Dataset Information

Coexpression of rat P2X2 and P2X6 subunits in Xenopus oocytes.

ABSTRACT: Transcripts for P2X(2) and P2X(6) subunits are present in rat CNS and frequently colocalize in the same brainstem nuclei. When rat P2X(2) (rP2X(2)) and rat P2X(6) (rP2X(6)) receptors were expressed individually in Xenopus oocytes and studied under voltage-clamp conditions, only homomeric rP2X(2) receptors were fully functional and gave rise to large inward currents (2-3 microA) to extracellular ATP. Coexpression of rP2X(2) and rP2X(6) subunits in Xenopus oocytes resulted in a heteromeric rP2X(2/6) receptor, which showed a significantly different phenotype from the wild-type rP2X(2) receptor. Differences included reduction in agonist potencies and, in some cases (e.g., Ap(4)A), significant loss of agonist activity. ATP-evoked inward currents were biphasic at the heteromeric rP2X(2/6) receptor, particularly when Zn(2+) ions were present or extracellular pH was lowered. The pH range was narrower for H(+) enhancement of ATP responses at the heteromeric rP2X(2/6) receptor. Also, H(+) ions inhibited ATP responses at low pH levels (

SUBMITTER: King BF

PROVIDER: S-EPMC6772291 | biostudies-literature | 2000 Jul

REPOSITORIES: biostudies-literature

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Coexpression of rat P2X2 and P2X6 subunits in Xenopus oocytes.

King B F BF Townsend-Nicholson A A Wildman S S SS Thomas T T Spyer K M KM Burnstock G G

The Journal of neuroscience : the official journal of the Society for Neuroscience 20000701 13

Transcripts for P2X(2) and P2X(6) subunits are present in rat CNS and frequently colocalize in the same brainstem nuclei. When rat P2X(2) (rP2X(2)) and rat P2X(6) (rP2X(6)) receptors were expressed individually in Xenopus oocytes and studied under voltage-clamp conditions, only homomeric rP2X(2) receptors were fully functional and gave rise to large inward currents (2-3 microA) to extracellular ATP. Coexpression of rP2X(2) and rP2X(6) subunits in Xenopus oocytes resulted in a heteromeric rP2X(2/ ...[more]

PMID: 10864944

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Project description:The mammalian nervous system expresses proton-gated ion channels known as acid-sensing ion channels (ASICs). Depending on their location and specialization some neurons express more than one type of ASIC where they may form homo- or heteromeric channels. Macroscopic characteristics of the ASIC currents have been described, but little is known at the single channel level. Here, we have examined the properties of unitary currents of homomeric rat ASIC1alpha, ASIC2a, and ASIC3 expressed in Xenopus oocytes with the patch clamp technique. We describe and characterize properties unique to each of these channels that can be used to distinguish the various types of ASIC channels expressed in mammalian neurons. The amplitudes of the unitary currents in symmetrical Na(+) are similar for the three types of channels (23-18 pS) and are not voltage dependent. However, ASIC1alpha exhibits three subconductance states, ASIC2a exhibits only one, and ASIC3 none. The kinetics of the three types of channels are different: ASIC1alpha and ASIC2a shift between modes of activity, each mode has different open probability and kinetics. In contrast, the kinetics of ASIC3 are uniform throughout the burst of activity. ASIC1alpha, ASIC2a, and ASIC3 are activated by external protons with apparent pH(50) of 5.9, 5.0, and 5.4, respectively. Desensitization in the continual presence of protons is fast and complete in ASIC1alpha and ASIC3 (2.0 and 4.5 s(-1), respectively) but slow and only partial in ASIC2a (0.045 s(-1)). The response to external Ca(2+) also differs: micro M concentrations of extracellular Ca(2+) are necessary for proton gating of ASIC3 (EC(50) = 0.28 micro M), whereas ASIC1alpha and ASIC2a do not require Ca(2+). In addition, Ca(2+) inhibits ASIC1alpha (K(D) = 9.2 +/- 2 mM) by several mechanisms: decrease in the amplitude of unitary currents, shortening of the burst of activity, and decrease in the number of activated channels. Contrary to previous reports, our results indicate that the Ca(2+) permeability of ASIC1alpha is very small.

Dataset Information

Coexpression of rat P2X2 and P2X6 subunits in Xenopus oocytes.

Publications

Coexpression of rat P2X2 and P2X6 subunits in Xenopus oocytes.

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