J Exp Psychol Learn Mem Cogn
November 2024
In an influential article, Jones et al. (1995) provide evidence that auditory distraction by changing relative to repetitive auditory distracters (the changing-state effect) did not differ between a visual-verbal and visual-spatial serial recall task, providing evidence for an amodal mechanism for the representation of serial order in short-term memory that transcends modalities. This finding has been highly influential for theories of short-term memory and auditory distraction.
View Article and Find Full Text PDFFree polymannose-type oligosaccharides (fOS) are processed by cytosolic enzymes to generate Man5GlcNAc which is transferred to lysosomes and degraded. Lysosomal fOS import was demonstrated in vitro but is poorly characterized in part due to lack of convenient substrates. As chitooligosaccharides (COS, oligomers β1,4-linked GlcNAc) block [3H]Man5GlcNAc transport into lysosomes, we asked if COS are themselves transported and if so, can they be chemically modified to generate fluorescent substrates.
View Article and Find Full Text PDFCleanup and disposal of stockpiles and waste streams containing per- and polyfluoroalkyl substances (PFAS) require effective end-of-life destruction/mineralization technologies. Two classes of PFAS, perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs), are commonly found in legacy stockpiles, industrial waste streams, and as environmental pollutants. Continuous flow supercritical water oxidation (SCWO) reactors have been shown to destroy several PFAS and aqueous film-forming foams.
View Article and Find Full Text PDFVisual short-term memory (vSTM) is often measured via continuous-report tasks whereby participants are presented with stimuli that vary along a continuous dimension (e.g., colour) with the goal of memorising the stimulus features.
View Article and Find Full Text PDFJ Exp Psychol Learn Mem Cogn
July 2022
The synthesis of glycosyl-β-1-(phosphino)-phosphonates is a challenge since it has not yet been described. In this paper, we report an innovative synthetic method for their preparation from Glc-, Man-, and GlcAc- lactone derivatives. The proposed original strategy involves the addition of the corresponding δ-hexonolactones onto the dianion of (methylphosphino) phosphonate as a key step, followed by dehydration and stereoselective addition of dihydrogen on the resulting double bond.
View Article and Find Full Text PDFUDP-glucose (UDP-Glc) is synthesized by -encoded UDP-Glc pyrophosphorylase (UGP) and is required for glycoconjugate biosynthesis and galactose metabolism because it is a uridyl donor for galactose-1-P (Gal1P) uridyltransferase. Chinese hamster lung fibroblasts harboring a hypomrphic UGP(G116D) variant display reduced UDP-Glc levels and cannot grow if galactose is the sole carbon source. Here, these cells were cultivated with glucose in either the absence or presence of galactose in order to investigate glycoconjugate biosynthesis and galactose metabolism.
View Article and Find Full Text PDFMammalian protein -glycosylation requires the transfer of an oligosaccharide containing 2 residues of N-acetylglucosamine, 9 residues of mannose and 3 residues of glucose (GlcMan GlcNAc) from GlcManGlcNAc-diphospho (PP)-dolichol (DLO) onto proteins in the endoplasmic reticulum (ER). Under some pathophysiological conditions, DLO biosynthesis is perturbed, and truncated DLO is hydrolyzed to yield oligosaccharyl phosphates (OSP) via unidentified mechanisms. DLO diphosphatase activity (DLODP) was described in vitro, but its characterization is hampered by a lack of convenient non-radioactive substrates.
View Article and Find Full Text PDFHum Mutat
July 2019
ALG3-CDG is one of the very rare types of congenital disorder of glycosylation (CDG) caused by variants in the ER-mannosyltransferase ALG3. Here, we summarize the clinical, biochemical, and genetic data of four new ALG3-CDG patients, who were identified by a type I pattern of serum transferrin and the accumulation of Man GlcNAc -PP-dolichol in LLO analysis. Additional clinical symptoms observed in our patients comprise sensorineural hearing loss, right-descending aorta, obstructive cardiomyopathy, macroglossia, and muscular hypertonia.
View Article and Find Full Text PDFBackground: Congenital disorders of glycosylation (CDG) includes ALG8 deficiency, a protein N-glycosylation defect with a broad clinical spectrum. If most of the 15 previously reported patients present an early-onset multisystem severe disease and early death, three patients including the cas princeps, present long-term survival and less severe symptoms.
Methods: In order to further characterize ALG8-CDG, two new ALG8 patients are described and mRNA analyses of the ALG8-CDG cas princeps were effected.
Citronellyl- and solanesyl-based dolichol linked oligosaccharide (DLO) analogs were synthesized and tested along with undecaprenyl compounds for their ability to inhibit the release of [H]OSP from [H]DLO by mammalian liver DLO diphosphatase activity. Solanesyl (C45) and undecaprenyl (C55) compounds were 50-500 fold more potent than their citronellyl (C10)-based counterparts, indicating that the alkyl chain length is important for activity. The relative potency of the compounds within the citronellyl series was different to that of the solanesyl series with citronellyl diphosphate being 2 and 3 fold more potent than citronellyl-PP-GlcNAc and citronellyl-PP-GlcNAc, respectively; whereas solanesyl-PP-GlcNAc and solanesyl-PP-GlcNAc were 4 and 8 fold more potent, respectively, than solanesyl diphosphate.
View Article and Find Full Text PDFWe reported an oligosaccharide diphosphodolichol (DLO) diphosphatase (DLODP) that generates dolichyl-phosphate and oligosaccharyl phosphates (OSPs) from DLO in vitro. This enzyme could underlie cytoplasmic OSP generation and promote dolichyl-phosphate recycling from truncated endoplasmic reticulum (ER)-generated DLO intermediates. However, during subcellular fractionation, DLODP distribution is closer to that of a Golgi apparatus (GA) marker than those of ER markers.
View Article and Find Full Text PDFJ Lipid Res
June 2016
Oligosaccharyl phosphates (OSPs) are hydrolyzed from oligosaccharide-diphosphodolichol (DLO) during protein N-glycosylation by an uncharacterized process. An OSP-generating activity has been reported in vitro, and here we asked if its biochemical characteristics are compatible with a role in endoplasmic reticulum (ER)-situated DLO regulation. We demonstrate a Co(2+)-dependent DLO diphosphatase (DLODP) activity that splits DLO into dolichyl phosphate and OSP.
View Article and Find Full Text PDFThe C10orf2 gene encodes Twinkle, a protein involved in mitochondrial DNA (mtDNA) replication. Twinkle mutations cause mtDNA deletion or depletion and are associated with a large spectrum of clinical symptoms including dominant progressive external ophthalmoplegia (adPEO), infantile-onset spinocerebellar ataxia (IOSCA), and early-onset encephalopathy. The diagnosis remains difficult because of the wide range of symptoms and lack of association with specific metabolic changes.
View Article and Find Full Text PDFThe primary function of peptide N-glycanase (PNGase) is thought to be the deglycosylation of endoplasmic reticulum associated degradation (ERAD) substrates. However, inhibition of PNGase appears to have little effect upon the destruction rate of many ERAD substrates, and recent data demonstrate deglycosylation-independent functions for PNGase. Whatever the roles of PNGase turn out to be, the identification of a patient presenting with PNGase deficiency will advance our understanding of the importance of this multifunctional protein in human physiology.
View Article and Find Full Text PDFIn Saccharomyces cerevisiae, proteins with misfolded lumenal, membrane, and cytoplasmic domains are cleared from the endoplasmic reticulum (ER) by ER-associated degradation (ERAD)-L, -M, and -C, respectively. ERAD-L is N-glycan-dependent and is characterized by ER mannosidase (Mns1p) and ER mannosidase-like protein (Mnl1p), which generate Man(7)GlcNAc(2) (d1) N-glycans with non-reducing α1,6-mannosyl residues. Glycoproteins bearing this motif bind Yos9p and are dislocated into the cytoplasm and then deglycosylated by peptide N-glycanase (Png1p) to yield free oligosaccharides (fOS).
View Article and Find Full Text PDFBackground: During mammalian protein N-glycosylation, 20% of all dolichol-linked oligosaccharides (LLO) appear as free oligosaccharides (fOS) bearing the di-N-acetylchitobiose (fOSGN2), or a single N-acetylglucosamine (fOSGN), moiety at their reducing termini. After sequential trimming by cytosolic endo beta-N-acetylglucosaminidase (ENGase) and Man2c1 mannosidase, cytosolic fOS are transported into lysosomes. Why mammalian cells generate such large quantities of fOS remains unexplored, but fOSGN2 could be liberated from LLO by oligosaccharyltransferase, or from glycoproteins by NGLY1-encoded Peptide-N-Glycanase (PNGase).
View Article and Find Full Text PDFBackground: Biosynthesis of the dolichol linked oligosaccharide (DLO) required for protein N-glycosylation starts on the cytoplasmic face of the ER to give Man(5)GlcNAc(2)-PP-dolichol, which then flips into the ER for further glycosylation yielding mature DLO (Glc(3)Man(9)GlcNAc(2)-PP-dolichol). After transfer of Glc(3)Man(9)GlcNAc(2) onto protein, dolichol-PP is recycled to dolichol-P and reused for DLO biosynthesis. Because de novo dolichol synthesis is slow, dolichol recycling is rate limiting for protein glycosylation.
View Article and Find Full Text PDFWe report the cloning of three splice variants of the FUT10 gene, encoding for active alpha-l-fucosyltransferase-isoforms of 391, 419, and 479 amino acids, and two splice variants of the FUT11 gene, encoding for two related alpha-l-fucosyltransferases of 476 and 492 amino acids. The FUT10 and FUT11 appeared 830 million years ago, whereas the other alpha1,3-fucosyltransferases emerged 450 million years ago. FUT10-391 and FUT10-419 were expressed in human embryos, whereas FUT10-479 was cloned from adult brain and was not found in embryos.
View Article and Find Full Text PDFDuring protein N-glycosylation in mammalian cells, free oligosaccharides (fOS) are generated from lipid-linked oligosaccharides by a pyrophosphatase activity and oligosaccharyltransferase and from misfolded glycoproteins by peptide:N-glycanase in both the ER and cytoplasm. Trafficking machinery comprising oligosaccharide-specific ER and lysosomal transporters, an endo-beta-N-acetyl-glucosaminidase, and the cytosolic M2C1 mannosidase drives a flux of fOS from the ER to cytoplasm and from the cytoplasm into lysosomes where fOS are degraded. Transport of fOS out of the ER is normally efficient and if inhibited causes fOS to be secreted via the Golgi apparatus.
View Article and Find Full Text PDFAn efficient and convergent method for the synthesis of mannose-1-phosphate prodrugs is described as a potential therapy for congenital disorders of glycosylation-Ia (CDG-Ia). The key feature of the proposed approach is the silver assisted nucleophilic substitution of 2,3,4,6-tetra-O-protected-alpha-d-mannopyranosyl bromides with various silver phosphate salts to afford mono, di, and tri-mannopyranosyl phosphates. A preliminary biological evaluation of the synthesized phosphate prodrugs has been carried out.
View Article and Find Full Text PDFGeneral hospitals have commonly involved a wide range of medical specialists in the care of unselected medical emergency admissions. In 1999, the Royal Liverpool University Hospital, a 915-bed hospital with a busy emergency service, changed its system of care for medical emergencies to allow early placement of admitted patients under the care of the most appropriate specialist team, with interim care provided by specialist acute physicians on an acute medicine unit - a system we have termed 'specialty triage'. Here we describe a retrospective study in which all 133,509 emergency medical admissions from February 1995 to January 2003 were analysed by time-series analysis with correction for the underlying downward trend from 1995 to 2003.
View Article and Find Full Text PDFCongenital disorders of glycosylation (CDG) type I (CDG I) are rare autosomal recessive diseases caused by deficiencies in the assembly of the dolichol-linked oligosaccharide (DLO) that is required for N-glycoprotein biosynthesis. CDG Ie is due to a defect in the synthesis of dolichyl-phosphoryl-mannose (Dol-P-Man), which is needed for DLO biosynthesis as well as for other glycosylation pathways. Human Dol-P-Man synthase is a heterotrimeric complex composed of DPM1p, DPM2p, and DPM3p, with DPM1p being the catalytic subunit.
View Article and Find Full Text PDFTwo highly conserved eukaryotic gene products of unknown function showing homology to glycosyltransferases involved in the second steps of bacterial peptidoglycan (Murg) and capsular polysaccharide (Cps14f/Cps14g) biosynthesis have been identified in silico. The amino acid sequence of the eukaryotic protein that is homologous to the lipid acceptor- and membrane-associating N-terminal domain of Murg and the Cps14f beta4-galactosyltransferase enhancer protein is predicted to possess a cleavable signal peptide and transmembrane helices. The other eukaryotic protein is predicted to possess neither transmembrane regions nor a signal peptide but is homologous to the UDP-sugar binding C-terminal domain of Murg and the Cps14g beta4-galactosyltransferase.
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