Novobiocin as an Allosteric Modulator of Ste2p

G protein-coupled receptors (GPCRs) are the target of 30-50% of all prescribed drugs for human medicine and are therefore the subject of intense study by the scientific community. It has been recognized recently that compounds called allosteric modulators can regulate GPCR activity by binding a GPCR at sites not occupied by the normal receptor-activating molecule. Such allosteric compounds are desirable drug candidates as they may produce fewer toxic side-effects than standard drugs that target GPCRs. The purpose of this study was to determine the interaction of different allosteric modulators with Ste2p, a model GPCR expressed in the yeast Saccharomyces cerevisiae. An allosteric peptide, [Bio-DOPA]11-mer, was chemically cross-linked into Ste2p in the presence and absence of another allosteric modulator, the antibiotic novobiocin. The receptor was isolated, collected, and then visualized by protein immunoblot. One of the blots detected the presence of the receptor, and the second blot detected the presence of the biotinylated ligand-receptor complex containing the cross-linked [Bio-DOPA]11-mer. Analysis of the blots revealed that the receptor was present in all of the samples and that there was significantly less [Bio-DOPA]11-mer cross-linked to the receptor in the presence of novobiocin. This experiment demonstrated that both novobiocin and [Bio-DOPA]11-mer competed for a similar site of the receptor. Thus, these two compounds that are very different in their chemical structure occupy a similar allosteric site to regulate GPCR activity. Further experimental analysis may provide insights into the mechanisms utilized by these compounds to influence GPCR function. These results may prove useful in the optimization of allosteric modulators as therapeutic agents for GPCR-based pathologies

Structures controlling volcanic activity within Masaya caldera, Nicaragua

Geophysical and geological observations collected in 2007-2012 shed light on the mechanisms controlling the style and location of eruptions within the Las Sierras-Masaya Caldera complex, Nicaragua. These results confirm a hypothesised ~3.5 km diameter structure with features compatible with the presence of a ring fracture (50-65°, with inward-dipping bounding walls). A central block is bound by this fracture and defines an incipient nested caldera related to the emptying of the magma chamber following the last Plinian eruption (1.8 ka). The prolongation of the Cofradías fault from the Managua graben represents the most significant structure on the floor of Masaya caldera. Current activity, including a convecting lava lake, largely depends on the interplay between the extensional stress regime associated with the Managua graben and deformation along the inner caldera bounding fault. This high spatial resolution survey uses a novel combination of geophysical methodologies to identify previously overlooked foci for future volcanic activity at Masaya

Human genetics and neuropathology suggest a link between miR-218 and amyotrophic lateral sclerosis pathophysiology

Motor neuron-specific microRNA-218 (miR-218) has recently received attention because of its roles in mouse development. However, miR-218 relevance to human motor neuron disease was not yet explored. Here, we demonstrate by neuropathology that miR-218 is abundant in healthy human motor neurons. However, in amyotrophic lateral sclerosis (ALS) motor neurons, miR-218 is down-regulated and its mRNA targets are reciprocally up-regulated (derepressed). We further identify the potassium channel Kv10.1 as a new miR-218 direct target that controls neuronal activity. In addition, we screened thousands of ALS genomes and identified six rare variants in the human miR-218-2 sequence. miR-218 gene variants fail to regulate neuron activity, suggesting the importance of this small endogenous RNA for neuronal robustness. The underlying mechanisms involve inhibition of miR-218 biogenesis and reduced processing by DICER. Therefore, miR-218 activity in motor neurons may be susceptible to failure in human ALS, suggesting that miR-218 may be a potential therapeutic target in motor neuron disease