pCLCA1 lacks inherent chloride channel activity in an epithelial colon carcinoma cell line
| Autor: | Wolfgang Walz, Matthew E. Loewen, Sherif E. Gabriel, George W. Forsyth, Lane K. Bekar |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
medicine.medical_specialty
Time Factors Swine Physiology chemistry.chemical_element Calcium chemistry.chemical_compound Chlorides Chloride Channels Physiology (medical) Internal medicine Cyclic AMP medicine Animals Humans Cellular Senescence Chloride channel activity Hepatology biology Carcinoma Electric Conductivity Gastroenterology Cell Polarity Cell Differentiation Adenosine Cystic fibrosis transmembrane conductance regulator Epithelium Cell biology Endocrinology medicine.anatomical_structure chemistry Cell culture Colonic Neoplasms Ionomycin biology.protein Caco-2 Cells Intracellular medicine.drug |
| Zdroj: | American Journal of Physiology-Gastrointestinal and Liver Physiology. 287:G33-G41 |
| ISSN: | 1522-1547 0193-1857 |
| DOI: | 10.1152/ajpgi.00023.2004 |
| Popis: | The effects of CLCA protein expression on the regulation of Cl− conductance by intracellular Ca2+ and cAMP have been studied previously in nonepithelial cell lines chosen for low backgrounds of endogenous Cl− conductance. However, CLCA proteins have been cloned from, and normally function in, differentiated epithelial cells. In this study, we examine the effects of differentiation of the Caco-2 epithelial colon carcinoma cell line on modulation of Cl− conductance by pCLCA1 protein expression. Cl− transport was measured as 36Cl− efflux, as transepithelial short-circuit currents, and as whole cell patch-clamp current-voltage relations. The rate of 36Cl− efflux and amplitude of currents in patch-clamp studies after the addition of the Ca2+ ionophore A-23187 were increased significantly by pCLCA1 expression in freshly passaged Caco-2 cells. However, neither endogenous nor pCLCA1-dependent Ca2+-sensitive Cl− conductance could be detected in 14-day-postpassage cells. In contrast to Ca2+-sensitive Cl− conductance, endogenous cAMP-dependent Cl− conductance does not disappear on Caco-2 differentiation. cAMP-dependent Cl− conductance was modulated by pCLCA1 expression in Caco-2 cells, and this modulation was observed in freshly passaged and in mature 14-day-postpassage Caco-2 cultures. pCLCA1 mRNA expression, antigenic pCLCA1 protein epitope expression, and pCLCA1 function as a modulator of cAMP-dependent Cl− conductance were retained through differentiation in Caco-2 cells, whereas Ca2+-dependent Cl− conductance disappeared. We conclude that pCLCA1 expression may increase the sensitivity of preexisting endogenous Cl− channels to Ca2+ and cAMP agonists but apparently lacks inherent Cl− channel activity under growth conditions where endogenous channels are not expressed. |
| Databáze: | OpenAIRE |
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