TY - JOUR
T1 - Bromoenol lactone inhibits voltage-gated Ca 2+ and transient receptor potential canonical channels
AU - Chakraborty, Saikat
AU - Berwick, Zachary C.
AU - Bartlett, Paula J.
AU - Kumar, Sanjay
AU - Thomas, Andrew P.
AU - Sturek, Michael
AU - Tune, Johnathan D.
AU - Obukhov, Alexander G.
PY - 2011/11
Y1 - 2011/11
N2 - Circulating hormones stimulate the phospholipase Cβ (PLC)/Ca 2+ influx pathway to regulate numerous cell functions, including vascular tone. It was proposed previously that Ca 2+- independent phospholipase A 2 (iPLA 2)-dependent store-operated Ca 2+ influx channels mediate hormone-induced contractions in isolated arteries, because bromoenol lactone (BEL), a potent irreversible inhibitor of iPLA 2, inhibited such contractions. However, the effects of BEL on other channels implicated in mediating hormone-induced vessel contractions, specifically voltage-gated Ca 2+ (Ca V1.2) and transient receptor potential canonical (TRPC) channels, have not been defined clearly. Using isometric tension measurements, we found that thapsigargin-induced contractions were ~34% of those evoked by phenylephrine or KCl. BEL completely inhibited not only thapsigargin- but also phenylephrine- and KCl-induced ring contractions, suggesting that Ca V1.2 and receptor-operated TRPC channels also may be sensitive to BEL. Therefore, we investigated the effects of BEL on heterologously expressed Ca V1.2 and TRPC channels in human embryonic kidney cells, a model system that allows probing of individual protein function without interference from other signaling elements of native cells. We found that low micromolar concentrations of BEL inhibited Ca V1.2, TRPC5, TRPC6, and heteromeric TRPC1-TRPC5 channels in an iPLA 2-independent manner. BEL also attenuated PLC activity, suggesting that the compound may inhibit TRPC channel activity in part by interfering with an initial PLC-dependent step required for TRPC channel activation. Conversely, BEL did not affect endogenous voltage-gated K +channels in human embryonic kidney cells. Our findings support the hypothesis that iPLA 2-dependent store-operated Ca 2+influx channels and iPLA 2-independent hormone-operated TRPC channels can serve as smooth muscle depolarization triggers to activate Ca V1.2 channels and to regulate vascular tone.
AB - Circulating hormones stimulate the phospholipase Cβ (PLC)/Ca 2+ influx pathway to regulate numerous cell functions, including vascular tone. It was proposed previously that Ca 2+- independent phospholipase A 2 (iPLA 2)-dependent store-operated Ca 2+ influx channels mediate hormone-induced contractions in isolated arteries, because bromoenol lactone (BEL), a potent irreversible inhibitor of iPLA 2, inhibited such contractions. However, the effects of BEL on other channels implicated in mediating hormone-induced vessel contractions, specifically voltage-gated Ca 2+ (Ca V1.2) and transient receptor potential canonical (TRPC) channels, have not been defined clearly. Using isometric tension measurements, we found that thapsigargin-induced contractions were ~34% of those evoked by phenylephrine or KCl. BEL completely inhibited not only thapsigargin- but also phenylephrine- and KCl-induced ring contractions, suggesting that Ca V1.2 and receptor-operated TRPC channels also may be sensitive to BEL. Therefore, we investigated the effects of BEL on heterologously expressed Ca V1.2 and TRPC channels in human embryonic kidney cells, a model system that allows probing of individual protein function without interference from other signaling elements of native cells. We found that low micromolar concentrations of BEL inhibited Ca V1.2, TRPC5, TRPC6, and heteromeric TRPC1-TRPC5 channels in an iPLA 2-independent manner. BEL also attenuated PLC activity, suggesting that the compound may inhibit TRPC channel activity in part by interfering with an initial PLC-dependent step required for TRPC channel activation. Conversely, BEL did not affect endogenous voltage-gated K +channels in human embryonic kidney cells. Our findings support the hypothesis that iPLA 2-dependent store-operated Ca 2+influx channels and iPLA 2-independent hormone-operated TRPC channels can serve as smooth muscle depolarization triggers to activate Ca V1.2 channels and to regulate vascular tone.
UR - http://www.scopus.com/inward/record.url?scp=80054787641&partnerID=8YFLogxK
U2 - 10.1124/jpet.111.183673
DO - 10.1124/jpet.111.183673
M3 - Article
C2 - 21795434
AN - SCOPUS:80054787641
SN - 0022-3565
VL - 339
SP - 329
EP - 340
JO - Journal of Pharmacology and Experimental Therapeutics
JF - Journal of Pharmacology and Experimental Therapeutics
IS - 2
ER -