1995 Fiscal Year Final Research Report Summary
STRUCTURE AND FUNCTION ANALYSIS OF ATP-DEPENDENT K+CHANNEL AND SEROTONIN-SENSITIVE K+CHANNEL
| Project/Area Number |
06680797
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neuroscience in general
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| Research Institution | INTERNATIONAL INSTITUTE FOR ADVANCED STUDIES |
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Principal Investigator |
KUBO Tai INTERNATIONAL INSTITUTE FOR ADVANCED STUDIES SENIOR SCIENTIST, 研究部, 研究員 (10178030)
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| Project Period (FY) |
1994 – 1995
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| Keywords | K+ CHANNEL / cDNA / Aplysia |
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| Research Abstract |
We have cloned the Aplysia counterparts of Shaker superfamilies, AKv1.1, AKv2.1, AKv3.1, and AKv4.1, and Ca2+ activated K+ channels (KCa) by homology screening of the cDNA library prepared from the nervous system. As like mammalian K+ channels, two C-terminal variants for AKv2.1 and 6 for KCa were observed. High conservation of amino acid sequences of H5 region, where is proposed to form channel pore and therefore to be critical for ion selectivity, enabled us to design general primers to the potassium-ion-selective channels. Three new families (two of them were closely related in the amino acid sequence) were thus obtained and termed as AKv5.1, AKv5.2 and AKv6.1. When the sequences of the protein core regions are compared to those of the Shaker superfamily, AKv5.1, AKv5.2 and AKv6.1 apparently form a new family.
AKv1.1, AKv2.1 and AKv5.1 were functionally expressed in Xenopus oocytes by injecting the specific cRNAs synthesized in vitro. AKv1.1 exhibits fast activating and fast inactivating transient K+ current (IA) highly dependent on the voltage. AKv2.1 also exerts fast activating K+ current, while it inactivates very slowly. AKv5.1 expressed in oocytes shows very characteristic electrophysiological features. The current starts to activate around -50 mV.It activates very slowly and doesn't inactivate during the depolarizing pulses for one sec. In order to address the question how these channels contribute to membrane excitability of neuron, we took an advantage of the Aplysia system. AKv1.1 and AKv5.1 cDNAs were injected in Aplysia neuron using the pNEX vector as a vehicle. In a spontaneously bursting cell R15, AKv5.1 exerts an unusual control over cell excitability ; it increased the resting potential and completely abolished the bursting. On the other hand AKv1.1 shortens the duration of the action potential and increases the afterpotential of the spike but does not suppress bursting.
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