Neurogranin modulates the rate of association between calmodulin and target peptides.

The best-known mode of action of calmodulin (CaM) is binding of Ca to its N- and C-domains, followed by binding to target proteins. An underappreciated facet of this process is that CaM is typically bound to proteins at basal levels of free Ca, including the small, intrinsically disordered, neuronal IQ-motif proteins called PEP-19 and neurogranin (Ng). PEP-19 and Ng would not be effective competitive inhibitors of high-affinity Ca-dependent CaM targets at equilibrium because they bind to CaM with relatively low affinity, but they could influence the time course of CaM signaling by affecting the rate of association of CaM with high-affinity Ca-dependent targets.

Bi-directional allosteric pathway in NMDA receptor activation and modulation.

N-methyl-D-aspartate (NMDA) receptors are ionotropic glutamate receptors involved in learning and memory. NMDA receptors primarily comprise two GluN1 and two GluN2 subunits. The GluN2 subunit dictates biophysical receptor properties, including the extent of receptor activation and desensitization.

Neurogranin modulates the Rate of Association between Calmodulin and Target Peptides.

Unlabelled: The best-known mode of action of calmodulin (CaM) is binding of Ca to its N- and C-domains, followed by binding to target proteins. An underappreciated facet of this process is that CaM is typically bound to proteins at basal levels of free Ca , including the small, intrinsically disordered, neuronal IQ-motif proteins called PEP-19 and neurogranin (Ng). PEP-19 and Ng would not be effective competitive inhibitors of high-affinity Ca -dependent CaM targets at equilibrium since they bind to CaM with relatively low affinity, but they could influence the time course of CaM signaling by affecting the rate of association of CaM with high-affinity Ca -dependent targets.

High-Throughput Microbore LC-MS Lipidomics to Investigate APOE Phenotypes.

Microflow liquid chromatography interfaced with mass spectrometry (μLC-MS/MS) is increasingly applied for high-throughput profiling of biological samples and has been proven to have an acceptable trade-off between sensitivity and reproducibility. However, lipidomics applications are scarce. We optimized a μLC-MS/MS system utilizing a 1 mm inner diameter × 100 mm column coupled to a triple quadrupole mass spectrometer to establish a sensitive, high-throughput, and robust single-shot lipidomics workflow.

Examination of 'high-energy' metastable state of the oxidized (O) bovine cytochrome c oxidase: Proton uptake and reaction with HO.

Reoxidized cytochrome c oxidase appears to be in a 'high-energy' metastable state (O) in which part of the energy released in the redox reactions is stored. The O is supposed to relax to the resting 'as purified' oxidized state (O) in a time exceeding 200 ms. The catalytic heme a-Cu center of these two forms should differ in a protonation and ligation state and the transition of O-to-O is suggested to be associated with a proton transfer into this center.

Partial agonism in heteromeric GLUK2/GLUK5 kainate receptor.

Kainate receptors are a subtype of ionotropic glutamate receptors that form transmembrane channels upon binding glutamate. Here, we have investigated the mechanism of partial agonism in heteromeric GluK2/K5 receptors, where the GluK2 and GluK5 subunits have distinct agonist binding profiles. Using single-molecule Förster resonance energy transfer, we found that at the bi-lobed agonist-binding domain, the partial agonist AMPA-bound receptor occupied intermediate cleft closure conformational states at the GluK2 cleft, compared to the more open cleft conformations in apo form and more closed cleft conformations in the full agonist glutamate-bound form.

Gating intermediates reveal inhibitory role of the voltage sensor in a cyclic nucleotide-modulated ion channel.

Understanding how ion channels gate is important for elucidating their physiological roles and targeting them in pathophysiological states. Here, we used SthK, a cyclic nucleotide-modulated channel from Spirochaeta thermophila, to define a ligand-gating trajectory that includes multiple on-pathway intermediates. cAMP is a poor partial agonist for SthK and depolarization increases SthK activity.

Delta glutamate receptors are functional glycine- and ᴅ-serine-gated cation channels in situ.

Delta receptors are members of the ionotropic glutamate receptor superfamily and form trans-synaptic connections by interacting with the extracellular scaffolding protein cerebellin-1 and presynaptic transmembrane protein neurexin-1β. Unlike other family members, however, direct agonist-gated ion channel activity has not been recorded in delta receptors. Here, we show that the GluD2 subtype of delta receptor forms cation-selective channels when bound to cerebellin-1 and neurexin-1β.

Characterization of Individualized Glycemic Excursions during a Standardized Bout of Hypoglycemia-Inducing Exercise and Subsequent Hypoglycemia Treatment-A Pilot Study.

The glycemic response to ingested glucose for the treatment of hypoglycemia following exercise in type 1 diabetes patients has never been studied. Therefore, we aimed to characterize glucose dynamics during a standardized bout of hypoglycemia-inducing exercise and the subsequent hypoglycemia treatment with the oral ingestion of glucose. Ten male patients with type 1 diabetes performed a standardized bout of cycling exercise using an electrically braked ergometer at a target heart rate (THR) of 50% of the individual heart rate reserve, determined using the Karvonen equation.

Structural Arrangement Produced by Concanavalin A Binding to Homomeric GluK2 Receptors.

Kainate receptors are members of the ionotropic glutamate receptor family. They form cation-specific transmembrane channels upon binding glutamate that desensitize in the continued presence of agonists. Concanavalin A (Con-A), a lectin, stabilizes the active open-channel state of the kainate receptor and reduces the extent of desensitization.

Regional differences in presentation characteristics, use of treatments and outcome of patients with cardiogenic shock: Results from multicenter, international registry.

Background: Concurrent evidence about cardiogenic shock (CS) characteristics, treatment and outcome does not represent a global spectrum of patients and is therefore limited. The aim of this study was to investigate these regional differences.

Methods: To investigate regional differences in presentation characteristics, treatments and outcomes of patients treated with all types of cardiogenic shock (CS) in a single calendar year on a multi-national level.

A new paradigm for gaseous ligand selectivity of hemoproteins highlighted by soluble guanylate cyclase.

Nitric oxide (NO), carbon monoxide (CO), and oxygen (O) are important physiological messengers whose concentrations vary in a remarkable range, [NO] typically from nM to several μM while [O] reaching to hundreds of μM. One of the machineries evolved in living organisms for gas sensing is sensor hemoproteins whose conformational change upon gas binding triggers downstream response cascades. The recently proposed "sliding scale rule" hypothesis provides a general interpretation for gaseous ligand selectivity of hemoproteins, identifying five factors that govern gaseous ligand selectivity.

Allosteric Changes in the NMDA Receptor Associated with Calcium-Dependent Inactivation.

N-methyl-D-aspartate (NMDA) receptors mediate synaptic excitatory signaling in the mammalian central nervous system by forming calcium-permeable transmembrane channels upon binding glutamate and coagonist glycine. Ca influx through NMDA receptors leads to channel inactivation through a process mediated by resident calmodulin bound to the intracellular C-terminal segment of the GluN1 subunit of the receptor. Using single-molecule FRET investigations, we show that in the presence of calcium-calmodulin, the distance across the two GluN1 subunits at the entrance of the first transmembrane segment is shorter and the bilobed cleft of the glycine-binding domain in GluN1 is more closed when bound to glycine and glutamate relative to what is observed in the presence of barium-calmodulin.

Mechanism of modulation of AMPA receptors by TARP-γ8.

Fast excitatory synaptic transmission in the mammalian central nervous system is mediated by glutamate-activated α-amino-5-methyl-3-hydroxy-4-isoxazole propionate (AMPA) receptors. In neurons, AMPA receptors coassemble with transmembrane AMPA receptor regulatory proteins (TARPs). Assembly with TARP γ8 alters the biophysical properties of the receptor, producing resensitization currents in the continued presence of glutamate.

Critical Comparison of the Superoxide Dismutase-like Activity of Carbon Antioxidant Nanozymes by Direct Superoxide Consumption Kinetic Measurements.

The superoxide dismutase-like activity of poly(ethylene glycolated) hydrophilic carbon clusters (PEG-HCCs), anthracite and bituminous graphene quantum dots (PEG-aGQDs and PEG-bGQDs, respectively), and two fullerene carbon nanozymes, tris malonyl-C fullerene (C3) and polyhydroxylated-C fullerene (C-OH), were compared using direct optical stopped-flow kinetic measurements, together with three native superoxide dismutases (SODs), CuZnSOD, MnSOD, and FeSOD, at both pH 12.7 and 8.5.

The structural arrangement and dynamics of the heteromeric GluK2/GluK5 kainate receptor as determined by smFRET.

Kainate receptors, which are glutamate activated excitatory neurotransmitter receptors, predominantly exist as heteromers of GluK2 and GluK5 subunits in the mammalian central nervous system. There are currently no structures of the full-length heteromeric kainate receptors. Here, we have used single molecule FRET to determine the specific arrangement of the GluK2 and GluK5 subunits within the dimer of dimers configuration in a full-length receptor.

The structural arrangement at intersubunit interfaces in homomeric kainate receptors.

Kainate receptors are glutamate-gated cation-selective channels involved in excitatory synaptic signaling and are known to be modulated by ions. Prior functional and structural studies suggest that the dimer interface at the agonist-binding domain plays a key role in activation, desensitization, and ion modulation in kainate receptors. Here we have used fluorescence-based methods to investigate the changes and conformational heterogeneity at these interfaces associated with the resting, antagonist-bound, active, desensitized, and ion-modulated states of the receptor.

Highly Oxidized Graphene Quantum Dots from Coal as Efficient Antioxidants.

Graphene quantum dots (GQDs) have recently been employed in various fields including medicine as antioxidants, primarily because of favorable biocompatibility in comparison to common inorganic quantum dots, although the structural features that lead to the biological activities of GQDs are poorly understood. Here, we report that coal-derived GQDs and their poly(ethylene glycol)-functionalized derivatives serve as efficient antioxidants, and we evaluate their electrochemical, chemical, and in vitro biological activities.

Efficacy of Novel Carbon Nanoparticle Antioxidant Therapy in a Severe Model of Reversible Middle Cerebral Artery Stroke in Acutely Hyperglycemic Rats.

Introduction: While oxidative stress can be measured during transient cerebral ischemia, antioxidant therapies for ischemic stroke have been clinically unsuccessful. Many antioxidants are limited in their range and/or capacity for quenching radicals and can generate toxic intermediates overwhelming depleted endogenous protection. We developed a new antioxidant class, 40 nm × 2 nm carbon nanoparticles, hydrophilic carbon clusters, conjugated to poly(ethylene glycol) termed PEG-HCCs.

Structural and Functional Insight of Sphingosine 1-Phosphate-Mediated Pathogenic Metabolic Reprogramming in Sickle Cell Disease.

Elevated sphingosine 1-phosphate (S1P) is detrimental in Sickle Cell Disease (SCD), but the mechanistic basis remains obscure. Here, we report that increased erythrocyte S1P binds to deoxygenated sickle Hb (deoxyHbS), facilitates deoxyHbS anchoring to the membrane, induces release of membrane-bound glycolytic enzymes and in turn switches glucose flux towards glycolysis relative to the pentose phosphate pathway (PPP). Suppressed PPP causes compromised glutathione homeostasis and increased oxidative stress, while enhanced glycolysis induces production of 2,3-bisphosphoglycerate (2,3-BPG) and thus increases deoxyHbS polymerization, sickling, hemolysis and disease progression.

Gaseous ligand selectivity of the H-NOX sensor protein from Shewanella oneidensis and comparison to those of other bacterial H-NOXs and soluble guanylyl cyclase.

To delineate the commonalities and differences in gaseous ligand discrimination among the heme-based sensors with Heme Nitric oxide/OXygen binding protein (H-NOX) scaffold, the binding kinetic parameters for gaseous ligands NO, CO, and O, including K, k, and k, of Shewanella oneidensis H-NOX (So H-NOX) were characterized in detail in this study and compared to those of previously characterized H-NOXs from Clostridium botulinum (Cb H-NOX), Nostoc sp. (Ns H-NOX), Thermoanaerobacter tengcongensis (Tt H-NOX), Vibrio cholera (Vc H-NOX), and human soluble guanylyl cyclase (sGC), an H-NOX analogue. The K(NO) and K(CO) of each bacterial H-NOX or sGC follow the "sliding scale rule"; the affinities of the bacterial H-NOXs for NO and CO vary in a small range but stronger than those of sGC by at least two orders of magnitude.

Perylene Diimide as a Precise Graphene-like Superoxide Dismutase Mimetic.

Here we show that the active portion of a graphitic nanoparticle can be mimicked by a perylene diimide (PDI) to explain the otherwise elusive biological and electrocatalytic activity of the nanoparticle construct. Development of molecular analogues that mimic the antioxidant properties of oxidized graphenes, in this case the poly(ethylene glycolated) hydrophilic carbon clusters (PEG-HCCs), will afford important insights into the highly efficient activity of PEG-HCCs and their graphitic analogues. PEGylated perylene diimides (PEG-PDI) serve as well-defined molecular analogues of PEG-HCCs and oxidized graphenes in general, and their antioxidant and superoxide dismutase-like (SOD-like) properties were studied.