TY - JOUR
T1 - Activity of BKCa channel is modulated by membrane cholesterol content and association with Na+/K+-ATPase in human melanoma IGR39 cells
AU - Tajima, Nobuyoshi
AU - Itokazu, Yutaka
AU - Korpi, Esa R.
AU - Somerharju, Pentti
AU - Käkelä, Reijo
PY - 2011/2/18
Y1 - 2011/2/18
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=79953155650&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79953155650&partnerID=8YFLogxK
U2 - 10.1074/jbc.M110.149898
DO - 10.1074/jbc.M110.149898
M3 - Article
C2 - 21135099
AN - SCOPUS:79953155650
SN - 0021-9258
VL - 286
SP - 5624
EP - 5638
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 7
ER -