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1: Proc Natl Acad Sci U S A. 1991 Jan 1;88(1):53-7.Click here to read Links

Sequence and functional expression in Xenopus oocytes of a human insulinoma and islet potassium channel.

Philipson LH, Hice RE, Schaefer K, LaMendola J, Bell GI, Nelson DJ, Steiner DF.

Department of Medicine, University of Chicago, IL 60637.

Regulation of insulin secretion involves the coordinated control of ion channels in the beta-cell membrane. We have isolated and characterized cDNA and genomic clones encoding a voltage-dependent K+ channel isoform expressed in human islets and in a human insulinoma. This K+ channel isoform, designated hPCN1, with a deduced amino acid sequence of 613 residues (Mr = 67,097), is related to the Shaker family of Drosophila K+ channels. hPCN1 is homologous to two other human K+ channel isoforms we have isolated, hPCN2 and hPCN3, with 55% and 65% amino acid sequence identity, respectively. The electrophysiological characteristics of hPCN1 were determined after microinjection of synthetic RNA into Xenopus oocytes. Two-microelectrode voltage-clamp recordings of oocytes injected with hPCN1 RNA revealed a voltage-dependent outward K+ current that inactivated slowly with time. Outward currents were inhibited by 4-aminopyridine with a Ki less than 0.10 mM and were relatively insensitive to tetraethylammonium ion or Ba2+. A delayed rectifier K+ channel such as hPCN1 could restore the resting membrane potential of beta cells after depolarization and thereby contribute to the regulation of insulin secretion.

PMID: 1986382 [PubMed - indexed for MEDLINE]

PMCID: PMC50746

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