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This Article Full Text Full Text (PDF) All Versions of this Article: 289/1/F154    most recent 00331.2004v1 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 (3) Citing Articles via Google Scholar Google Scholar Articles by Breusegem, S. Y. Articles by Levi, M. Search for Related Content PubMed PubMed Citation Articles by Breusegem, S. Y. Articles by Levi, M.

Acute and chronic changes in cholesterol modulate Na-P_i cotransport activity in OK cells

¹Department of Medicine, Division of Renal Diseases and Hypertension, and ²Department of Physiology and Biophysics, University of Colorado Health Sciences Center and Denver Veterans Affairs Medical Center, Denver, Colorado; ³Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas; ⁴Department of Internal Medicine, University of Louisville, Louisville, Kentucky; and ⁵Department of Toxicology, University of Zaragoza, Zaragoza, Spain

Submitted 2 September 2004 ; accepted in final form 24 February 2005

We previously showed an inverse correlation between membrane cholesterol content and Na-P_i cotransport activity during the aging process and adaptation to alterations in dietary P_i in the rat (Levi M, Jameson DM, and van der Meer BW. Am J Physiol Renal Fluid Electrolyte Physiol 256: F85–F94, 1989). The purpose of the present study was to determine whether alterations in cholesterol content per se modulate Na-P_i cotransport activity and apical membrane Na-P_i protein expression in opossum kidney (OK) cells. Acute cholesterol depletion achieved with -methyl cyclodextrin (-MCD) resulted in a significant increase in Na-P_i cotransport activity accompanied by a moderate increase in apical membrane Na-P_i protein abundance and no alteration of total cellular Na-P_i protein abundance. Conversely, acute cholesterol enrichment achieved with -MCD/cholesterol resulted in a significant decrease in Na-P_i cotransport activity with a moderate decrease in apical membrane Na-Pi protein abundance and no change of the total cellular Na-P_i protein abundance. In contrast, chronic cholesterol depletion, achieved by growing cells in lipoprotein-deficient serum (LPDS), resulted in parallel and significant increases in Na-P_i cotransport activity and apical membrane and total cellular Na-P_i protein abundance. Cholesterol depletion also resulted in a significant increase in membrane lipid fluidity and alterations in lipid microdomains as determined by laurdan fluorescence spectroscopy and imaging. Chronic cholesterol enrichment, achieved by growing cells in LPDS followed by loading with low-density lipoprotein, resulted in parallel and significant decreases in Na-P_i cotransport activity and apical membrane and total cellular Na-P_i protein abundance. Our results indicate that in OK cells acute and chronic alterations in cholesterol content per se modulate Na-P_i cotransport activity by diverse mechanisms that also include significant interactions of Na-P_i protein with lipid microdomains.

two-photon fluorescence microscopy; filipin; lipid microdomains; laurdan; opossum kidney cells

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