Alterations in a voltage-gated K+ current during the differentiation of ML-1 human myeloblastic leukemia cells.
A voltage-gated K+ current has been identified in ML-1 human myeloid leukemia cells, with the use of the whole-cell patch-clamp technique. ML-1 cells proliferate in tissue culture as immature myeloblasts and can be induced to differentiate to nonproliferative monocyte/macrophages. In the myeloblastic cells, activation of the K+ current occurs upon depolarization of the membrane potential to above -40 mV; inactivation of this current is also voltage dependent and follows a simple exponential time course with a time constant (Ti) of 900 msec at 0 mV. The current is inhibited by 4-aminopyridine (IC50 of 80 microM at 0 mV), but is much less sensitive to tetraethylammonium of Ba2+. In cells exposed to the differentiation-inducer 12-O-tetradecanoylphorbol-13-acetate (TPA), dramatic alterations in the K+ current occur: upon exposure to 10 nM TPA during whole-cell recording, the amplitude of the voltage-activated current initially increases (within 4 min) and later decreases (at approximately 30-50 min). Upon addition of 0.5 nM TPA to cells in tissue culture, the current shows suppressed activation and accelerated inactivation in the early stages of differentiation (10-fold decrease in Ti at approximately 7 hr) and is completely suppressed in the later stages (3 days). Thus, this voltage-gated K+ current is suppressed early in the induction of differentiation and associated loss of proliferation in myeloid ML-1 cells exposed to TPA; this parallels the fact that channels of a similar type are activated upon the stimulation of proliferation in lymphoid cells exposed to mitogens.(ABSTRACT TRUNCATED AT 250 WORDS)
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Department of Physiology and Biophysics, Wright State University, School of Medicine, Dayton, Ohio 45435.
Yang
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T
Markakis
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Guggino
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Craig
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D015761:4-Aminopyridine / Q000494:pharmacology; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D015470:Leukemia, Myeloid, Acute / Q000473:pathology*; D008564:Membrane Potentials / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D015761:4-Aminopyridine; D013755:Tetradecanoylphorbol Acetate