Cloning and Functional Expression of a Voltage-gated Calcium Channel α1 Subunit from Jellyfish*
- From the Whitney Laboratory and the §Departments of Physiology and Neuroscience, University of Florida, St. Augustine, Florida 32086
Abstract
Voltage-gated Ca2+channels in vertebrates comprise at least seven molecular subtypes, each of which produces a current with distinct kinetics and pharmacology. Although several invertebrate Ca2+ channel α1 subunits have also been cloned, their functional characteristics remain unclear, as heterologous expression of a full-length invertebrate channel has not previously been reported. We have cloned a cDNA encoding the α1 subunit of a voltage-gated Ca2+ channel from the scyphozoan jellyfishCyanea capillata, one of the earliest existing organisms to possess neural and muscle tissue. The deduced amino acid sequence of this subunit, named CyCaα1, is more similar to vertebrateL-type channels (α1S, α1C, and α1D) than to non-L-type channels (α1A, α1B, and α1E) or low voltage-activated channels (α1G). Expression of CyCaα1 in Xenopus oocytes produces a high voltage-activated Ca2+ current that, unlike vertebrateL-type currents, is only weakly sensitive to 1,4-dihydropyridine or phenylalkylamine Ca2+ channel blockers and is not potentiated by the agonist S(−)-BayK 8644. In addition, the channel is less permeable to Ba2+than to Ca2+ and is more permeable to Sr2+. CyCaα1 thus represents an ancestral L-type α1 subunit with significant functional differences from mammalian L-type channels.
Footnotes
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↵* This work was supported in part by National Science Foundation Grant IBN-9410565 (to P. A. V. A.), University of Florida Division of Sponsored Research Grant 94022315 (to R. M. G.), and National Research Service Award MH 10625 (to M. C. J.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) U93075.
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↵‡ Supported by a Research Experience for Undergraduates Grant IBN-9222803 from the National Science Foundation.
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↵¶ To whom correspondence should be addressed: the Whitney Laboratory, University of Florida, 9505 Ocean Shore Blvd., St. Augustine, FL 32086. Tel.: 904-461-4028; Fax: 904-461-4008; E-mail:paa{at}whitney.ufl.edu.
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↵2 R. Greenberg, unpublished observations.
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↵3 M. C. Jeziorski, unpublished observations.
- Abbreviations:
- DHP
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dihydropyridine
- HVA
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high voltage-activated
- LVA
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low voltage-activated
- PCR
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polymerase chain reaction
- RT
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reverse transcription
- kb
-
kilobase pairs
- BAPTA
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1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid.
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- Received April 16, 1998.
- Revision received June 5, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
