Cytoplasmic and extracellular IsK peptides activate endogenous K+ and Cl- channels in Xenopus oocytes. Evidence for regulatory function.
IsK is a 14.5-kDa type III membrane glycoprotein which induces slowly activating K+ and Cl- currents when expressed in Xenopus oocytes and HEK 293 cells. Recently, mutagenesis experiments identified amino- and carboxyl-terminal domains of IsK as critical for induction of Cl- and K+ currents, respectively. This hypothesis was tested by examining effects of synthetic IsK hydrophilic peptides on untreated Xenopus oocytes. In agreement with IsK membrane topology, we show here that peptides derived from carboxyl and amino termini are sufficient to activate slow K+ and Cl- channels whose biophysical and pharmacological characteristics are similar to those exhibited by the native IsK protein. That data provide further evidence that IsK is a regulatory subunit of pre-existing silent channel complexes rather than a channel per se.
Ben-Efraim
I
I
Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, 76100 Israel.
Shai
Y
Y
Attali
B
B
D000595:Amino Acid Sequence; D000818:Animals; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology; D005110:Extracellular Space; D015640:Ion Channel Gating / Q000187:drug effects; D008562:Membrane Glycoproteins / Q000737:chemistry; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D010446:Peptide Fragments; D011188:Potassium / Q000502:physiology; D015221:Potassium Channels / Q000737:chemistry / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
D018118:Chloride Channels; D002712:Chlorides; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D000644:Quaternary Ammonium Compounds; C059983:potassium channel protein I(sk); C022799:clofilium; D011188:Potassium