Subcellular distribution of the enzymes of the malate-aspartate shuttle in rat heart and effect of experimental cardiac hypertrophy

The effect of experimental cardiac hypertrophy on the enzymes of the malate - aspartate shuttle aspartate aminotransferase (AAT) and malate dehydrogenase (MDH) was studied. ( l ) Aortic constriction in adult rats resulted in 25% cardiac hypertrophy in 2 1/2-3 weeks. Total DNA (mg per heart) did not change. ( 2 ) The proportions of mitochondrial and cytosolic isozymes of AAT and MDH did not change as a result of cardiac h y p e r t r o p h y . About two-thirds of each enzyme occurred in the mitochondrial form and one-third in the cytosolic form. ( 3 ) Total AAT in hypertrophic hearts, in enzyme units per mg DNA, increased by 24% compared to AAT content in the hearts of sham-operated animals . Total MDH did not change. SoIubilized protein increased by 20%. Normal hearts contained 10 times more enzyme units of MDH than of AAT. (4) Cardiac growth stimulation induced in newborn rats did not result in specific changes of either enzyme. It is suggested that true cardiac hypertrophy acts as a specific stimulus for the possibly rate-limiting enzyme AAT of the shuttle.     

A highly sensitive molecular structural probe applied to in situ biosensing of metabolites using PEDOT:PSS

A large amount of research within organic biosensors is dominated by organic electrochemical transistors (OECTs) that use conducting polymers such as poly(3,4-ethylene dioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS). Despite the recent advances in OECT-based biosensors, the sensing is solely reliant on the amperometric detection of the bioanalytes. This is typically accompanied by large undesirable parasitic electrical signals from the electroactive components in the electrolyte. Herein, we present the use of in situ resonance Raman spectroscopy to probe subtle molecular structural changes of PEDOT:PSS associated with its doping level. We demonstrate how such doping level changes of PEDOT:PSS can be used, for the first time, on operational OECTs for sensitive and selective metabolite sensing while simultaneously performing amperometric detection of the analyte. We test the sensitivity by molecularly sensing a lowest glucose concentration of 0.02 mM in phosphate-buffered saline solution. By changing the electrolyte to cell culture media, the selectivity of in situ resonance Raman spectroscopy is emphasized as it remains unaffected by other electroactive components in the electrolyte. The application of this molecular structural probe highlights the importance of developing biosensing probes that benefit from high sensitivity of the material's structural and electrical properties while being complimentary with the electronic methods of detection.     

Conformational study of new amphipathic alpha-helical peptide models of apoA-I as potential atheroprotective agents

Aiming at contributing to the development of potential atheroprotective agents, we report on the concept and design of two peptide models, which mimic the amphipathic helices of apoA-I and incorporate Met into their sequences to validate its role as oxidant scavenger: Ac-ESK(Palm)KELSKSW(10)SEM(13)LKEK(Palm)SKS-NH(2) (model 1 [W(10), M(13)]) and Ac-ESK(Palm)KELSKSM(10)SEW(13)LKEK(Palm)SKS-NH(2) (model 2 [M(10), W(13)]). Hydrophobic residues of both models cover about the half of the surface, while the positively and negatively charged residues constitute two separate clusters on the hydrophilic face. Palmitoyl groups were introduced into the Lys-N(epsilon)H(2) groups at positions 3 and 17 to contribute to the amphipathic character of the peptides and stabilize the nonpolar face of the helix. Conformational study by the combined application of 2D-NMR and molecular dynamics simulations, CD, FTIR, and fluorescence spectroscopy revealed that model 1 adopts helical conformation and Met is well exposed to the microenvironment. Model 2 that derives from model 1 by exchanging W(10) (model 1) with M(10) and M(13) (model 1) with W(13) also displays helical characteristics, while Met is rather shielded. Oxidation experiments indicated that model 1 exhibits a 2-fold more potent antioxidant activity towards LDL oxidation, compared to model 2, confirming the role of Met, when is devoid of steric hindrances, as oxidant scavenger for the protection of LDL.     

Genetic skeletal disorders of the fetus and infant: Pathologic and molecular findings in a series of 41 cases

BACKGROUND: Genetic skeletal disorders of the fetus and infant are a large group of genetic disorders, comprising the groups formerly assigned as skeletal dysplasias (osteochondrodysplasias), dysostoses, and malformation syndromes with a skeletal component. Genetic skeletal disorders may be prenatally detected by ultrasonography or result in intrauterine or early postnatal death, constituting one difficult diagnostic field met by the pathologist who performs the perinatal autopsy. METHODS: In this retrospective study, we have gathered radiologic, physical, histopathologic, and molecular data regarding 41 cases of genetic skeletal disorders diagnosed among 1980 fetal and perinatal autopsies over a 10‐year period. RESULTS: Our series of cases were classified according to the 2006 Nosology and Classification of Genetic Skeletal Disorders. The overall frequency of genetic skeletal disorders was 1:48 autopsies. The FGFR3 group and osteogenesis imperfecta type 2 were the more frequently encountered disorders. The mean gestational age at autopsy was 21.9 weeks (range, 12–37 weeks). A final diagnosis was obtained in 95% of cases. Genetic skeletal disorders were detected by prenatal ultrasound in 90% of cases, with a correct typing of the disorder achieved in only 34%. Molecular analysis was confirmative in 5 cases. CONCLUSIONS: The central role of the perinatal pathologist in collaboration with specialized services is essential for the correct interpretation of the radiologic, physical, and histopathologic findings, to accurately classify specific types of genetic skeletal disorders and enable genetic counseling. Birth Defects Research (Part A), 2009. © 2009 Wiley‐Liss, Inc.     

Effects of the new adiponectin paralogous protein CTRP-3 and of LPS on cytokine release from monocytes of patients with type 2 diabetes mellitus

Aims/Hypothesis: It was the aim to investigate the hypothesis that the new C1q/TNF-family member CTRP-3 (C1q/TNF-related protein-3) acts anti-inflammatory in human monocytes from healthy controls and patients with type 2 diabetes mellitus (T2D). Methods: Monocytes were isolated from 20 healthy controls and 30 patients with T2D. IL-6 and TNF concentrations were measured by ELISA. CTRP-3 was expressed in insect cells and used for stimulation experiments. Results: Basal IL-6 and TNF were not different in control and in T2D monocytes. LPS-stimulation (1 μg/ml) significantly (p < 0.001) increased IL-6 and TNF in the supernatants of control and in T2D monocytes to a similar extent. CTRP-3 (1 μg/ml) significantly (p = 0.03) inhibited LPS-induced IL-6 in control monocytes but not in T2D monocytes. TNF upon co-stimulation with LPS and CTRP-3 was significantly (p = 0.012) lower in control than in T2D monocytes. LPS-induced TNF concentration was significantly and positively correlated with serum total cholesterol and LDL cholesterol in T2D patients. Conclusions: CTRP-3 inhibits LPS-induced IL-6 and TNF release. This anti-inflammatory effect is lost in T2D. Serum cholesterol concentration affects the pro-inflammatory potential of LPS to induce TNF release from T2D monocytes in the presence or absence of CTRP-3. CTRP-3 might partly account for the pro-inflammatory state in T2D.     

E-LDL upregulates TOSO expression and enhances the survival of human macrophages

Uptake of modified lipoproteins by macrophages causes foam cell formation and promotes atherosclerosis. Atherogenic lipoproteins are cytotoxic and induce cell death under certain conditions but may also enhance macrophage survival. Macrophages treated with enzymatically modified LDL (E-LDL) were subjected to GeneChip analysis and the antiapoptotic gene TOSO was found induced. TOSO mRNA is upregulated and apoptosis is reduced in E-LDL but not in oxidized LDL (Ox-LDL) loaded macrophages. FLIP(L) abundance was suggested to mediate the antiapoptotic properties of TOSO; however, FLIP(L) was not changed. Ox-LDL is internalized predominantly by scavenger receptors such as CD36 while E-LDL particles are preferentially internalized by Fc- and complement-receptor dependent phagocytosis and internalization of phagobeads by macrophages upregulates TOSO. In COS-7 cells however, phagocytotic activity was not affected by TOSO. These data indicate that E-LDL-generated foam cells are protected from cell death most likely through the expression of TOSO by a FLIP(L) independent mechanism.     

Protein dynamics and allostery: an NMR view

Allostery, the process by which distant sites within a protein system are energetically coupled, is an efficient and ubiquitous mechanism for activity regulation. A purely mechanical view of allostery invoking only structural changes has developed over the decades as the classical view of the phenomenon. However, a fast growing list of examples illustrate the intimate link between internal motions over a wide range of time scales and function in protein-ligand interactions. Proteins respond to perturbations by redistributing their motions and they use fluctuating conformational states for binding and conformational entropy as a carrier of allosteric energy to modulate association with ligands. In several cases allosteric interactions proceed with minimal or no structural changes. We discuss emerging paradigms for the central role of protein dynamics in allostery.     

NMR reveals novel mechanisms of protein activity regulation

NMR spectroscopy is one of the most powerful tools for the characterization of biomolecular systems. A unique aspect of NMR is its capacity to provide an integrated insight into both the structure and intrinsic dynamics of biomolecules. In addition, NMR can provide site-resolved information about the conformation entropy of binding, as well as about energetically excited conformational states. Recent advances have enabled the application of NMR for the characterization of supramolecular systems. A summary of mechanisms underpinning protein activity regulation revealed by the application of NMR spectroscopy in a number of biological systems studied in the lab is provided.     

Structural basis for regulation of the Crk signaling protein by a proline switch

Proline switches, controlled by cis-trans isomerization, have emerged as a particularly effective regulatory mechanism in a wide range of biological processes. Here we report the structures of both the cis and trans conformers of a proline switch in the Crk signaling protein. Proline isomerization toggles Crk between two conformations: an autoinhibitory conformation, stabilized by the intramolecular association of two tandem SH3 domains in the cis form, and an uninhibited, activated conformation promoted by the trans form. In addition to acting as a structural switch, the heterogeneous proline recruits cyclophilin A, which accelerates the interconversion rate between the isomers, thereby regulating the kinetics of Crk activation. The data provide atomic insight into the mechanisms that underpin the functionality of this binary switch and elucidate its remarkable efficiency. The results also reveal new SH3 binding surfaces, highlighting the binding versatility and expanding the noncanonical ligand repertoire of this important signaling domain.