Modulation of volume-sensitive Cl - channels and cell volume by actin filaments and microtubules in human cervical cancer HT-3 cells.
Hypotonicity activates volume-sensitive Cl- currents, which are implicated in the regulatory volume decrease (RVD) responses and transport of taurine in human cervical cancer HT-3 cells. In this study, the role of cytoskeleton in the regulation of volume-sensitive Cl- channels and RVD responses in HT-3 cells was studied. Cells were incubated with various compounds, which depolymerized or polymerized cytoskeletal elements, i.e. actin filaments and microtubules. The hypotonicity-induced changes in Cl- conductance and in cell volume were measured by whole-cell voltage clamping and cell size monitoring, respectively. Our results show that in HT-3 cells hypotonicity activated an outward rectified Cl- current that was abrogated by Cl- channel blockers. Cytochalasin B, an actin-depolymerizing compound, induced a substantial increase in Cl- conductance under isotonic condition and potentiated the expression of Cl- currents in hypotonic stress. Phorbol 12-myristate 13-acetate (PMA) significantly inhibited the cytochalasin B-induced activation of Cl- conductance under isotonic condition. On the other hand, treatment with cytochalasin B significantly prolonged the RVD responses. Phalloidin, a stabilizer of actin polymerization, did not change the basal currents under isotonic condition, but completely abolished the increase in whole-cell Cl- conductance elicited by hypotonicity and retarded the cell volume recovery. Colchicine, a microtubule-assembly inhibitor, had no effect on either basal Cl- conductance or volume-sensitive Cl- current and was unable to inhibit the RVD responses. Taxol, a microtubule-stabilizing compound, did not alter the basal Cl- conductance, but inhibited the activation of volume-sensitive Cl- channels as well as the process of RVD in a dose-dependent manner. These data support the notion that functional integrity of actin filaments and microtubules plays critical roles in maintaining the RVD responses and activation of Cl- channels in human cervical cancer HT-3 cells.
Shen
M R
MR
Department of Obstetrics and Gynecology, National Cheng Kung University Medical College, Tainan, Taiwan.
Chou
C Y
CY
Hsu
K F
KF
Hsu
K S
KS
Wu
M L
ML
D000199:Actins / Q000187:drug effects / Q000502:physiology*; D048429:Cell Size / Q000187:drug effects / Q000502:physiology*; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D003078:Colchicine / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D005260:Female; D006801:Humans; D007038:Hypotonic Solutions; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008870:Microtubules / Q000187:drug effects / Q000502:physiology*; D009997:Osmotic Pressure; D017239:Paclitaxel / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010590:Phalloidine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000473:pathology
D000199:Actins; D018118:Chloride Channels; D007038:Hypotonic Solutions; D010590:Phalloidine; D003571:Cytochalasin B; D013755:Tetradecanoylphorbol Acetate; D017239:Paclitaxel; D003078:Colchicine