A Randomized Active-Controlled Study Comparing the Efficacy and Safety of Vernakalant to Amiodarone in Recent-Onset Atrial Fibrillation

ObjectivesThis randomized double-blind study compared the efficacy and safety of intravenous vernakalant and amiodarone for the acute conversion of recent-onset atrial fibrillation (AF).BackgroundIntravenous vernakalant has effectively converted recent-onset AF and was well tolerated in placebo-controlled studies.MethodsA total of 254 adult patients with AF (3 to 48 h duration) eligible for cardioversion were enrolled in the study. Patients received either a 10-min infusion of vernakalant (3 mg/kg) followed by a 15-min observation period and a second 10-min infusion (2 mg/kg) if still in AF, plus a sham amiodarone infusion, or a 60-min infusion of amiodarone (5 mg/kg) followed by a maintenance infusion (50 mg) over an additional 60 min, plus a sham vernakalant infusion.ResultsConversion from AF to sinus rhythm within the first 90 min (primary end point) was achieved in 60 of 116 (51.7%) vernakalant patients compared with 6 of 116 (5.2%) amiodarone patients (p < 0.0001). Vernakalant resulted in rapid conversion (median time of 11 min in responders) and was associated with a higher rate of symptom relief compared with amiodarone (53.4% of vernakalant patients reported no AF symptoms at 90 min compared with 32.8% of amiodarone patients; p = 0.0012). Serious adverse events or events leading to discontinuation of study drug were uncommon. There were no cases of torsades de pointes, ventricular fibrillation, or polymorphic or sustained ventricular tachycardia.ConclusionsVernakalant demonstrated efficacy superior to amiodarone for acute conversion of recent-onset AF. Both vernakalant and amiodarone were safe and well tolerated in this study. (A Phase III Superiority Study of Vernakalant vs Amiodarone in Subjects With Recent Onset Atrial Fibrillation [AVRO]; NCT00668759

Tedisamil and dofetilide-induced torsades de pointes, rate and potassium dependence

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73908/1/sj.bjp.0703967.pd

Cingulin Contains Globular and Coiled-Coil Domains and Interacts with Zo-1, Zo-2, Zo-3, and Myosin

We characterized the sequence and protein interactions of cingulin, an Mr 140–160-kD phosphoprotein localized on the cytoplasmic surface of epithelial tight junctions (TJ). The derived amino acid sequence of a full-length Xenopus laevis cingulin cDNA shows globular head (residues 1–439) and tail (1,326–1,368) domains and a central α-helical rod domain (440–1,325). Sequence analysis, electron microscopy, and pull-down assays indicate that the cingulin rod is responsible for the formation of coiled-coil parallel dimers, which can further aggregate through intermolecular interactions. Pull-down assays from epithelial, insect cell, and reticulocyte lysates show that an NH2-terminal fragment of cingulin (1–378) interacts in vitro with ZO-1 (Kd ∼5 nM), ZO-2, ZO-3, myosin, and AF-6, but not with symplekin, and a COOH-terminal fragment (377–1,368) interacts with myosin and ZO-3. ZO-1 and ZO-2 immunoprecipitates contain cingulin, suggesting in vivo interactions. Full-length cingulin, but not NH2-terminal and COOH-terminal fragments, colocalizes with endogenous cingulin in transfected MDCK cells, indicating that sequences within both head and rod domains are required for TJ localization. We propose that cingulin is a functionally important component of TJ, linking the submembrane plaque domain of TJ to the actomyosin cytoskeleton

A PDZ-containing Scaffold Related to the Dystrophin Complex at the Basolateral Membrane of Epithelial Cells

Membrane scaffolding complexes are key features of many cell types, serving as specialized links between the extracellular matrix and the actin cytoskeleton. An important scaffold in skeletal muscle is the dystrophin-associated protein complex. One of the proteins bound directly to dystrophin is syntrophin, a modular protein comprised entirely of interaction motifs, including PDZ (protein domain named for PSD-95, discs large, ZO-1) and pleckstrin homology (PH) domains. In skeletal muscle, the syntrophin PDZ domain recruits sodium channels and signaling molecules, such as neuronal nitric oxide synthase, to the dystrophin complex. In epithelia, we identified a variation of the dystrophin complex, in which syntrophin, and the dystrophin homologues, utrophin and dystrobrevin, are restricted to the basolateral membrane. We used exogenously expressed green fluorescent protein (GFP)-tagged fusion proteins to determine which domains of syntrophin are responsible for its polarized localization. GFP-tagged full-length syntrophin targeted to the basolateral membrane, but individual domains remained in the cytoplasm. In contrast, the second PH domain tandemly linked to a highly conserved, COOH-terminal region was sufficient for basolateral membrane targeting and association with utrophin. The results suggest an interaction between syntrophin and utrophin that leaves the PDZ domain of syntrophin available to recruit additional proteins to the epithelial basolateral membrane. The assembly of multiprotein signaling complexes at sites of membrane specialization may be a widespread function of dystrophin-related protein complexes

Mitochondrial p32 Is a Critical Mediator of ARF-Induced Apoptosis

The shared exon 2 of the p14ARF-p16INK4a locus is frequently mutated in human cancers. However, in contrast to the exon 1β-encoded N-terminal half of ARF, the function of the exon 2-encoded C-terminal half of ARF has been elusive. Here, we report that the mitochondrial protein p32/C1QBP binds the ARF C terminus. We show that p32 is required for ARF to localize to mitochondria and induce apoptosis, and that ARF mutations specifically disrupting p32 binding can impair both of these functions. Wild-type ARF, but not a p32-binding-deficient ARF mutant, localizes to mitochondria, reduces mitochondrial membrane potential, and sensitizes cells to p53-induced apoptosis. These findings provide a potential explanation for the frequent human cancer mutations targeting the ARF C terminus