Staff – Department of Biology - University of Copenhagen

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Cholesterol modulates the volume-regulated anion current in Ehrlich-Lettre ascites cells via effects on Rho and F-actin.

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Thomas Kjaer Klausen, Charlotte Hougaard, Else K Hoffmann, Stine F Pedersen

The mechanisms controlling the volume-regulated anion current (VRAC) are incompletely elucidated. Here, we investigate the modulation of VRAC by cellular cholesterol and the potential involvement of F-actin, Rho, Rho kinase, and phosphatidylinositol-(4,5)-bisphosphate [PtdIns(4,5)P(2)] in this process. In Ehrlich-Lettre ascites (ELA) cells, a current with biophysical and pharmacological properties characteristic of VRAC was activated by hypotonic swelling. A 44% increase in cellular cholesterol content had no detectable effects on F-actin organization or VRAC activity. A 47% reduction in cellular cholesterol content increased cortical and stress fiber-associated F-actin content in swollen cells. Cholesterol depletion increased VRAC activation rate and maximal current after a modest (15%), but not after a severe (36%) reduction in extracellular osmolarity. The cholesterol depletion-induced increase in maximal VRAC current was prevented by F-actin disruption using latrunculin B (LB), while the current activation rate was unaffected by LB, but dependent on Rho kinase. Rho activity was decreased by approximately 20% in modestly, and approximately 50% in severely swollen cells. In modestly swollen cells, this reduction was prevented by cholesterol depletion, which also increased isotonic Rho activity. Thrombin, which stimulates Rho and causes actin polymerization, potentiated VRAC in modestly swollen cells. VRAC activity was unaffected by inclusion of a water-soluble PtdIns(4,5)P(2) analogue or a PtdIns(4,5)P(2)-blocking antibody in the pipette, or neomycin treatment to sequester PtdIns(4,5)P(2). It is suggested that in ELA cells, F-actin and Rho-Rho kinase modulate VRAC magnitude and activation rate, respectively, and that cholesterol depletion potentiates VRAC at least in part by preventing the hypotonicity-induced decrease in Rho activity and eliciting actin polymerization.
Original languageEnglish
JournalAmerican Journal of Physiology: Cell Physiology
Issue number4
Pages (from-to)C757-71
StatePublished - 2006

Bibliographical note

Keywords: Actins; Amides; Animals; Anions; Bicyclo Compounds, Heterocyclic; Carcinoma, Ehrlich Tumor; Cell Line, Tumor; Cell Size; Chloride Channels; Cholesterol; Electric Conductivity; Enzyme Inhibitors; Hypotonic Solutions; Intracellular Signaling Peptides and Proteins; Ion Channels; Phosphatidylinositol Phosphates; Polymers; Protein-Serine-Threonine Kinases; Pyridines; Thiazoles; Thiazolidines; rho GTP-Binding Proteins; rho-Associated Kinases

ID: 6768621