shows the C(4)-PAF analogs were 100-fold more abundant in oxidized LDL than PAF. Oxidation of synthetic alkyl arachidonoyl phosphatidylcholine generated these C(4)-PAFs in abundance. These results show that quite minor constituents of the LDL phosphatidylcholine pool are the exclusive precursors for PAF-like bioactivity in oxidized LDL. 相似文献
154.
The mouse T cell receptor: structural heterogeneity of molecules of normal T cells defined by xenoantiserum 总被引:30,自引:1,他引:29
We have previously demonstrated that T lymphomas may express clonally specific epitopes that are carried by a T-cell-restricted, disulfide-bonded heterodimeric glycoprotein. We have used a monoclonal antibody, 124-40, to isolate the lymphoma-specific antigen and raise a xenoantiserum to the molecule. This antiserum immunoprecipitates a family of disulfide-bonded dimers from normal thymocytes and T cells, but is unreactive with B cells. Peptide maps prepared after limited proteolytic digestion indicate that the molecules from the different cell populations have homologous primary structures. Comparison of two-dimensional tryptic peptide maps indicate that, in addition to several common peptides, the molecules exhibit considerable structural heterogeneity. Taken together, these data indicate that the T-cell-specific heteroduplex has regions of constant and variable structure consistent with the properties expected for the T cell antigen receptor. 相似文献
155.
Integrin-dependent Control of Translation: Engagement of Integrin αIIbβ3 Regulates Synthesis of Proteins in Activated Human Platelets 下载免费PDF全文
Ravinder Pabla Andrew S. Weyrich Dan A. Dixon Paul F. Bray Thomas M. McIntyre Stephen M. Prescott Guy A. Zimmerman 《The Journal of cell biology》1999,144(1):175-184
It has been proposed that the plasma membrane of many cell types contains cholesterol-sphingolipid-rich microdomains. Here, we analyze the role of these microdomains in promoting oligomerization of the bacterial pore-forming toxin aerolysin. Aerolysin binds to cells, via glycosyl phosphatidylinositol-anchored receptors, as a hydrophilic soluble protein that must polymerize into an amphipathic ring-like complex to form a pore. We first show that oligomerization can occur at >10(5)-fold lower toxin concentration at the surface of living cells than in solution. Our observations indicate that it is not merely the number of receptors on the target cell that is important for toxin sensitivity, but their ability to associate transiently with detergent resistant microdomains. Oligomerization appears to be promoted by the fact that the toxin bound to its glycosyl phosphatidylinositol-anchored receptors, can be recruited into these microdomains, which act as concentration devices. 相似文献
156.
Kimberley B. Ritter David R. Jordan Scott C. Chapman Ian D. Godwin Emma S. Mace C. Lynne McIntyre 《Molecular breeding : new strategies in plant improvement》2008,22(3):367-384
QTL for stem sugar-related and other agronomic traits were identified in a converted sweet (R9188) × grain (R9403463-2-1)
sorghum population. QTL analyses were conducted using phenotypic data for 11 traits measured in two field experiments and
a genetic map comprising 228 SSR and AFLP markers grouped into 16 linkage groups, of which 11 could be assigned to the 10
sorghum chromosomes (SBI-01 to SBI-10). QTL were identified for all traits and were generally co-located to five locations
(SBI-01, SBI-03, SBI-05, SBI-06 and SBI-10). QTL alleles from R9188 were detected for increased sucrose content and sugar
content on SBI-01, SBI-05 and SBI-06. R9188 also contributed QTL alleles for increased Brix on SBI-05 and SBI-06, and increased
sugar content on SBI-03. QTL alleles from R9403463-2-1 were found for increased sucrose content and sucrose yield on SBI-10,
and increased glucose content on SBI-07. QTL alleles for increased height, later flowering and greater total dry matter yield
were located on SBI-01 of R9403463-2-1, and SBI-06 of R9188. QTL alleles for increased grain yield from both R9403463-2-1
and R9188 were found on SBI-03. As an increase in stem sugars is an important objective in sweet sorghum breeding, the QTL
identified in this study could be further investigated for use in marker-assisted selection of sweet sorghum. 相似文献
157.
Phospholipids containing sn-2 polyunsaturated fatty acyl residues are primary targets of oxidizing radicals, producing proapoptotic and membrane perturbing fragmented phospholipids. The only known phospholipases that specifically select these oxidized and/or short-chained phospholipids as substrates are mammalian group VII phospholipases A2s that were purified and cloned as PAF acetylhydrolases. Platelet-activating factor (PAF) is a short-chained phospholipid, and whether these enzymes actually are PAF hydrolases or evolved as oxidized phospholipid phospholipases is unknown. The fission yeast Schizosaccharomyces pombe, which does not form or use PAF as a signaling molecule, contains an open-reading frame potentially homologous to mammalian group VII phospholipase A2s. We cloned this SPBC106.11c locus and expressed it in distantly related Saccharomyces cerevisiae that lack homologous sequences. The S. pombe locus encoded a functional phospholipase A2, now renamed plg7+, that hydrolyzed PAF and a synthetic oxidized phospholipid. Expression of human type II PAF acetylhydrolase or S. pombe Plg7p enhanced the viability of S. cerevisiae subjected to oxidative stress. We conclude that a single-celled organism with an exceedingly spare genome still expresses an unusually discriminating phospholipase A2, and that selective hydrolysis of phospholipid oxidation products is an early, and critical, way to overcome oxidative membrane damage and oxidant-induced cell death. 相似文献
158.
Molecular dissection of variation in carbohydrate metabolism related to water-soluble carbohydrate accumulation in stems of wheat 总被引:2,自引:0,他引:2
Xue GP McIntyre CL Jenkins CL Glassop D van Herwaarden AF Shorter R 《Plant physiology》2008,146(2):441-454
Water-soluble carbohydrates (WSCs; composed of mainly fructans, sucrose [Suc], glucose [Glc], and fructose) deposited in wheat (Triticum aestivum) stems are important carbon sources for grain filling. Variation in stem WSC concentrations among wheat genotypes is one of the genetic factors influencing grain weight and yield under water-limited environments. Here, we describe the molecular dissection of carbohydrate metabolism in stems, at the WSC accumulation phase, of recombinant inbred Seri/Babax lines of wheat differing in stem WSC concentrations. Affymetrix GeneChip analysis of carbohydrate metabolic enzymes revealed that the mRNA levels of two fructan synthetic enzyme families (Suc:Suc 1-fructosyltransferase and Suc:fructan 6-fructosyltransferase) in the stem were positively correlated with stem WSC and fructan concentrations, whereas the mRNA levels of enzyme families involved in Suc hydrolysis (Suc synthase and soluble acid invertase) were inversely correlated with WSC concentrations. Differential regulation of the mRNA levels of these Suc hydrolytic enzymes in Seri/Babax lines resulted in genotypic differences in these enzyme activities. Down-regulation of Suc synthase and soluble acid invertase in high WSC lines was accompanied by significant decreases in the mRNA levels of enzyme families related to sugar catabolic pathways (fructokinase and mitochondrion pyruvate dehydrogenase complex) and enzyme families involved in diverting UDP-Glc to cell wall synthesis (UDP-Glc 6-dehydrogenase, UDP-glucuronate decarboxylase, and cellulose synthase), resulting in a reduction in cell wall polysaccharide contents (mainly hemicellulose) in the stem of high WSC lines. These data suggest that differential carbon partitioning in the wheat stem is one mechanism that contributes to genotypic variation in WSC accumulation. 相似文献
159.
Todd Sformo F. Kohl J. McIntyre P. Kerr J. G. Duman B. M. Barnes 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(7):897-902
Freeze tolerance and freeze avoidance are typically described as mutually exclusive strategies for overwintering in animals.
Here we show an insect species that combines both strategies. Individual fungus gnats, collected in Fairbanks, Alaska, display
two freezing events when experimentally cooled and different rates of survival after each event (mean ± SEM: −31.5 ± 0.2°C,
70% survival and −50.7 ± 0.4°C, 0% survival). To determine which body compartments froze at each event, we dissected the abdomen
from the head/thorax and cooled each part separately. There was a significant difference between temperature levels of abdominal
freezing (−30.1 ± 1.1°C) and head/thorax freezing (−48.7 ± 1.3°C). We suggest that freezing is initially restricted to one
body compartment by regional dehydration in the head/thorax that prevents inoculative freezing between the freeze-tolerant
abdomen (71.0 ± 0.8% water) and the supercooled, freeze-sensitive head/thorax (46.6 ± 0.8% water). 相似文献
160.
James Kempson Junqing Guo Jagabandhu Das Robert V. Moquin Steven H. Spergel Scott H. Watterson Charles M. Langevine Alaric J. Dyckman Mark Pattoli James R. Burke XiaoXia Yang Kathleen M. Gillooly Kim W. McIntyre Laishun Chen John H. Dodd Murray McKinnon Joel C. Barrish William J. Pitts 《Bioorganic & medicinal chemistry letters》2009,19(10):2646-2649
A new series of tricyclic-based inhibitors of IKK have been derived from an earlier lead compound. The synthesis and structure–activity relationships (SAR) are described. Compound 4k inhibited TNF production in rats stimulated with LPS. 相似文献