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  • Title: The protein IsK is a dual activator of K+ and Cl- channels.
    Author: Attali B, Guillemare E, Lesage F, Honoré E, Romey G, Lazdunski M, Barhanin J.
    Journal: Nature; 1993 Oct 28; 365(6449):850-2. PubMed ID: 8413671.
    Abstract:
    The protein IsK (M(r) 14,500) is present in epithelial cells, heart, uterus and lymphocytes and induces slowly activating K+ currents when expressed in Xenopus oocytes. The finding that mutations of its single transmembrane segment altered channel gating or selectivity has suggested that IsK is a channel-forming protein. But IsK does not exhibit the K+ channel hallmarks (a conserved K+ selective pore (H5) flanked by either six or two membrane-spanning regions). Here we report that IsK expression in Xenopus oocytes also induces a Cl- selective current very similar to the Cl- current produced by phospholemman expression and with biophysical, pharmacological and regulation characteristics very different from those of the IsK-induced K+ channel activity. IsK mutagenesis identifies amino- and carboxy-terminal domains as critical for the induction of Cl- and K+ channel activities, respectively. Our data lead to a model in which the IsK protein (now called IsK, Cl) acts as a potent activator of endogenous and otherwise silent K+ or Cl- channels.
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