N-type inactivation of the potassium channel KcsA by the Shaker B "ball" Peptide: Mapping the inactivating peptide-binding epitope

10 pags, 6 figsThe effects of the inactivating peptide from the eukaryotic Shaker B K + channel (the ShB peptide) on the prokaryotic KcsA channel have been studied using patch clamp methods. The data show that the peptide induces rapid, N-type inactivation in KcsA through a process that includes functional uncoupling of channel gating. We have also employed saturation transfer difference (STD) NMR methods to map the molecular interactions between the inactivating peptide and its channel target. The results indicate that binding of the ShB peptide to KcsA involves the ortho and meta protons of Tyr 8, which exhibit the strongest STD effects; the C4H in the imidazole ring of His16; the methyl protons of Val4, Leu 7, and Leu10 and the side chain amine protons of one, if not both, the Lys18 and Lys19 residues. When a noninactivating ShB-L7E mutant is used in the studies, binding to KcsA is still observed but involves different amino acids. Thus, the strongest STD effects are now seen on the methyl protons of Val4 and Leu10, whereas His16 seems similarly affected as before. Conversely, STD effects on Tyr8 are strongly diminished, and those on Lys18 and/or Lys19 are abolished. Additionally, Fourier transform infrared spectroscopy of KcsA in presence of 13C-labeled peptide derivatives suggests that the ShB peptide, but not the ShB-L7E mutant, adopts a β-hairpin structure when bound to the KcsA channel. Indeed, docking such a β-hairpin structure into an open pore model for K+ channels to simulate the inactivating peptide/channel complex predicts interactions well in agreement with the experimental observations. © 2008 by The American Society for Biochemistry and Molecular Biology, Inc.This work was supported by Spanish Ministerio de Educación y Ciencia Grants CTQ2005-00360/BQU (to J. L. N.) and BFU2005-00749 (to J. M. G.-R.);FIPSE Experiment 36557/06 (to J. L. N.) and Grant BANCAJA-UMH IP/UR/01;and Consellería de Empresa, Universidad y Ciencia de la Generalitat Valenciana Grant GV07/017 (to J. A. E.)

Clinical Implications of Epigenetic Dysregulation in Perinatal Hypoxic-Ischemic Brain Damage

Placental and fetal hypoxia caused by perinatal hypoxic-ischemic events are major causes of stillbirth, neonatal morbidity, and long-term neurological sequelae among surviving neonates. Brain hypoxia and associated pathological processes such as excitotoxicity, apoptosis, necrosis, and inflammation, are associated with lasting disruptions in epigenetic control of gene expression contributing to neurological dysfunction. Recent studies have pointed to DNA (de)methylation, histone modifications, and non-coding RNAs as crucial components of hypoxic-ischemic encephalopathy (HIE). The understanding of epigenetic dysregulation in HIE is essential in the development of new clinical interventions for perinatal HIE. Here, we summarize our current understanding of epigenetic mechanisms underlying the molecular pathology of HI brain damage and its clinical implications in terms of new diagnostic, prognostic, and therapeutic tools.Fil: Bustelo, Martí. Universidad de Buenos Aires; Argentina. Maastricht University Medical Center; Países Bajos. Universidad Católica de Cuyo - Sede San Juan; ArgentinaFil: Barkhuizen, Melinda. Maastricht University Medical Center; Países BajosFil: van den Hove, Daniel L. A.. Universiteit Maastricht.; Países BajosFil: Steinbusch, Harry Wilhelm. M.. Universiteit Maastricht.; Países BajosFil: Bruno, Martin. Universidad Católica de Cuyo - Sede San Juan; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Loidl, Cesar Fabian. Universidad Catolica de Cuyo - Sede San Luis; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Gavilanes, Antonio W. Danilo. Maastricht University Medical Cente; Países Bajo

A new glassfrog (Centrolenidae) from the Chocó-Andean Río Manduriacu Reserve, Ecuador, endangered by mining

We describe a new glassfrog from Río Manduriacu Reserve, Imbabura Province, on the Pacific slopes of the Ecuadorian Andes. The new species can be distinguished from most other glassfrogs by having numerous yellow spots on the dorsum and lacking membranes among fingers. Both morphological and molecular data support the placement of the species in the genus Nymphargus. We present a new mitochondrial phylogeny of Nymphargus and discuss the speciation patterns of this genus; most importantly, recent speciation events seem to result from the effect of the linearity of the Andes. Finally, although the new species occurs within a private reserve, it is seriously endangered by mining activities; thus, following IUCN criteria, we consider the new species as Critically Endangered