Reduced diversity of the human erythrocyte membrane sialic acids in polycythemia vera. Absence of N-glycolylneuraminic acid and characterisation of N-acetylneuraminic acid 1,7 lactone

Sialic acids from the erythrocyte (RBC) membrane of a patient suffering from polycythemia vera, a malignant orphan disorder of hematopoietic cells, was studied using GC/MS. We found that the sialic acid diversity of these membranes was drastically reduced since only four entities were identified: Neu5Ac (91.5%) and its 1,7 lactone Neu5Ac1,7L (7.5%) which is absent in normal RBC, Neu4,5Ac(2) (0.50%) and Neu4,5Ac(2) 9Lt (0.50%); in normal RBC, Neu5,7Ac(2), Neu5,9Ac(2), Neu5Ac9Lt, Neu5Ac8S and Neu, as well as traces of Kdn, were also present. Neu5Gc and its O-alkylated or O-acetylated derivatives, which are considered by various authors as cancer markers, were not detected.     

A role for clathrin in reassembly of the Golgi apparatus

The Golgi apparatus is a highly dynamic organelle whose organization is maintained by a proteinaceous matrix, cytoskeletal components, and inositol phospholipids. In mammalian cells, disassembly of the organelle occurs reversibly at the onset of mitosis and irreversibly during apoptosis. Several pharmacological agents including nocodazole, brefeldin A (BFA), and primary alcohols (1-butanol) induce reversible fragmentation of the Golgi apparatus. To dissect the mechanism of Golgi reassembly, rat NRK and GH3 cells were treated with 1-butanol, BFA, or nocodazole. During washout of 1-butanol, clathrin, a ubiquitous coat protein implicated in vesicle traffic at the trans-Golgi network and plasma membrane, and abundant clathrin coated vesicles were recruited to the region of nascent Golgi cisternae. Knockdown of endogenous clathrin heavy chain showed that the Golgi apparatus failed to reform efficiently after BFA or 1-butanol removal. Instead, upon 1-butanol washout, it maintained a compact, tight morphology. Our results suggest that clathrin is required to reassemble fragmented Golgi elements. In addition, we show that after butanol treatment the Golgi apparatus reforms via an initial compact intermediate structure that is subsequently remodeled into the characteristic interphase lace-like morphology and that reassembly requires clathrin.     

Introduction of axial chirality in a planar aromatic ligand results in chiral recognition with DNA

Dimerization of a hydroxycarbazole produces an axially chiral biaryl, BICOL ( 2 ). One enantiomer (R)‐ 2 , is capable of enantioselective binding to different polymorphs of DNA. The biaryl (R)‐ 2 was shown by fluorescence and circular dichroism to induce a shift of Z‐DNA to B‐DNA. The opposite enantiomer (S)‐ 2 shows no specific binding. The significant difference in behaviour between the two enantiomers (S)‐ 2 and (R)‐ 2 is in line with molecular modelling studies which show two very different binding geometries between the enantiomers with each polymorph of DNA. Copyright © 2010 John Wiley & Sons, Ltd.     

Involvement of Saccharomyces cerevisiae Pdr5p ATP-binding cassette transporter in calcium homeostasis

Deletion of PDR5 gene (Deltapdr5) in Saccharomyces cerevisiae led to increased resistance to calcium. The cellular Ca2+ level in the presence of high calcium as estimated by reporter assay in Deltapdr5 cells was significantly lower than that in wild-type cells. Membrane Pdr5p levels diminished rapidly during incubation with high calcium in a manner dependent on calcineurin and Pep4p, suggesting a feedback regulatory mechanism for Pdr5p abundance.     

The devil in the details: the emerging role of anticitrulline autoimmunity in rheumatoid arthritis

Rheumatoid arthritis is a chronic inflammatory autoimmune disease of unknown cause. The immune response against citrullinated Ags has recently become the prime suspect for disease pathogenesis. Immunity against citrullinated Ags is thought to play a pivotal role in the disease for several reasons: 1) citrullinated Ags are expressed in the target organ, the inflamed joint; 2) anti-citrullinated protein Abs are present before the disease becomes manifest; and 3) these Abs are highly specific for rheumatoid arthritis. In this review, data from clinical, genetic, biochemical, and animal studies is combined to create a profile of this remarkable autoantibody response. Moreover, a model is proposed of how the anti-citrullinated proteins response is generated and how it could eventually lead to chronic inflammation.     

Residues in the hendra virus fusion protein transmembrane domain are critical for endocytic recycling

Hendra virus is a highly pathogenic paramyxovirus classified as a biosafety level four agent. The fusion (F) protein of Hendra virus is critical for promoting viral entry and cell-to-cell fusion. To be fusogenically active, Hendra virus F must undergo endocytic recycling and cleavage by the endosomal/lysosomal protease cathepsin L, but the route of Hendra virus F following internalization and the recycling signals involved are poorly understood. We examined the intracellular distribution of Hendra virus F following endocytosis and showed that it is primarily present in Rab5- and Rab4-positive endosomal compartments, suggesting that cathepsin L cleavage occurs in early endosomes. Hendra virus F transmembrane domain (TMD) residues S490 and Y498 were found to be important for correct Hendra virus F recycling, with the hydroxyl group of S490 and the aromatic ring of Y498 important for this process. In addition, changes in association of isolated Hendra virus F TMDs correlated with alterations to Hendra virus F recycling, suggesting that appropriate TMD interactions play an important role in endocytic trafficking.     

Caloric restriction may reverse age-related autonomic decline in humans

Caloric restriction (CR) retards aging in laboratory rodents. No information is available on the effects of long-term CR on physiologic markers of aging and longevity in humans. Heart rate variability (HRV) is a marker for cardiac autonomic functioning. The progressive decline in HRV with aging and the association of higher HRV with better health outcomes are well established. Heart rate variability assessment is a reliable tool by which the effects of CR on autonomic function can be assessed. Time- and frequency-domain analyses compared 24-h HRV in 22 CR individuals aged 35-82 years and 20 age-matched controls eating Western diets (WD). The CR group was significantly leaner than the WD group. Heart rate was significantly lower, and virtually, all HRV values were significantly higher in the CR group than in the WD group (P < 0.002). Heart rate variability in the CR individuals was comparable with published norms for healthy individuals 20 years younger. In addition, when differences in heart rate (HR) and HRV between CR and WD were compared with previously published changes in HRV induced in healthy adults given atenolol, percent differences in each measure were generally similar in direction and magnitude and suggested declines in sympathetic and increases in parasympathetic modulation of HR and increased circadian variability associated with CR. These findings provide evidence that CR has direct systemic effects that counter the expected age-associated changes in autonomic function so that HRV indexes in CR individuals are similar to those of individuals 20 years younger eating WDs.     

Measurements of the cross-bridge attachment/detachment process within intact sarcomeres by surface plasmon resonance.

We have developed a surface plasmon resonance (SPR) system to monitor the cross-bridge attachment/detachment process within intact sarcomeres from mouse heart muscle. SPR occurs when laser light energy is transferred to surface plasmons that are resonantly excited in a metal (gold) film. This resonance manifests itself as a minimum in the reflection of the incident laser light and occurs at a characteristic angle. The angle of the SPR occurrence depends on the dielectric permittivity of the sample medium adjacent to the gold film. Purified sarcomeric preparations are immobilized onto the gold film in the presence of a relaxing solution. Replacement of the relaxing solution with increasing Ca(2+) concentration solution activates the cross-bridge interaction and produces an increase in the SPR angle. These results imply that the interaction of myosin heads with actin within an intact sarcomere changes the dielectric permittivity of the sarcomeric structure. In addition, we further verify that SPR measurements can detect the changes in the population of the attached cross-bridges with altered concentrations of phosphate, 2,3-butanedione monoxime, or adenosine triphosphate at a fixed calcium concentration, which have been shown to reduce the force and increase the cross-bridge population in attached state. Thus, our data provide the first evidence that the SPR technique allows the monitoring of the cross-bridge attachment/detachment process within intact sarcomeres.