Ca(2+)-activated Cl- channels in Ehrlich ascites tumor cells are distinct from mCLCA1, 2 and 3.
Using the whole-cell patch-clamp technique, we have studied the electrophysiological and pharmacological properties of the Ca(2+)-activated Cl- current present in Ehrlich cells. The currents activated slowly upon depolarization, deactivated upon hyperpolarization, and showed strong outward rectification. An increase in [Ca2+]i activated the current with an EC50 of 165.2 nM. Extracellular application of niflumic acid (100 microM) rapidly blocked the current in a voltage-dependent manner whereas sulfhydryl-modifying agents such as dithiothreitol (DTT, 1-2 mM) and N-ethylmaleimide (NEM, 100 microM) had no effect on Ca(2+)-activated currents in Ehrlich cells. Members of the recently discovered CLCA gene family are the only molecular candidates for Ca(2+)-activated Cl- channels cloned so far. Using RT-PCR we demonstrated that the appearance of a Ca(2+)-activated Cl- current in Ehrlich cells is not associated with the expression of the murine members of the CLCA family (mCLCA1-mCLCA3). Correspondingly, the kinetic and pharmacological properties of the Ca(2+)-activated current in Ehrlich cells differ from those of CLCA-associated currents, which are time independent and DTT sensitive. Thus, phenotypic differences in combination with RT-PCR data point to the existence of different molecular species for Ca(2+)-activated Cl- channels.
Papassotiriou
J
J
Laboratorium voor Fysiologie, KU Leuven, Campus Gasthuisberg, 3000 Leuven, Belgium.
Eggermont
J
J
Droogmans
G
G
Nilius
B
B
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism* / Q000473:pathology; D018118:Chloride Channels / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D051379:Mice; D008815:Mice, Inbred Strains; D009088:Mucoproteins / Q000378:metabolism*; D009544:Niflumic Acid / Q000494:pharmacology; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014407:Tumor Cells, Cultured
C492109:CLCA1 protein, human; D018118:Chloride Channels; C492299:Clca2 protein, mouse; C116464:Clca3a1 protein, mouse; D009088:Mucoproteins; D013439:Sulfhydryl Reagents; D009544:Niflumic Acid; D005033:Ethylmaleimide; D002118:Calcium; D004229:Dithiothreitol