Voltage-gated potassium (K(v)) channels work in concert with other ion channels to determine the frequency and duration of action potentials in excitable cells. Little is known about K(v)3 channels from invertebrates, but those that have been characterized generally display slow kinetics. Here, we report the cloning and characterization of jShaw1, the first K(v)3 isolated from a cnidarian, the jellyfish Polyorchis penicillatus, in comparison with mouse K(v)3.
View Article and Find Full Text PDFVoltage sensitivity of voltage-gated potassium channels (VKCs) is a primary factor in shaping action potentials in excitable cells. Variation in the amino acid sequence of the channel proteins is responsible for differences in the voltage range over which the channel opens. Thus, understanding how changes in voltage sensitivity are effected by changes in channel protein sequence illuminates the functional evolution of excitability.
View Article and Find Full Text PDFAnaesthesia is often used in neurophysiological, surgical, and neuroanatomical protocols. Several anaesthetics, including magnesium chloride, volatiles (halothane, etc.), and barbiturates, have been used in gastropod neurobiology.
View Article and Find Full Text PDFBackground: Voltage-gated ion channels are membrane proteins containing a selective pore that allows permeable ions to transit the membrane in response to a change in the transmembrane voltage. The typical selectivity filter in potassium channels is formed by a tetrameric arrangement of the carbonyl groups of the conserved amino-acid sequence Gly-Tyr-Gly. This canonical pore is opened or closed by conformational changes that originate in the voltage sensor (S4), a transmembrane helix with a series of positively charged amino acids.
View Article and Find Full Text PDFWe applied compartmental computer modeling to test a model of spike shape change in the jellyfish, Polyorchis penicillatus, to determine whether adaptive spike shortening can be attributed to the inactivation properties of a potassium channel. We modeled the jellyfish outer nerve-ring as a continuous linear segment, using ion channel and membrane properties derived in earlier studies. The model supported action potentials that shortened as they propagated away from the site of initiation and this was found to be largely independent of potassium channel inactivation.
View Article and Find Full Text PDFDivergence of the Shaker superfamily of voltage-gated (Kv) ion channels early in metazoan evolution created numerous electrical phenotypes that were presumably selected to produce a wide range of excitability characteristics in neurons, myocytes, and other cells. A comparative approach that emphasizes this early radiation provides a comprehensive sampling of sequence space that is necessary to develop generally applicable models of the structure-function relationship in the Kv potassium channel family. We have cloned and characterized two Shaw-type potassium channels from a flatworm (Notoplana atomata) that is arguably a representative of early diverging bilaterians.
View Article and Find Full Text PDFVoltage-gated ion channels of the Kv4 subfamily produce A-type currents whose properties are tuned by accessory subunits termed KChIPs, which are a family of Ca2+ sensor proteins. By modifying expression levels and the intrinsic biophysical properties of Kv4 channels, KChIPs modulate the excitability properties of neurons and myocytes. We studied how a Kv4 channel from a tunicate, the first branching clade of the chordates, is modulated by endogenous KChIP subunits.
View Article and Find Full Text PDFCertain neurons of vertebrates are specialized for high-frequency firing. Interestingly, high-frequency firing is also seen in central neurons in basal bilateral metazoans. Recently, the role of potassium currents with rightward-shifted activation curves in producing high-frequency firing has come under scrutiny.
View Article and Find Full Text PDF1. Feeding in the medusa of Proboscidactyla flavicirrata is accompanied by local, small amplitude impulses recorded from the bases of perradial tentacles. 2.
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