title: A corticosteroid-induced gene expressing an "IsK-like" K+ channel activity in Xenopus oocytes.
abstract: Screening a rat colon cDNA library for aldosterone-induced genes resulted in the molecular cloning of a cDNA whose corresponding mRNA is strongly induced in the colon by dexamethasone, aldosterone, and a low NaCl diet. A similar mRNA was detected in kidney papilla but not in brain, heart, or skeletal muscle. Xenopus laevis oocytes injected with cRNA synthesized from this clone, designated CHIF (channel-inducing factor), express a K(+)-specific channel activity. The biophysical, pharmacological, and regulatory characteristics of this channel are very similar to those reported before for IsK (minK). These include: slow (tau > 20 s) activation by membrane depolarization with a threshold potential above -50 mV, blockade by clofilium, inhibition by phorbol ester, and activation by 8-bromoadenosine 3',5'-cyclic monophosphate and high cytoplasmic Ca2+. The primary structure of this clone, however, shows no homology to IsK. Instead, CHIF exhibits > 50% similarity to two other short bitopic membrane proteins, phospholemman and the gamma subunit of Na+K(+)-ATPase. The data are consistent with the possibility that CHIF is a member of a family of transmembrane regulators capable of activating endogenous oocyte transport proteins.
authors.affiliation: Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: B
authors.initials: B
authors.lastname: Attali
authors.forename: H
authors.initials: H
authors.lastname: Latter
authors.forename: N
authors.initials: N
authors.lastname: Rachamim
authors.forename: H
authors.initials: H
authors.lastname: Garty
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000450:Aldosterone / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D003106:Colon / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D015870:Gene Expression / Q000187:drug effects*; D015723:Gene Library; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000096:biosynthesis* / Q000187:drug effects / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated; D021382:Protein Sorting Signals / Q000096:biosynthesis; D018075:RNA, Complementary / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017386:Sequence Homology, Amino Acid; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: C094337:Fxyd4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D021382:Protein Sorting Signals; D018075:RNA, Complementary; C059983:potassium channel protein I(sk); D015124:8-Bromo Cyclic Adenosine Monophosphate; D000001:Calcimycin; D000450:Aldosterone; D003907:Dexamethasone; D013755:Tetradecanoylphorbol Acetate