Osmotic shrinkage of human cervical cancer cells induces an extracellular Cl- -dependent nonselective cation channel, which requires p38 MAPK.
This study is to integrate a functional role of nonselective cation (NSC) channels into a model of volume regulation on osmotic shrinkage for human cervical cancer cells. Application of a hypertonic solution (400 mosm kg(-1)) induced cell shrinkage, which was accompanied by a 7-fold increase of inward currents at -80 mV from -4.1 +/- 0.4 pA pF(-1) to -29 +/- 1.1 pA pF(-1) (n = 36, p < 0.001). There is a good correlation of channel activity and cell volume changes. Replacement of bath Na(+) by K(+), Cs(+), Li(+), or Rb(+) did not affect the stimulated inward current significantly, but replacement by Ca(2+), Ba(2+), or the impermeable cation N-methyl-d-glucamine abolished the inward current; this demonstrates that the shrinkage-induced currents discriminate poorly between monovalent cations but are not carried by divalent cations. Replacement of extracellular Cl(-) by gluconate abolished the shrinkage-induced currents in a concentration-dependent manner without changing the reversal potential. Gadolinium (Gd(3+)) inhibited the stimulated current, whereas bumetanide and amiloride had no inhibitory effect. Cell shrinkage triggered mitogen-activated protein (MAP) kinase cascades leading to the activation of MAP/extracellular signal-regulated kinase 1/2 (ERK1/2) kinase (MEK1/2), and p38 kinase. Interference with p38 MAPK by either the specific inhibitor (SB202190), or a dominant-negative mutant profoundly suppressed the activation of the shrinkage-induced NSC channels. In contrast, the regulatory mechanism of shrinkage-induced NSC channels was independent of the volume-responsive MEK1/2 signaling pathway. More importantly, the cell volume response to hypertonicity was inhibited significantly in p38 dominant-negative mutant or by SB202190. Therefore, p38 MAPK is critically involved in the activation of a shrinkage-induced NSC channel, which plays an important role in the volume regulation of human cervical cancer cells.
Shen
Meng-Ru
MR
Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan 704, Taiwan.
Chou
Cheng-Yang
CY
Hsu
Keng-Fu
KF
Ellory
J Clive
JC
D015153:Blotting, Western; D002712:Chlorides / Q000378:metabolism*; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009995:Osmosis; D013050:Spectrometry, Fluorescence; D002583:Uterine Cervical Neoplasms / Q000378:metabolism / Q000473:pathology*; D048051:p38 Mitogen-Activated Protein Kinases
D002712:Chlorides; D007473:Ion Channels; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases