Rat pancreas actin: purification and characterization

Isolation of rat pancreas actin was performed with three different technics: polymerization-depolymerization method, affinity chromatography on DNase I-Sepharose 4B or ion exchange chromatography on DEAE-cellulose. Inhibition of DNase I activity, localization by SDS polyacrylamide slab gel electrophoresis and presence of microfilaments allowed its identification. Affinity process led us to obtain actin which kept inhibitory activity (30,000 U per mg) on DNase I when using vacuum dialysis. Actin eluted from DEAE-cellulose associated reversibly in 50-70 A microfilaments in the presence of phalloidin, was pure at 95% and had a satisfactory inhibitor activity (77,000 U per mg).     

The Niemann-Pick C1 protein resides in a vesicular compartment linked to retrograde transport of multiple lysosomal cargo

Niemann-Pick C disease (NP-C) is a neurovisceral lysosomal storage disorder. A variety of studies have highlighted defective sterol trafficking from lysosomes in NP-C cells. However, the heterogeneous nature of additional accumulating metabolites suggests that the cellular lesion may involve a more generalized block in retrograde lysosomal trafficking. Immunocytochemical studies in fibroblasts reveal that the NPC1 gene product resides in a novel set of lysosome-associated membrane protein-2 (LAMP2)(+)/mannose 6-phosphate receptor(-) vesicles that can be distinguished from cholesterol-enriched LAMP2(+) lysosomes. Drugs that block sterol transport out of lysosomes also redistribute NPC1 to cholesterol-laden lysosomes. Sterol relocation from lysosomes in cultured human fibroblasts can be blocked at 21 degrees C, consistent with vesicle-mediated transfer. These findings suggest that NPC1(+) vesicles may transiently interact with lysosomes to facilitate sterol relocation. Independent of defective sterol trafficking, NP-C fibroblasts are also deficient in vesicle-mediated clearance of endocytosed [14C]sucrose. Compartmental modeling of the observed [14C]sucrose clearance data targets the trafficking defect caused by mutations in NPC1 to an endocytic compartment proximal to lysosomes. Low density lipoprotein uptake by normal cells retards retrograde transport of [14C]sucrose through this same kinetic compartment, further suggesting that it may contain the sterol-sensing NPC1 protein. We conclude that a distinctive organelle containing NPC1 mediates retrograde lysosomal transport of endocytosed cargo that is not restricted to sterol.     

Are prognostic factors more favorable for breast cancer detected by organized screening than by opportunistic screening or clinical diagnosis? A study in Loire-Atlantique (France)

Purpose: Comparisons of breast cancer characteristics between organized and opportunistic screening have been limited. This study was designed to compare characteristics of cancers detected by either organized or opportunistic screening as well as clinically diagnosed cancers in Loire-Atlantique (a French administrative entity), from 2003 to 2007. Methods: This study is based on data from the population-based Loire-Atlantique Cancer Registry. Stage at diagnosis and prognostic characteristics of carcinomas detected by organized screening were compared, by age-adjusted logistic regressions, to those of cancers detected by opportunistic screening and diagnosed clinically. Analyses were restricted to women aged 50–74 years (the age group targeted by the organized screening program) for the 2003–2007 period. Results: Between 2003 and 2007, 2864 invasive and 400 in situ breast cancer cases were diagnosed in women aged 50–74 years in Loire-Atlantique. Compared to cancers diagnosed clinically, cancers detected by organized screening were more likely to be in situ (13.7% vs. 3.8%), diagnosed at an early stage (74.4% vs. 51.3%), have a low SBR grade (grade 1: 35.4% vs. 18.5%), and be positive for estrogen–progesterone receptors (68.3% vs. 59.0%). The distribution of stage at diagnosis and prognostic characteristics between organized and opportunistic screening were similar. Conclusion: These findings are consistent with the hypothesis that breast cancers are detected early by organized screening. Cancer characteristics were similar between the two screening modes. Estimating the impact of mammography screening on mortality in Loire-Atlantique should be the object of further investigations.     

Pharmacological inhibition of GSK-3 in a guinea pig model of LPS-induced pulmonary inflammation: II. Effects on skeletal muscle atrophy

Background

Chronic obstructive pulmonary disease (COPD) is accompanied by pulmonary inflammation and associated with extra-pulmonary manifestations, including skeletal muscle atrophy. Glycogen synthase kinase-3 (GSK-3) has been implicated in the regulation of muscle protein- and myonuclear turnover; two crucial processes that determine muscle mass. In the present study we investigated the effect of the selective GSK-3 inhibitor SB216763 on muscle mass in a guinea pig model of lipopolysaccharide (LPS)-induced pulmonary inflammation-associated muscle atrophy.

Methods

Guinea pigs were pretreated with either intranasally instilled SB216763 or corresponding vehicle prior to each LPS/saline challenge twice weekly. Pulmonary inflammation was confirmed and indices of muscle mass were determined after 12 weeks. Additionally, cultured skeletal muscle cells were incubated with tumor necrosis factor α (TNF-α) or glucocorticoids (GCs) to model the systemic effects of pulmonary inflammation on myogenesis, in the presence or absence of GSK-3 inhibitors.

Results

Repeated LPS instillation induced muscle atrophy based on muscle weight and muscle fiber cross sectional area. Intriguingly, GSK-3 inhibition using SB216763 prevented the LPS-induced muscle mass decreases and myofiber atrophy. Indices of protein turnover signaling were unaltered in guinea pig muscle. Interestingly, inhibition of myogenesis of cultured muscle cells by TNF-α or synthetic GCs was prevented by GSK-3 inhibitors.

Conclusions

In a guinea pig model of LPS-induced pulmonary inflammation, GSK-3 inhibition prevents skeletal muscle atrophy without affecting pulmonary inflammation. Resistance to inflammation- or GC-induced impairment of myogenic differentiation, imposed by GSK-3 inhibition, suggests that sustained myogenesis may contribute to muscle mass maintenance despite persistent pulmonary inflammation. Collectively, these results warrant further exploration of GSK-3 as a potential novel drug target to prevent or reverse muscle wasting in COPD.     

Engineering the interactions between a plant‐produced HIV antibody and human Fc receptors

Plants can provide a cost‐effective and scalable technology for production of therapeutic monoclonal antibodies, with the potential for precise engineering of glycosylation. Glycan structures in the antibody Fc region influence binding properties to Fc receptors, which opens opportunities for modulation of antibody effector functions. To test the impact of glycosylation in detail, on binding to human Fc receptors, different glycovariants of VRC01, a broadly neutralizing HIV monoclonal antibody, were generated in Nicotiana benthamiana and characterized. These include glycovariants lacking plant characteristic α1,3‐fucose and β1,2‐xylose residues and glycans extended with terminal β1,4‐galactose. Surface plasmon resonance‐based assays were established for kinetic/affinity evaluation of antibody–FcγR interactions, and revealed that antibodies with typical plant glycosylation have a limited capacity to engage FcγRI, FcγRIIa, FcγRIIb and FcγRIIIa; however, the binding characteristics can be restored and even improved with targeted glycoengineering. All plant‐made glycovariants had a slightly reduced affinity to the neonatal Fc receptor (FcRn) compared with HEK cell‐derived antibody. However, this was independent of plant glycosylation, but related to the oxidation status of two methionine residues in the Fc region. This points towards a need for process optimization to control oxidation levels and improve the quality of plant‐produced antibodies.