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Volume-sensitive chloride currents in four epithelial cell lines are not directly correlated to the expression of the

A Rasola1, L J Galietta, D C Gruenert

  • 1Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, Genova, Italy.

The Journal of Biological Chemistry
|January 14, 1994
PubMed

Insights

The multidrug resistance gene MDR-1 product, P-glycoprotein, does not directly control swelling-induced chloride currents in tested epithelial cells. Chloride conductance amplitude is independent of MDR-1 gene expression levels.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Physiology

Background:

  • The MDR-1 gene product, P-glycoprotein, is implicated in multidrug resistance and potentially possesses chloride channel activity.
  • Previous studies suggested a link between MDR-1 expression and volume-sensitive chloride currents.

Purpose of the Study:

  • To investigate the relationship between MDR-1 gene expression and volume-sensitive chloride currents in human epithelial cell lines.
  • To determine if P-glycoprotein directly influences chloride channel activity.

Main Methods:

  • Utilized four human epithelial cell lines: LoVo/H, LoVo/Dx, 9HTEo-, and 9HTEo-/Dx.
  • Assessed MDR-1 gene expression using reverse transcriptase polymerase chain reaction, indirect immunofluorescence, and Western immunoblot assays.
  • Measured swelling-induced chloride currents to evaluate chloride conductance.

Main Results:

  • Higher P-glycoprotein expression was confirmed in drug-resistant cell lines (LoVo/Dx and 9HTEo-/Dx).
  • The magnitude of swelling-induced chloride currents was similar in drug-sensitive and drug-resistant cell lines.
  • Chloride conductance was significantly higher in 9HTEo- and 9HTEo-/Dx cells compared to LoVo/H and LoVo/Dx cells.

Conclusions:

  • The amplitude of volume-sensitive chloride currents is not directly correlated with MDR-1 gene expression.
  • P-glycoprotein's role in regulating these chloride currents may be indirect or absent.
  • Other cellular mechanisms likely govern the observed chloride conductance in these epithelial cells.

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