Potassium (K ϩ ) channels are essential to neuronal signaling and survival. Here we show that these proteins are targets of reactive oxygen species in mammalian brain and that their oxidation contributes to neuropathy. Thus, the KCNB1 (Kv2.1) channel, which is abundantly expressed in cortex and hippocampus, formed oligomers upon exposure to oxidizing agents. These oligomers were ϳ10-fold more abundant in the brain of old than young mice. Oxidant-induced oligomerization of wild-type KCNB1 enhanced apoptosis in neuronal cells subject to oxidative insults. Consequently, a KCNB1 variant resistant to oxidation, obtained by mutating a conserved cysteine to alanine, (C73A), was neuroprotective. The fact that oxidation of KCNB1 is toxic, argues that this mechanism may contribute to neuropathy in conditions characterized by high levels of oxidative stress, such as Alzheimer's disease (AD). Accordingly, oxidation of KCNB1 channels was exacerbated in the brain of a triple transgenic mouse model of AD (3xTg-AD). The C73A variant protected neuronal cells from apoptosis induced by incubation with ␤-amyloid peptide (A␤ 1-42 ). In an invertebrate model (Caenorhabditis elegans) that mimics aspects of AD, a C73A-KCNB1 homolog (C113S-KVS-1) protected specific neurons from apoptotic death induced by ectopic expression of human A␤ 1-42 . Together, these data underscore a novel mechanism of toxicity in neurodegenerative disease. IntroductionPotassium (K ϩ ) channels are a diverse and ubiquitous family of ion-channels that operate in nonexcitable and excitable cells. K ϩ channels are essential for the function of the nervous system where they modulate the shape and frequency of action potentials and consequently, neurotransmitter release. As such, conditions that result in the impairment of K ϩ channels have the potential to cause neuronal dysfunction by affecting the excitability of the cell, which is intrinsically dependent on these proteins. For example, mutations in KCNQ2, KCNQ3, KCNMA1, KCNA1 and KCNC3 genes which lead to the synthesis of mutants with defective properties have been identified in patients affected by epilepsy, ataxia and episodic ataxia type 1 (for review, see Kullmann, 2002). In addition to genetic predisposition, acquired impairment of K ϩ channel's function can lead to neurological diseases, such as, acquired neuromyotonia, limbic encephalitis, and Morvan's syndrome (for review, see Vernino, 2007).Oxygen metabolism leads to the synthesis of reactive and thus potentially toxic molecules known as reactive oxygen species (ROS). The increase in unbuffered ROS levels in a cell, a phenomenon commonly referred to as oxidative stress, is thought to cause significant cellular damage and to contribute to cellular aging (Harman, 1956). Moreover, oxidative stress is elevated in neuropathies such as Alzheimer's disease (AD) (for review, see Lin and Beal, 2006). Oxidative damage occurs early in AD, before the onset of significant plaque formation (Nunomura et al., 2001;Praticò et al., 2001;Reddy et al., 2004), and consequent...

Background: Oxidation of KCNB1 channels leads to oligomerization and apoptosis. Results: KCNB1 oligomers aggregate in and disrupt glycolipid raft organization, promoting the activation of the Src/JNK pro-apoptotic pathway. Conclusion: KCNB1 aggregates initiate an apoptotic cascade mediated by c-Src/JNK kinases. Significance: Oxidized KCNB1 channels increase in aging mammalian brain. As such, this mechanism contributes to neuronal aging and neurodegeneration.

Background:The physiological role of Rab11a in mouse embryogenesis has not been fully studied. Results: Using a Rab11a null mouse allele, the transport of multiple membrane-associated and soluble cargos was analyzed in mouse blastocysts and MEFs. Conclusion: Rab11a ablation impairs mouse blastocyst development and the secretion of soluble matrix metalloproteinases. Significance: In vivo functions of Rab11a in mouse fetal development and soluble MMP secretion were uncovered.

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J. Neurochem. (2011) 117, 654–664. Abstract Reactive oxygen species (ROS) are produced early during apoptosis of cerebellar granule neurons induced by low potassium (K5) and staurosporine (Sts). In addition, K5 and Sts activate NADPH oxidases (NOX). Recently, we described that K5 and Sts induce apoptotic volume decrease (AVD) at a time when ROS generation and NOX activity occur. In the present study, we evaluated the relationship between ROS generation and ionic fluxes during AVD. Here, we showed that K5‐ and Sts‐induced AVD was inhibited by antioxidants and that direct ROS production induced AVD. Moreover, NOX inhibitors eliminated AVD induced by both K5 and Sts. Sts, but not K5, failed to induce AVD in cerebellar granule neurons from NOX2 knockout mice. These findings suggest that K5‐ and Sts‐induced AVD is largely mediated by ROS produced by NOX. On the other hand, we also found that the blockage of ionic fluxes involved in AVD inhibited both ROS generation and NOX activity. These findings suggest that ROS generation and NOX activity are involved in ionic fluxes activation, which in turn could maintain ROS generation by activating NOX, leading to a self‐amplifying cycle.