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Rat Brain Expresses a Heterogeneous Family of Calcium Channels
Terry P. Snutch, John P. Leonard, Mary M. Gilbert, Henry A. Lester and Norman Davidson
Proceedings of the National Academy of Sciences of the United States of America
Vol. 87, No. 9 (May, 1990), pp. 3391-3395
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2354173
Page Count: 5
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We describe the isolation and characterization of several rat brain cDNAs that are homologous to the α1 subunit of heart and skeletal muscle dihydropyridine-sensitive Ca channels. Northern blot analysis of 32 cDNAs shows that they can be grouped into four distinct classes (A, B, C, and D), each corresponding to a distinct hybridization pattern of brain mRNAs. Southern blot and DNA sequencing suggest that each class of cDNA represents a distinct gene or gene family. In the regions sequenced, the rat brain class C and D gene products share ≈ 75% amino acid identity with the rabbit skeletal muscle Ca channel. In addition, the class C polypeptide is almost identical to the rabbit cardiac Ca channel (97% identity). In contrast, the rat brain class A and B cDNAs are more distantly related to dihydropyridine-sensitive Ca channels (47-64% amino acid identity) and to the brain class C and D genes (51-55% amino acid identity). To examine the functional significance of the isolated brain cDNAs, hybrid depletion experiments were performed in Xenopus oocytes. Antisense oligonucleotides against class A and B cDNAs each partially inhibited, and a class C oligonucleotide almost fully inhibited, the expression of Ba current in rat brain mRNA injected oocytes; but none of the oligonucleotides affected the expression of voltage-gated Na or K conductances. The clone characterization and sequencing results demonstrate that a number of distinct, yet related, voltage-gated Ca-channel genes are expressed in the brain. The antisense oligonucleotide experiments specifically show that one or several of the Ca-channel classes are related to the Ca channels observed in rat brain mRNA injected oocytes.
Proceedings of the National Academy of Sciences of the United States of America © 1990 National Academy of Sciences