Phospholipase D stimulation by receptor tyrosine kinases mediated by protein kinase C and a Ras/Ral signaling cascade

Stimulation of phospholipase D (PLD) in HEK-293 cells expressing the M(3) muscarinic receptor by phorbol ester-activated protein kinase C (PKC) apparently involves Ral GTPases. We report here that PKC, but not muscarinic receptor-induced PLD stimulation in these cells, is strongly and specifically reduced by expression of dominant-negative RalA, G26A RalA, as well as dominant-negative Ras, S17N Ras. In contrast, overexpression of the Ras-activated Ral-specific guanine nucleotide exchange factor, Ral-GDS, specifically enhanced PKC-induced PLD stimulation. Moreover, recombinant Ral-GDS potentiated Ral-dependent PKC-induced PLD stimulation in membranes. Epidermal growth factor, platelet-derived growth factor, and insulin, ligands for receptor tyrosine kinases (RTKs) endogenously expressed in HEK-293 cells, apparently use the PKC- and Ras/Ral-dependent pathway for PLD stimulation. First, PLD stimulation by the RTK agonists was prevented by PKC inhibition and PKC down-regulation. Second, expression of dominant-negative RalA and Ras mutants strongly reduced RTK-induced PLD stimulation. Third, overexpression of Ral-GDS largely potentiated PLD stimulation by the RTK agonists. Finally, using the Ral binding domain of the Ral effector RLIP as an activation-specific probe for Ral proteins, it is demonstrated that endogenous RalA is activated by phorbol ester and RTK agonists. Taken together, strong evidence is provided that RTK-induced PLD stimulation in HEK-293 cells is mediated by PKC and a Ras/Ral signaling cascade.     

Engineered mutations change the structure and stability of a virus-like particle

The single-coat protein (CP) of bacteriophage Qβ self-assembles into T = 3 icosahedral virus-like particles (VLPs), of interest for a wide range of applications. These VLPs are very stable, but identification of the specific molecular determinants of this stability is lacking. To investigate these determinants along with manipulations that confer more capabilities to our VLP material, we manipulated the CP primary structure to test the importance of various putative stabilizing interactions. Optimization of a procedure to incorporate fused CP subunits allowed for good control over the average number of covalent dimers in each VLP. We confirmed that the disulfide linkages are the most important stabilizing elements for the capsid and that acidic conditions significantly enhance the resistance of VLPs to thermal degradation. Interdimer interactions were found to be less important for VLP assembly than intradimer interactions. Finally, a single point mutation in the CP resulted in a population of smaller VLPs in three distinct structural forms.     

Glatiramer Acetate Increases Phagocytic Activity of Human Monocytes In Vitro and in Multiple Sclerosis Patients

Beside its effects on T cells, a direct influence on cells of the myelo-monocytic lineage by GA becomes evident. Recently, we demonstrated that GA drives microglia to adopt properties of type II antigen presenting cells (APC) and increases their phagocytic activity. In the present work, we focused on human blood monocytes in order to examine whether GA may increase phagocytic activity in vivo and to evaluate the molecular mechanisms explaining this new discovered mode of action. Peripheral blood mononuclear cells (PBMC) were obtained using a Biocoll-Isopaque gradient and monocytes were subsequently isolated by using CD14 MicroBeads. Phagocytic activity was determined by flow cytometric measurement of the ingestion of fluorescent beads. Flow cytometry was also used to assess monocytic differentiation and expression of phagocytic receptors. Monocytes of GA treated MS patients exhibited a significantly higher phagocytic activity than those of healthy controls or non-treated MS patients. In vitro, a significant phagocytic response was already detectable after 1 h of GA treatment at the concentrations of 62.5 and 125 µg/ml. A significant increase at all concentrations of GA was observed after 3 h and 24 h, respectively. Only monocytes co-expressing CD16, particularly CD14⁺⁺CD16⁺ cells, were observed to phagocytose. Treatment of monocytes with IL-10 and supernatants from GA-treated monocytes did not alter phagocytosis. We observed a decrease in CD11c expression by GA while no changes were found in the expression of CD11b, CD36, CD51/61, CD91, TIM-3, and CD206. In our blocking assays, treatment with anti-CD14, anti-CD16, anti-TIM3, anti-CD210, and particularly anti-CD36 antibodies led to a decrease in phagocytosis. Our results demonstrate a new mechanism of action of GA treatment that augments phagocytic activity of human monocytes in vivo and in vitro. This activity seems to arise from the CD14⁺⁺CD16⁺ monocyte subset.     

Histological studies on cultured canine heart valves recovered from −196 °C

Adult canine heart valves have been frozen to ?196 °C, (0.5 to 0.7 °C/min from 0 to ?100 °C) with 10% DMSO ($\text{v}\text{v}$), stored, thawed at ~150 °C/min, and then cultured for 9 to 12 days. A histological analysis of sections derived from several valves indicates viability, but with a not inconsiderable loss of stromal fibrocytes and some damage to the endothelial lining. The practicality of freezing valve tissue for banking will have to be looked at critically, before valve transplants can be considered as a possible alternative to the well established use of mechanical valve prosthesis. However, demonstrating viability of heart valve tissue extends the range of tissues that are amenable to cryopreservation.     

C-terminal interactions of apolipoprotein E4 respond to the postprandial state

Increased triglyceride-rich lipoproteins (TGRLs) in the postprandial state are associated with atherosclerosis. We investigated whether the postprandial state induced structural changes at the apolipoprotein E4 (apoE4) C terminus, its principal lipid binding domain, using electron paramagnetic resonance (EPR) spectroscopy of a site-directed spin label attached to the cysteine of apoE4-W264C. Spin coupling between labels located in the C termini was followed after mixing with preprandial and postprandial human plasma samples. Our results indicate that postprandial plasma triggers a reorganization of the protein such that the dipolar broadening is diminished, indicating a reduction in C-terminal interaction. The loss of spectral broadening was directly correlated with an increase in postprandial plasma triglycerides and was reduced with delipidated plasma. The spin-labeled apoE4 displayed a lipid preference of VLDL > LDL > HDL in the preprandial and postprandial states. The apoE4 shift to VLDL during the postprandial state was accompanied by a loss in spectral broadening of the protein. These findings suggest that apoE4 associated with LDL maintains self-association via its C terminus and that this association is diminished in VLDL-associated protein. Lipolyzed TGRL reflected a depletion of the C-terminal interaction of apoE4. Addition of palmitate to VLDL gave a similar response as lipolyzed TGRL, suggesting that lipolysis products play a major role in reorganizing apoE4 during the postprandial state.     

Clinical oxidation parameters of aging

Aging is a complex progressive physiological alteration of the organism which ultimately leads to death. During the whole life a human being is confronted with oxidative stress. To measure how this oxidative stress is developing during the aging process and how it changes the cellular metabolism several substances have been pronounced as biomarkers including lipid peroxidation (LPO) products, protein oxidation products, antioxidative acting enzymes, minerals, vitamins, glutathione, flavonoids, bilirubin and uric acid (UA).

But none of them could develop to the leading one which is accepted by the whole scientific community to determine the life expectancy of the individual person or biological age or age-related health status. Further there are many conflicting data about the changes of each single biomarker during the aging process.

There are so many different influences acting on the concentration or activity of single substances or single enzymes that it is not possible to measure only one clinical marker and determine how healthy an individual is or to predict the life expectancy of the corresponding person. Therefore, always a set or pattern of clinical biomarkers should be used to determine the oxidation status of the person. This set should include at least one marker for the LPO, the protein oxidation and the total antioxidative status and ideally also one for DNA damages.     

N‐cadherin is dispensable for pancreas development but required for β‐cell granule turnover

The cadherin family of cell adhesion molecules mediates adhesive interactions that are required for the formation and maintenance of tissues. Previously, we demonstrated that N‐cadherin, which is required for numerous morphogenetic processes, is expressed in the pancreatic epithelium at E9.5, but later becomes restricted to endocrine aggregates in mice. To study the role of N‐cadherin during pancreas formation and function we generated a tissue‐specific knockout of N‐cadherin in the early pancreatic epithelium by inter‐crossing N‐cadherin‐floxed mice with Pdx1Cre mice. Analysis of pancreas‐specific ablation of N‐cadherin demonstrates that N‐cadherin is dispensable for pancreatic development, but required for β‐cell granule turnover. The number of insulin secretory granules is significantly reduced in N‐cadherin‐deficient β‐cells, and as a consequence insulin secretion is decreased. genesis 48:374–381, 2010. © 2010 Wiley‐Liss, Inc.     

Effects of hydrostatic pressure on a membrane-enveloped virus: high immunogenicity of the pressure-inactivated virus.

A new approach to the preparation of antiviral vaccines relying on the inactivation of the virus particle by hydrostatic pressure is described. The enveloped virus vesicular stomatitis virus was utilized as a model; a pressure of 260 MPa applied for 12 h reduced infectivity by a factor of 10(4), and the antibodies against pressurized material were as effective as those against the intact virus when measured by their neutralization titer. Fluorescence measurements indicate that application of pressure results in perturbations of the particle interactions that permit binding of specific molecular probes. Electron microscopy showed that the membrane of the pressurized virus was partially preserved, presenting the spike pattern of the membrane G protein. Unlike the icosahedral viruses, dissociation into smaller particles was not observed, but a constant change in the morphology was the presence of a bulge in the surface of the pressurized virus, indicating a displacement of the capsid subunits, retained under the lipid and protein membrane.     

Bone morphogenetic protein 1 prodomain specifically binds and regulates signaling by bone morphogenetic proteins 2 and 4

Highly purified fractions of bone extracts capable of inducing ectopic bone formation have been reported to contain peptides corresponding to the mature active regions of the TGF-beta-like bone morphogenetic proteins (BMPs) 2-7, and to the prodomain region of the metalloproteinase BMP1. Co-purification of BMPs 2-7 with BMP1 prodomain sequences through the multiple biochemical steps used in these previous reports has suggested the possibility of interactions between the BMP1 prodomain and BMPs 2-7. Here we demonstrate that the BMP1 prodomain binds BMPs 2 and 4 with high specificity and with a KD of approximately 11 nM, in the physiological range. It is further demonstrated that the BMP1 prodomain is capable of modulating signaling by BMPs 2 and 4 in vitro and in vivo, and that endogenous BMP1 prodomain-BMP4 complexes exist in cell culture media and in tissues.