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Voltage-gated Potassium Channels (voltage-gated + potassium_channel)
Selected AbstractsHeteromeric K+ channels in plantsTHE PLANT JOURNAL, Issue 6 2008Anne Lebaudy Summary Voltage-gated potassium channels of plants are multimeric proteins built of four ,-subunits. In the model plant Arabidopsis thaliana, nine genes coding for K+ channel ,-subunits have been identified. When co-expressed in heterologous expression systems, most of them display the ability to form heteromeric K+ channels. Till now it was not clear whether plants use this potential of heteromerization to increase the functional diversity of potassium channels. Here, we designed an experimental approach employing different transgenic plant lines that allowed us to prove the existence of heteromeric K+ channels in plants. The chosen strategy might also be useful for investigating the activity and function of other multimeric channel proteins like, for instance, cyclic-nucleotide gated channels, tandem-pore K+ channels and glutamate receptor channels. [source] Injury-induced neurogenesis in Bax-deficient mice: evidence for regulation by voltage-gated potassium channelsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2007Jian Shi Abstract Adult neural stem and progenitor cells may help remodel the brain in response to injury. The pro-apoptotic molecule Bax has recently been identified as a key player in adult neural stem cell survival. In Bax-deficient mice that have undergone traumatic brain injury, we find increased numbers of neural progenitor cells in the dentate gyrus and improved remodeling of the hippocampus. Exogenous potassium chloride mimics spreading depression (SD)-like events in vitro, and Bax-deficient neural stem cells proliferate in response to these events more robustly than wild-type neural stem cells. Selective potassium channel blockers interrupt SD-mediated stimulation of stem cells. In addition, the potassium channel Kv4.1 is expressed within neural stem and progenitor cells in the dentate gyrus and is increased in Bax-deficiency. These data suggest that the neuroprotection observed after injury in Bax-deficiency may be due to increased neurogenesis via activation of the Kv4 family of potassium channels. [source] A possible molecular mechanism of hanatoxin binding-modified gating in voltage-gated K+ -channelsJOURNAL OF MOLECULAR RECOGNITION, Issue 6 2003Kuo-Long Lou Abstract While S4 is known as the voltage sensor in voltage-gated potassium channels, the carboxyl terminus of S3 (S3C) is of particular interest concerning the site for gating modifier toxins like hanatoxin. The thus derived helical secondary structural arrangement for S3C, as well as its surrounding environment, has since been intensively and vigorously debated. Our previous structural analysis based on molecular simulation has provided sufficient information to describe reasonable docking conformation and further experimental designs (Lou et al., 2002. J. Mol. Recognit. 15: 175,179). However, if one only relies on such information, more advanced structure,functional interpretations for the roles S3C may play in the modification of gating behavior upon toxin binding will remain unknown. In order to have better understanding of the molecular details regarding this issue, we have performed the docking simulation with the S3C sequence from the hanatoxin-insensitive K+ -channel, shaker, and analyzed the conformational changes resulting from such docking. Compared with other functional data from previous studies with respect to the proximity of the S3,S4 linker region, we suggested a significant movement of drk1 S3C, but not shaker S3C, in the direction presumably towards S4, which was comprehended as a possible factor interfering with S4 translocation during drk1 gating in the presence of toxin. In combination with the discussions for structural roles of the length of the S3,S4 linker, a possible molecular mechanism to illustrate the hanatoxin binding-modified gating is proposed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Multiple functions of the paranodal junction of myelinated nerve fibers,JOURNAL OF NEUROSCIENCE RESEARCH, Issue 15 2009Jack Rosenbluth Abstract Myelin sheaths include an extraordinary structure, the "paranodal axoglial junction" (PNJ), which attaches the sheath to the axon at each end of each myelin segment. Its size is enormous and its structure unique. Here we review past and current studies showing that this junction can serve multiple functions in maintaining reliable saltatory conduction. The present evidence points to three functions in particular. 1) It seals the myelin sheath to the axon to prevent major shunting of nodal action currents beneath the myelin sheath while still leaving a narrow channel interconnecting the internodal periaxonal space with the perinodal space. This pathway represents a potential route through which juxtaparanodal and internodal channels can influence nodal activity and through which nutrients, such as glucose, and other metabolites can diffuse to and from the internodal periaxonal space. 2) It serves as a mechanism for maintaining discrete, differentiated axolemmal domains at and around the node of Ranvier by acting as a barrier to the lateral movement of ion channel complexes within the axolemma, thus concentrating voltage-gated sodium channels at the node and segregating fast voltage-gated potassium channels to the juxtaparanode under the myelin sheath. 3) It attaches the myelin sheath to the axon on either side of the node and can thus maintain nodal dimensions in the face of mechanical stresses associated with stretch or other local factors that might cause disjunction. It is therefore the likely means for maintaining constancy of nodal surface area and electrical parameters essential for consistency in conduction. © 2009 Wiley-Liss, Inc. [source] Morvan's syndrome: Clinical, laboratory, and in vitro electrophysiological studiesMUSCLE AND NERVE, Issue 2 2004Wolfgang N. Löscher MD Abstract Morvan's syndrome is a rare disorder characterized by neuromyotonia, hyperhidrosis, and central nervous system dysfunction. We report a patient with features of this syndrome, but who initially presented with breathing difficulties. Concentric needle electromyography showed an abundance of myokymic and neuromyotonic discharges. Exercise tests and repetitive nerve stimulation showed a decrement,increment response of compound muscle action potentials. Antibodies against voltage-gated potassium channels were not detected on repeated testing, but the presence of oligoclonal bands in the cerebrospinal fluid (CSF) suggested an autoimmune etiology. At follow-up over 3 years, no cancer was found. Electrophysiological in vitro studies of effects of patient serum and CSF on rat nerves provided no evidence of altered voltage-gated sodium or potassium conductances. We conclude that putative humoral factors do not block ion channels acutely but may cause channel dysfunction with chronic exposure. Muscle Nerve 30: 157,163, 2004 [source] | ||||||||||