Centralized Modularity of N-Linked Glycosylation Pathways in Mammalian Cells

Glycosylation is a highly complex process to produce a diverse repertoire of cellular glycans that are attached to proteins and lipids. Glycans are involved in fundamental biological processes, including protein folding and clearance, cell proliferation and apoptosis, development, immune responses, and pathogenesis. One of the major types of glycans, N-linked glycans, is formed by sequential attachments of monosaccharides to proteins by a limited number of enzymes. Many of these enzymes can accept multiple N-linked glycans as substrates, thereby generating a large number of glycan intermediates and their intermingled pathways. Motivated by the quantitative methods developed in complex network research, we investigated the large-scale organization of such N-linked glycosylation pathways in mammalian cells. The N-linked glycosylation pathways are extremely modular, and are composed of cohesive topological modules that directly branch from a common upstream pathway of glycan synthesis. This unique structural property allows the glycan production between modules to be controlled by the upstream region. Although the enzymes act on multiple glycan substrates, indicating cross-talk between modules, the impact of the cross-talk on the module-specific enhancement of glycan synthesis may be confined within a moderate range by transcription-level control. The findings of the present study provide experimentally-testable predictions for glycosylation processes, and may be applicable to therapeutic glycoprotein engineering

Glucagon-like peptide-1 (GLP-1) and the regulation of human invariant natural killer T cells: lessons from obesity, diabetes and psoriasis

Aims/hypothesis The innate immune cells, invariant natural killer T cells (iNKT cells), are implicated in the pathogenesis of psoriasis, an inflammatory condition associated with obesity and other metabolic diseases, such as diabetes and dyslipidaemia. We observed an improvement in psoriasis severity in a patient within days of starting treatment with an incretin-mimetic, glucagon-like peptide-1 (GLP-1) receptor agonist. This was independent of change in glycaemic control. We proposed that this unexpected clinical outcome resulted from a direct effect of GLP-1 on iNKTcells. Methods We measured circulating and psoriatic plaque iNKT cell numbers in two patients with type 2 diabetes and psoriasis before and after commencing GLP-1 analogue therapy. In addition, we investigated the in vitro effects of GLP-1 on iNKT cells and looked for a functional GLP-1 receptor on these cells. Results The Psoriasis Area and Severity Index improved in both patients following 6 weeks of GLP-1 analogue therapy. This was associated with an alteration in iNKT cell number, with an increased number in the circulation and a decreased number in psoriatic plaques. The GLP-1 receptor was expressed on iNKT cells, and GLP-1 induced a dose-dependent inhibition of iNKT cell cytokine secretion, but not cytolytic degranulation in vitro. Conclusions/interpretation The clinical effect observed and the direct interaction between GLP-1 and the immune system raise the possibility of therapeutic applications for GLP-1 in inflammatory conditions such as psoriasis

Ecosystem development after mangrove wetland creation : plant–soil change across a 20-year chronosequence

This paper is not subject to U.S. copyright. The definitive version was published in Ecosystems 15 (2012): 848-866, doi:10.1007/s10021-012-9551-1.Mangrove wetland restoration and creation efforts are increasingly proposed as mechanisms to compensate for mangrove wetland losses. However, ecosystem development and functional equivalence in restored and created mangrove wetlands are poorly understood. We compared a 20-year chronosequence of created tidal wetland sites in Tampa Bay, Florida (USA) to natural reference mangrove wetlands. Across the chronosequence, our sites represent the succession from salt marsh to mangrove forest communities. Our results identify important soil and plant structural differences between the created and natural reference wetland sites; however, they also depict a positive developmental trajectory for the created wetland sites that reflects tightly coupled plant-soil development. Because upland soils and/or dredge spoils were used to create the new mangrove habitats, the soils at younger created sites and at lower depths (10–30 cm) had higher bulk densities, higher sand content, lower soil organic matter (SOM), lower total carbon (TC), and lower total nitrogen (TN) than did natural reference wetland soils. However, in the upper soil layer (0–10 cm), SOM, TC, and TN increased with created wetland site age simultaneously with mangrove forest growth. The rate of created wetland soil C accumulation was comparable to literature values for natural mangrove wetlands. Notably, the time to equivalence for the upper soil layer of created mangrove wetlands appears to be faster than for many other wetland ecosystem types. Collectively, our findings characterize the rate and trajectory of above- and below-ground changes associated with ecosystem development in created mangrove wetlands; this is valuable information for environmental managers planning to sustain existing mangrove wetlands or mitigate for mangrove wetland losses

Cellular magnesium acquisition : an anomaly in embryonic cation homeostasis

Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Experimental and Molecular Pathology 83 (2007): 224-240, doi:10.1016/j.yexmp.2007.03.007.The intracellular dominance of magnesium ion makes clinical assessment difficult despite the critical role of Mg++ in many key functions of cells and enzymes. There is general consensus that serum Mg++ levels are not representative of the growing number of conditions for which magnesium is known to be important. There is no consensus method or sample source for testing for clinical purposes. High intracellular Mg++ in vertebrate embryos results in part from interactions of cations which influence cell membrane transport systems. These are functionally competent from the earliest stages, at least transiently held over from the unfertilized ovum. Kinetic studies with radiotracer cations, osmolar variations, media lacking one or more of the four biological cations, Na+, Mg++, K+, and Ca++, and metabolic poison 0.05 mEq/L NaF, demonstrated: (1) all four cations influence the behavior of the others, and (2) energy is required for uptake and efflux on different time scales, some against gradient. Na+ uptake is energy dependent against an efflux gradient. The rate of K+ loss is equal with or without fluoride, suggesting a lack of an energy requirement at these stages. Ca++ efflux took twice as long in the presence of fluoride, likely due in part to intracellular binding. Mg++ is anomalous in that early teleost vertebrate embryos have an intracellular content exceeding the surrounding sea water, an isolated unaffected yolk compartment, and a clear requirement for energy for both uptake and efflux. The physiological, pathological, and therapeutic roles of magnesium are poorly understood. This will change: (1) when 28Mg is once again generally available at a reasonable cost for both basic research and clinical assessment, and (2) when serum or plasma levels are determined simultaneously with intracellular values, preferably as part of complete four cation profiles. Atomic absorption spectrophotometry, energy-dispersive x-ray analysis, and inductively coupled plasma emission spectroscopy on sublingual mucosal and peripheral blood samples are potential methods of value for coordinated assessments.AEC Grant No. 134

Effective Cost-Sharing Models in Higher Education: Insights from Low-Income Students in Australian Universities

This study examines the global trend in shifting university costs from national governments to individual students and families, with a specific focus on the existing cost-sharing model in Australian higher education. The research examines the manner in which the availability of income-contingent loans (through the Higher Education Contribution Scheme, or HECS) enters into individual cost assessments and evaluative frameworks during the university exploration and search process of low-income Australian youth, and the resulting lessons that might be applied to other national contexts. Semi-structured interviews with 16 participants addressed a broad range of issues related to the development of educational aspirations, and how beliefs and attitudes about cost influenced participants’ understanding and decision-making regarding tertiary enrollment and post-graduate plans. A number of discreet and related themes emerged from analysis of the interviews, including motivations for attending university; pre-university cost considerations; self-assessments of skills, abilities, and personal traits and characteristics; general financial orientation; pre-university experiences and influences; and the role of others including family, peers, teachers and other school staff. The author concludes that the Australian system is worthy of consideration by other nations as a possible mechanism for enhancing access to higher education for individuals who might otherwise not possess the opportunity to participate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42840/1/10734_2004_Article_6373.pd

Connective tissue activation. xxxvi. the origin, variety, distribution, and biologic fate of connective tissue activating peptide–iii isoforms: characteristics in patients with rheumatic, renal, and arterial disease

Objective. To determine the origin, distribution, and biologic fate of platelet-derived connective tissue activating peptide–III (CTAP-III), to define the relative amounts of the antigen forms (CTAP-III, betathromboglobulin [Β-TG], neutrophil activating peptide–2 [NAP-2]) in plasma of normal persons and those with rheumatic or end-stage renal disease, and to define the isoforms of CTAP-III in platelets, plasma, transudates, and tissue deposits. Methods. CTAP-III in plasma was measured by enzyme-linked immunosorbent assay, and growth promoting activity of CTAP-III isoforms was tested in synovial and peritoneal cell cultures by measuring increased synthesis of 14 C-glycosaminoglycan ( 14 C-GAG) and 3 H-DNA. Isolated CTAP-III was characterized by Western blotting, microsequencing, and mass spectrometry. Results. CTAP-III was the primary isoform of this antigen family in normal platelets and platelet-rich plasma; Β-TG and NAP-2 accounted for 90%), and Β-TG was the most rare (0–1%). Deposition of CTAP-III in tissues, such as synovium, spleen, and kidney, is associated with partial processing to NAP-2–like isoforms and the potential to induce neutrophil and fibroblast activation in patients with rheumatic or end-stage renal disease.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37798/1/1780360816_ftp.pd