Cholesterol homeostasis regulated by ABCA1 is critical for retinal ganglion cell survival

Science China Life Sciences - Genome-wide association studies have suggested a link between primary open-angle glaucoma and the function of ABCA1. ABCA1 is a key regulator of cholesterol efflux and...     

Galectin-3 overexpression protects from cell damage and death by influencing mitochondrial homeostasis

Galectins are a family of proteins involved in several cell processes, including their survival and death. Galectin-3 has in particular been described as an anti-apoptotic molecule entangled with a number of subcellular activities including anoikis resistance. In this work we partially address the mechanisms underlying this activity pointing at two key factors in injury progression: the alteration of mitochondrial membrane potential and the formation of reactive oxygen species. Overexpression of galectin-3 appears in fact to exert a protective effect towards both these events. On the basis of these data, we propose a reappraisal of the role of galectin-3 as a regulator of mitochondrial homeostasis.     

DNA damage and cell cycle events implicate cerebellar dentate nucleus neurons as targets of Alzheimer's disease

Background

The low-density lipoprotein receptor related protein 1 (LRP1) has been implicated in Alzheimer's disease (AD) but its signalling has not been fully evaluated. There is good evidence that the cytoplasmic domain of LRP1 is involved in protein-protein interactions, important in the cell biology of LRP1.

Results

We carried out three yeast two-hybrid screens to identify proteins that interact with the cytoplasmic domain of LRP1. The screens included both conventional screens as well as a novel, split-ubiquitin-based screen in which an LRP1 construct was expressed and screened as a transmembrane protein. The split-ubiquitin screen was validated in a screen using full-length amyloid protein precursor (APP), which successfully identified FE65 and FE65L2, as well as novel interactors (Rab3a, Napg, and ubiquitin b). Using both a conventional screen as well as the split-ubiquitin screen, we identified NYGGF4 as a novel LRP1 interactor. The interaction between LRP1 and NYGGF4 was validated using two-hybrid assays, coprecipitation and colocalization in mammalian cells. Mutation analysis demonstrated a specific interaction of NYGGF4 with an NPXY motif that required an intact tyrosine residue. Interestingly, while we confirmed that other LRP1 interactors we identified, including JIP1B and EB-1, were also able to bind to APP, NYGGF4 was unique in that it showed specific binding with LRP1. Expression of NYGGF4 decreased significantly in patients with AD as compared to age-matched controls, and showed decreasing expression with AD disease progression. Examination of Nyggf4 expression in mice with different alleles of the human APOE4 gene showed significant differences in Nyggf4 expression.

Conclusions

These results implicate NYGGF4 as a novel and specific interactor of LRP1. Decreased expression of LRP1 and NYGGF4 over disease, evident with the presence of even moderate numbers of neuritic plaques, suggests that LRP1-NYGGF4 is a system altered early in disease. Genetic and functional studies have implicated both LRP1 and NYGGF4 in obesity and cardiovascular disease and the physical association of these proteins may reflect a common mechanism. This is particularly interesting in light of the dual role of ApoE in both cardiovascular risk and AD. The results support further studies on the functional relationship between NYGGF4 and LRP1.     

Evolution of invertebrate homeostasis: Osmotic and ionic regulation

• 1.1. Homeostasis, or the maintenance of a constant internal environment, in invertebrate organisms decreases the dependence of these organisms on the vagaries of the external environment.
• 2.2. The evolution of physiological processes influencing homeostatic conditions begins with the organism being totally dependent upon the external environment, passing through a series of intermediate stages during which fluctuation in a given internal parameter occur, proceeding finally to a condition where the internal environment is constant and independent of the external environment.
• 3.3. A hypothetical scheme for the possible evolutionary pathway of osmotic and ionic regulation in aquatic invertebrates was developed in an attempt to follow the process of homeostasis in these organisms.
• 4.4. Primitive marine cells developed mechanisms to regulate the ionic composition of the cytoplasm probably in association with the need for volume regulation.
• 5.5. The development of a body wall separated an internal body fluid from the external sea-water and the ionic composition of the body fluids was initially maintained slightly different from that of the sea-water by essentially passive means.
• 6.6. The addition of excretory organs, which arose initially through an inpushing of the body wall, brought about the ability for osmoregulation.
• 7.7. Homeostatic mechanisms must be in place before an organism can move from one environment to another.

     

Metabolic imprinting: critical impact of the perinatal environment on the regulation of energy homeostasis

Epidemiological studies in humans suggest that maternal undernutrition, obesity and diabetes during gestation and lactation can all produce obesity in offspring. Animal models have allowed us to investigate the independent consequences of altering the pre- versus post-natal environments on a variety of metabolic, physiological and neuroendocrine functions as they effect the development in the offspring of obesity, diabetes, hypertension and hyperlipidemia (the 'metabolic syndrome'). During gestation, maternal malnutrition, obesity, type 1 and type 2 diabetes and psychological, immunological and pharmacological stressors can all promote offspring obesity. Normal post-natal nutrition can reduce the adverse impact of some of these pre-natal factors but maternal high-fat diets, diabetes and increased neonatal access to food all enhance the development of obesity and the metabolic syndrome in offspring. The outcome of these perturbations of the perinatal environmental is also highly dependent upon the genetic background of the individual. Those with an obesity-prone genotype are more likely to be affected by factors such as maternal obesity and high-fat diets than are obesity-resistant individuals. Many perinatal manipulations appear to promote offspring obesity by permanently altering the development of central neural pathways, which regulate food intake, energy expenditure and storage. Given their strong neurotrophic properties, either excess or an absence of insulin and leptin during the perinatal period are likely to be effectors of these developmental changes. Because obesity is associated with an increased morbidity and mortality and because of its resistance to treatment, prevention is likely to be the best strategy for stemming the tide of the obesity epidemic. Such prevention should begin in the perinatal period with the identification and avoidance of factors which produce permanent, adverse alterations in neural pathways which control energy homeostasis.     

Osmotic homeostasis and radiosensitivity of NKLy lymphosarcoma cells]

In experiments with cells of ascites NKLy lymphoma differing in ploidy and position in the cell cycle, a study was made of the radiosensitivity, osmotic homeostasis peculiarities and thermoradiation changes in potassium content. It was shown that the resistance of osmotic homeostasis of NKLy cells to thermoradiation correlated with their radioresistance and was maximally displayed in cells at the stage of DNA synthesis.     

Peroxisomes as novel players in cell calcium homeostasis

Ca2+ concentration in peroxisomal matrix ([Ca2+](perox)) has been monitored dynamically in mammalian cells expressing variants of Ca2+-sensitive aequorin specifically targeted to peroxisomes. Upon stimulation with agonists that induce Ca2+ release from intracellular stores, peroxisomes transiently take up Ca2+ reaching peak values in the lumen as high as 50-100 microm, depending on cell types. Also in resting cells, peroxisomes sustain a Ca2+ gradient, [Ca2+](perox) being approximately 20-fold higher than [Ca2+] in the cytosol ([Ca2+](cyt)). The properties of Ca2+ traffic across the peroxisomal membrane are different from those reported for other subcellular organelles. The sensitivity of peroxisomal Ca2+ uptake to agents dissipating H+ and Na+ gradients unravels the existence of a complex bioenergetic framework including V-ATPase, Ca2+/H+, and Ca2+/Na+ activities whose components are yet to be identified at a molecular level. The different [Ca2+](perox) of resting and stimulated cells suggest that Ca2+ could play an important role in the regulation of peroxisomal metabolism.     

Plant cell walls as targets for biotechnology

Plants are the sources of major food, feed, and fiber products that are used globally. This past year has seen advances in our understanding of the enzymes that modify wall architecture, the cloning of the first cellulose synthase gene, and revisions to the lignin biosynthetic pathway. These discoveries have facilitated the development of new strategies to alter cell wall properties in transgenic plants.     

Exchange of polyamines between the cell and the environment as one of the factors determining the growth of cultures of Escherichia coli with additional feeding

Escherichia coli growth in a synthetic medium with glucose is accompanied by the interdependent change of putrescine content in the cell and its environment, which maintains a homeostatic equilibrium. The rate of putrescine efflux at the early stage of the culture growth is directly proportional to putrescine intracellular pool but the rate of putrescine uptake is inversely proportional to its value. The constitutive form of ornithine decarboxylase with the pH optimum 8.0 is responsible for putrescine synthesis. Glucose deficiency favours the utilisation of acidic glucose metabolites but the homeostatic system of putrescine makes its intracellular content remain at a high level, which stimulates constructive processes in the following growth.     

ZFAT plays critical roles in peripheral T cell homeostasis and its T cell receptor-mediated response

ZFAT, originally identified as a candidate susceptibility gene for autoimmune thyroid disease, has been reported to be involved in apoptosis, development and primitive hematopoiesis. Zfat is highly expressed in T- and B-cells in the lymphoid tissues, however, its physiological function in the immune system remains totally unknown. Here, we generated the T cell-specific Zfat-deficient mice and demonstrated that Zfat-deficiency leads to a remarkable reduction in the number of the peripheral T cells. Intriguingly, a reduced expression of IL-7Rα and the impaired responsiveness to IL-7 for the survival were observed in the Zfat-deficient T cells. Furthermore, a severe defect in proliferation and increased apoptosis in the Zfat-deficient T cells following T cell receptor (TCR) stimulation was observed with a reduced IL-2Rα expression as well as a reduced IL-2 production. Thus, our findings reveal that Zfat is a critical regulator in peripheral T cell homeostasis and its TCR-mediated response.     

Microbial and dietary factors modulating intestinal regulatory T cell homeostasis

To maintain a quiescent gut microenvironment, proper regulation of immune responses initiated by pro-inflammatory immune subsets is required. Several types of regulatory T cells are reported to exert pivotal roles in achieving this. Among various types of regulatory T cells, the crucial role of Foxp3⁺ Treg cells has been well documented. Furthermore, accumulating evidence demonstrates that both microbial and dietary factors influence the induction and suppressor functions of intestinal Foxp3⁺ Treg cells. Foxp3⁺ Treg cells are a highly activated T cell subset which responds rapidly to environmental and nutritional stimuli. Thus, sufficient nutrient supply is required to fuel the high energetic status of Foxp3⁺ Treg cells for the regulation of intestinal immunity.     

Lactate-related factors as a critical determinant of endurance

Many interrelated physiological and/or morphological factors have been demonstrated to influence endurance exercise performance. Some of these factors include skeletal musculature, running economy, maximal oxygen uptake (VO2max), maximal steady state (MSS), onset of blood lactate accumulation (OBLA), onset of plasma lactate accumulation (OPLA), and anaerobic (or lactate) threshold (AT or LT). The present paper focuses mainly on VO2max, MSS, OBLA, OPLA and LT, all of which have been postulated as a prerequisite in endurance exercise success. This paper consists of: (1) significance of La-related variables, (2) longitudinal studies, (3) comments, and (4) conclusion. Briefly, it is suggested that estimation of endurance exercise potential could be obtained with relatively high precision using laboratoriously measured La-related variables. The most critical determinant of endurance exercise performance such as marathon time is considered running velocity (V) at which LT is detected (V / LT), VO2 / LT, or V / MSS, while V / OBLA appears to be the best predictor of performance in endurance events of 16 km or shorter distances.     

Human lymphoid cell lines as targets for DRw

Summary Cultured human lymphoid cell lines (LCL) are useful as a source of target cells in several immunologic assays. More recently such cells have been used for the serological characterizations of the HLA-DR antigens. Typing of the same LCL in various laboratories during the VII Histocompatibility Workshop has given comparable results with a discordancy rate of less than 10%. This discordancy is likely to reflect the different sources of complement that can greatly alter the results of cytotoxic assays. The presence of naturally occuring antibody in rabbit complement to human cells can be avoided by: (a) absorbing with human cells at 0°C; (b) dilution with human serum; (c) dilution with heat-inactivated rabbit serum; (d) repeated freeze-thawing of the complement; or (e) careful selection of complement by screening procedures. Comparison of the results of HLA-DR typing of LCL with peripheral B-cells of the same donor show good correlations. However, LCL will occasionally give extra reactions perhaps due to the expression of new antigens. LCL can be coated with F(ab′)₂ fragments from antihuman β₂-microglobulin antibodies that block reactions of HLA-A, −B and −C antibodies allowing for discrimination of anti-DRw activity. Recipient of an American Heart Established Investigatorship. This work was supported by the Naval Medical Research and Development Command, Work Unit No. ZF51.524.013.1025, and by Grant Nos. AI 13154 AND CA 16071 from the National Institutes of Health.     

Controlled study of critical parent and family factors in the obesigenic environment

Objective: Critical gaps remain in our understanding of the obesigenic family environment. This study examines parent and family characteristics among obese youth presenting for treatment in a clinic setting. Research Methods and Procedures: Families of 78 obese youth (BMI z‐score = 2.4; age, 8 to 16 years; 59% girls; 49% African‐American) were compared with 71 non‐overweight (BMI z‐score = ?0.02) demographically matched comparisons. Parents completed measures assessing family demographics, psychological distress (Symptom Checklist 90‐Revised), and family functioning both broadly (Family Environment Scale: Conflicted, Support, Control) and at mealtimes (About Your Child's Eating‐Revised: Mealtime Challenges, Positive Mealtime Interaction). Height and weight were obtained from all participants. Results: Compared with mothers and fathers of non‐overweight youth, parents of obese youth had significantly higher BMIs (p < 0.001). Mothers of obese youth reported significantly greater psychological distress (p < 0.01), higher family conflict (p < 0.05), and more mealtime challenges (p < 0.01). Less positive family mealtime interactions were reported by both mothers (p < 0.01) and fathers (p < 0.05) of obese youth. These group differences did not vary by child sex or race. Logistic regression analyses indicated that maternal distress and mealtime challenges discriminated between obese and non‐overweight youth after controlling for maternal BMI. Family conflict was explained, in part, by maternal distress. Discussion: Obese youth who present for treatment in a clinic setting are characterized by psychosocial factors at the parent and family level that differ from non‐overweight youth. These data are critical because they identify factors that may be serving as barriers to a family's or youth's ability to implement healthy lifestyle behaviors but that are potentially modifiable.