Mutations in a guanylate cyclase GCY-35/GCY-36 modify Bardet-Biedl syndrome-associated phenotypes in Caenorhabditis elegans

Ciliopathies are pleiotropic and genetically heterogeneous disorders caused by defective development and function of the primary cilium. Bardet-Biedl syndrome (BBS) proteins localize to the base of cilia and undergo intraflagellar transport, and the loss of their functions leads to a multisystemic ciliopathy. Here we report the identification of mutations in guanylate cyclases (GCYs) as modifiers of Caenorhabditis elegans bbs endophenotypes. The loss of GCY-35 or GCY-36 results in suppression of the small body size, developmental delay, and exploration defects exhibited by multiple bbs mutants. Moreover, an effector of cGMP signalling, a cGMP-dependent protein kinase, EGL-4, also modifies bbs mutant defects. We propose that a misregulation of cGMP signalling, which underlies developmental and some behavioural defects of C. elegans bbs mutants, may also contribute to some BBS features in other organisms.     

A biomimetic robotic jellyfish (Robojelly) actuated by shape memory alloy composite actuators

An analysis is conducted on the design, fabrication and performance of an underwater vehicle mimicking the propulsion mechanism and physical appearance of a medusa (jellyfish). The robotic jellyfish called Robojelly mimics the morphology and kinematics of the Aurelia aurita species. Robojelly actuates using bio-inspired shape memory alloy composite actuators. A systematic fabrication technique was developed to replicate the essential structural features of A. aurita. Robojelly's body was fabricated from RTV silicone having a total mass of 242 g and bell diameter of 164 mm. Robojelly was able to generate enough thrust in static water conditions to propel itself and achieve a proficiency of 0.19 s(-1) while the A. aurita achieves a proficiency of around 0.25 s(-1). A thrust analysis based on empirical measurements for a natural jellyfish was used to compare the performance of the different robotic configurations. The configuration with best performance was a Robojelly with segmented bell and a passive flap structure. Robojelly was found to consume an average power on the order of 17 W with the actuators not having fully reached a thermal steady state.     

Conserved structural and functional control of N-methyl-D-aspartate receptor gating by transmembrane domain M3

The molecular events controlling glutamate receptor ion channel gating are complex. The movement of transmembrane domain M3 within N-methyl-d-aspartate (NMDA) receptor subunits has been suggested to be one structural determinant linking agonist binding to channel gating. Here we report that covalent modification of NR1-A652C or the analogous mutation in NR2A, -2B, -2C, or -2D by methanethiosulfonate ethylammonium (MT-SEA) occurs only in the presence of glutamate and glycine, and that modification potentiates recombinant NMDA receptor currents. The modified channels remain open even after removing glutamate and glycine from the external solution. The degree of potentiation depends on the identity of the NR2 subunit (NR2A < NR2B < NR2C,D) inversely correlating with previous measurements of channel open probability. MTSEA-induced modification of channels is associated with increased glutamate potency, increased mean single-channel open time, and slightly decreased channel conductance. Modified channels are insensitive to the competitive antagonists D-2-amino-5-phosphonovaleric acid (APV) and 7-Cl-kynurenic acid, as well as allosteric modulators of gating (extracellular protons and Zn(2+)). However, channels remain fully sensitive to Mg(2+) blockade and partially sensitive to pore block by (+)MK-801, (-)MK-801, ketamine, memantine, amantadine, and dextrorphan. The partial sensitivity to (+)MK-801 may reflect its ability to stimulate agonist unbinding from MT-SEA-modified receptors. In summary, these data suggest that the SYTANLAAF motif within M3 is a conserved and critical determinant of channel gating in all NMDA receptors.     

Characterization and calculation of a cytochrome c-cytochrome b5 complex using NMR data

To identify the binding site for bovine cytochrome b(5) (cyt b(5)) on horse cytochrome c (cyt c), cross-saturation transfer NMR experiments were performed with (2)H- and (15)N-enriched cyt c and unlabeled cyt b(5). In addition, chemical shift changes of the cyt c backbone amide and side chain methyl resonances were monitored as a function of cyt b(5) concentration. The chemical shift changes indicate that the complex is in fast exchange, and are consistent with a 1:1 stoichiometry. A K(a) of (4 +/- 3) x 10(5) M(-)(1) was obtained with a lower limit of 855 s(-)(1) for the dissociation rate of the complex. Mapping of the chemical shift variations and intensity changes upon cross-saturation NMR experiments in the complex reveals a single, contiguous interaction interface on cyt c. Using NMR data as constraints, a protein docking program was used to calculate two low-energy model complex clusters. Independent calculations of the effect of the cyt b(5) heme ring current-induced magnetic dipole on cyt c were used to discriminate between the different models. The interaction surface of horse cyt c in the current experimentally constrained model of the cyt c-cyt b(5) complex is similar but not identical to the interface predicted in yeast cyt c by Brownian dynamics and docking calculations. The occurrence of different amino acids at the protein-protein interface and the dissimilar assumptions employed in the calculations can largely account for the nonidentical interfaces.     

Different effects of subchronic doses of 17-beta estradiol in two ethologically based models of anxiety utilizing female rats

Estrogen may have differing effects on 'anxiety' responses under different conditions. The current study tested the effects of estrogen on anxiety-like behavior when administered for 6-7 days in ovariectomized (OVX) female rats. Two animal paradigms were utilized; the elevated plus maze (EPM), measuring changes in innate fear of exploration of open spaces; and the social interaction test (SIT), measuring the exploration of a novel, same gender partner. In the EPM, estradiol-treated OVX females both entered and spent more time in the open arms than control OVX females, indicating an anxiolytic-like action of estradiol. In contrast, estradiol treated OVX females interacted less with the partner animal in the SIT compared with controls suggesting anxiogenic-like effects. The possible anxiogenic effect of estradiol in the SIT is supported by two findings: (1) the effect is reversed by the anxiolytic drug alprazolam and (2) estrogen did not affect locomotion and therefore, the reduced social interaction is not due to reduced activity. Acute administration of progesterone (5 mg/kg), which has anxiolytic properties, did not reverse estradiol-induced social interaction deficits, suggesting that lack of progesterone did not account for estradiol's anxiogenic effects. These results, while seemingly contradictory when interpreted within a unified concept of anxiety, may well reflect the ethological roles of reproductive hormones and their effects on different types of exploratory anxiety.     

Hydration of enzyme in nonaqueous media is consistent with solvent dependence of its activity

Water plays an important role in enzyme structure and function in aqueous media. That role becomes even more important when one focuses on enzymes in low water media. Here we present results from molecular dynamics simulations of surfactant-solubilized subtilisin BPN' in three organic solvents (octane, tetrahydrofuran, and acetonitrile) and in pure water. Trajectories from simulations are analyzed with a focus on enzyme structure, flexibility, and the details of enzyme hydration. The overall enzyme and backbone structures, as well as individual residue flexibility, do not show significant differences between water and the three organic solvents over a timescale of several nanoseconds currently accessible to large-scale molecular dynamics simulations. The key factor that distinguishes molecular-level details in different media is the partitioning of hydration water between the enzyme and the bulk solvent. The enzyme surface and the active site region are well hydrated in aqueous medium, whereas with increasing polarity of the organic solvent (octane --> tetrahydrofuran --> acetonitrile) the hydration water is stripped from the enzyme surface. Water stripping is accompanied by the penetration of tetrahydrofuran and acetonitrile molecules into crevices on the enzyme surface and especially into the active site. More polar organic solvents (tetrahydrofuran and acetonitrile) replace mobile and weakly bound water molecules in the active site and leave primarily the tightly bound water in that region. In contrast, the lack of water stripping in octane allows efficient hydration of the active site uniformly by mobile and weakly bound water and some structural water similar to that in aqueous solution. These differences in the active site hydration are consistent with the inverse dependence of enzymatic activity on organic solvent polarity and indicate that the behavior of hydration water on the enzyme surface and in the active site is an important determinant of biological function especially in low water media.     

Chaperone activity and prodan binding at the self-associating domain of erythroid spectrin

Spectrin, the major constituent protein of the erythrocyte membrane skeleton, exhibits chaperone activity by preventing the irreversible aggregation of insulin at 25 degrees C and that of alcohol dehydrogenase at 50 degrees C. The dimeric spectrin and the two subunits, alpha-spectrin and beta-spectrin prevent such aggregation appreciably better, 70% in presence of dimeric spectrin at an insulin:spectrin ratio of 1:1, than that in presence of the tetramer of 25%. Our results also show that spectrin binds to denatured enzymes alpha-glucosidase and alkaline phosphatase during refolding and the reactivation yields are increased in the presence of the spectrin derivatives when compared with those refolded in their absence. The unique hydrophobic binding site on spectrin for the fluorescence probe, 6-propionyl-2-(dimethylamino)naphthalene (Prodan) has been established to localize at the self-associating domain with the binding stoichiometry of one Prodan/both dimeric and tetrameric spectrin. The other fluorescence probe, 1-anilinonaphthalene-8-sulfonic acid, does not show such specificity for spectrin, and the binding stoichiometry is between 3 and 5 1-anilinonaphthalene-8-sulfonic acid/dimeric and tetrameric spectrin, respectively. Regions in alpha- and beta-spectrins have been found to have sequence homology with known chaperone proteins. More than 50% similarities in alpha-spectrin near the N terminus with human Hsp90 and in beta-spectrin near the C terminus with human Hsp90 and Escherichia coli DnaJ have been found, indicating a potential chaperone-like sequence to be present near the self-associating domain that is formed by portions of alpha-spectrin near the N terminus and the beta-spectrin near the C terminus. There are other patches of sequences also in both the spectrin polypeptides, at the other termini as well as in the middle of the rod domain having significant homology with well known chaperone proteins.     

Brevetoxin activation of voltage-gated sodium channels regulates Ca dynamics and ERK1/2 phosphorylation in murine neocortical neurons

Voltage-gated sodium channels (VGSC) are involved in the generation of action potentials in neurons. Brevetoxins (PbTx) are potent allosteric enhancers of VGSC function and are associated with the periodic 'red tide' blooms. Using PbTx-2 as a probe, we have characterized the effects of activation of VGSC on Ca(2+) dynamics and extracellular signal-regulated kinases 1/2 (ERK1/2) signaling in neocortical neurons. Neocortical neurons exhibit synchronized spontaneous Ca(2+) oscillations, which are mediated by glutamatergic signaling. PbTx-2 (100 nm) increased the amplitude and reduced the frequency of basal Ca(2+) oscillations. This modulatory effect on Ca(2+) oscillations produced a sustained rise in ERK1/2 activation. At 300 nm, PbTx-2 disrupted oscillatory activity leading to a sustained increase in intracellular Ca(2+) ([Ca(2+)](i)) and induced a biphasic, activation followed by dephosphorylation, regulation of ERK1/2. PbTx-2-induced ERK1/2 activation was Ca(2+) dependent and was mediated by Ca(2+) entry through manifold routes. PbTx-2 treatment also increased cAMP responsive element binding protein (CREB) phosphorylation and increased gene expression of brain-derived neurotrophic factor (BDNF). These findings indicate that brevetoxins, by influencing the activation of key signaling proteins, can alter physiologic events involved in survival in neocortical neurons, as well as forms of synaptic plasticity associated with development and learning.     

Cloning, purification, and characterization of a non-collagenous anti-angiogenic protein domain from human alpha1 type IV collagen expressed in Sf9 cells

alpha1(IV)NC1, a cleavage fragment of the carboxy terminal non-collagenous human alpha1 chain of type IV collagen, is derived from the extracellular matrix specifically by MMP-2. Recently we determined the in vitro and in vivo anti-angiogenic activity of alpha1(IV)NC1 and presently, its role in cancer therapy is under evaluation. To characterize alpha1(IV)NC1 as a potential candidate for drug development and to test its efficacy in animal models, an effective method to produce a purified active form of alpha1(IV)NC1 is needed. In the present study, expression of alpha1(IV)NC1 in Sf9 cells using baculovirus expression system was discussed, this method was found to be effective in the production of a functionally active soluble form of the recombinant protein. The purified protein showed its characteristic activities such as inhibiting cell proliferation, migration, and tube formation in endothelial cells.