Activity of BKCa channel is modulated by membrane cholesterol content and association with Na+/K+-ATPase in human melanoma IGR39 cells

Nobuyoshi Tajima, Yutaka Itokazu, Esa R. Korpi, Pentti Somerharju, Reijo Käkelä

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

Interaction of large conductance Ca2+- and voltage-activated K+ (BKCa) channels with Na+/K +-ATPase, caveolin-1, and cholesterol was studied in human melanoma IGR39 cells. Functional BKCa channels were enriched in caveolin-rich and detergent-resistant membranes, i.e. rafts, and blocking of the channels by a specific BKCa blocker paxilline reduced proliferation of the cells. Disruption of rafts by selective depletion of cholesterol released BK Ca channels from these domains with a consequent increase in their activity. Consistently, cholesterol enrichment of the cells increased the proportion of BKCa channels in rafts and decreased their activity. Immunocytochemical analysis showed that BKCa channels co-localize with Na+/K+-ATPase in a cholesterol-dependent manner, thus suggesting their co-presence in rafts. Supporting this, ouabain, a specific blocker of Na+/K+-ATPase, inhibited BKCa whole-cell current markedly in control cells but not in cholesterol-depleted ones. This inhibition required the presence of external Na+. Collectively, these data indicate that the presence of Na+/K +-ATPase in rafts is essential for efficient functioning of BK Ca channels, presumably because the pump maintains a low intracellular Na+ proximal to the BKCa channel. In conclusion, cholesterol could play an important role in cellular ion homeostasis and thus modulate many cellular functions and cell proliferation.

Original languageEnglish (US)
Pages (from-to)5624-5638
Number of pages15
JournalJournal of Biological Chemistry
Volume286
Issue number7
DOIs
StatePublished - Feb 18 2011

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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