cDNA cloning and functional characterization of the mouse Ca2+-gated K+ channel, mIK1. Roles in regulatory volume decrease and erythroid differentiation.
We have cloned from murine erythroleukemia (MEL) cells, thymus, and stomach the cDNA encoding the Ca2+-gated K+ (KCa) channel, mIK1, the mouse homolog of hIK1 (Ishii, T. M., Silvia, C., Hirschberg, B., Bond, C. T., Adelman, J. P., and Maylie, J. (1997) Proc. Natl. Acad. Sci.(U. S. A. 94, 11651-11656). mIK1 mRNA was detected at varied levels in many tissue types. mIK1 KCa channel activity expressed in Xenopus oocytes closely resembled the Kca of red cells (Gardos channel) and MEL cells in its single channel conductance, lack of voltage-sensitivity of activation, inward rectification, and Ca2+ concentration dependence. mIK1 also resembled the erythroid channel in its pharmacological properties, mediating whole cell and unitary currents sensitive to low nM concentrations of both clotrimazole (CLT) and its des-imidazolyl metabolite, 2-chlorophenyl-bisphenyl-methanol, and to low nM concentrations of iodocharybdotoxin. Whereas control oocytes subjected to hypotonic swelling remained swollen, mIK1 expression conferred on oocytes a novel, Ca2+-dependent, CLT-sensitive regulatory volume decrease response. Hypotonic swelling of voltage-clamped mIK1-expressing oocytes increased outward currents that were Ca2+-dependent, CLT-sensitive, and reversed near the K+ equilibrium potential. mIK1 mRNA levels in ES cells increased steadily during erythroid differentiation in culture, in contrast to other KCa mRNAs examined. Low nanomolar concentrations of CLT inhibited proliferation and erythroid differentiation of peripheral blood stem cells in liquid culture.
Molecular Medicine and Renal Units, Beth Israel Deaconess Medical Center Boston, Massachusetts 02215, USA.
D H
DH
Vandorpe
B E
BE
Shmukler
L
L
Jiang
B
B
Lim
J
J
Maylie
J P
JP
Adelman
L
L
de Franceschi
M D
MD
Cappellini
C
C
Brugnara
S L
SL
Alper
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D048429:Cell Size; D003001:Cloning, Molecular; D003022:Clotrimazole / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects; D005622:Friend murine leukemia virus; D006031:Glycosylation; D007038:Hypotonic Solutions; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D015640:Ion Channel Gating; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014981:Xenopus
D018076:DNA, Complementary; D007038:Hypotonic Solutions; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496925:Kcnn4 protein, mouse; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; D003022:Clotrimazole; D002118:Calcium