HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 287/1/G33    most recent 00023.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Loewen, M. E. Articles by Gabriel, S. E. Search for Related Content PubMed PubMed Citation Articles by Loewen, M. E. Articles by Gabriel, S. E.

MUCOSAL BIOLOGY

pCLCA1 lacks inherent chloride channel activity in an epithelial colon carcinoma cell line

¹Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4; ²Department of Physiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E5; and ³Department of Pediatrics, University of North Carolina, Chapel Hill, North Carolina 27599-7020

Submitted 15 January 2004 ; accepted in final form 18 February 2004

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.

cystic fibrosis transmembrane conductance regulator; cyclic adenosine 5'-monophosphate; ionomycin; calcium

This article has been cited by other articles:

				M. K. Bothe, J. Braun, L. Mundhenk, and A. D. Gruber Murine mCLCA6 Is an Integral Apical Membrane Protein of Non-goblet Cell Enterocytes and Co-localizes With the Cystic Fibrosis Transmembrane Conductance Regulator J. Histochem. Cytochem., May 1, 2008; 56(5): 495 - 509. [Abstract] [Full Text] [PDF]

				A. Gibson, A. P. Lewis, K. Affleck, A. J. Aitken, E. Meldrum, and N. Thompson hCLCA1 and mCLCA3 Are Secreted Non-integral Membrane Proteins and Therefore Are Not Ion Channels J. Biol. Chem., July 22, 2005; 280(29): 27205 - 27212. [Abstract] [Full Text] [PDF]

				M. E. Loewen and G. W. Forsyth Structure and Function of CLCA Proteins Physiol Rev, July 1, 2005; 85(3): 1061 - 1092. [Abstract] [Full Text] [PDF]