Bromoenol lactone inhibits voltage-gated Ca 2+ and transient receptor potential canonical channels

Saikat Chakraborty, Zachary C. Berwick, Paula Bartlett, Sanjay Kumar, Andrew Thomas, Michael Sturek, Johnathan D. Tune, Alexander G. Obukhov

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

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 V 1.2) 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 V 1.2 and receptor-operated TRPC channels also may be sensitive to BEL. Therefore, we investigated the effects of BEL on heterologously expressed Ca V 1.2 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 V 1.2, 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 V 1.2 channels and to regulate vascular tone.

Original languageEnglish (US)
Pages (from-to)329-340
Number of pages12
JournalJournal of Pharmacology and Experimental Therapeutics
Volume339
Issue number2
DOIs
StatePublished - Nov 1 2011

Fingerprint

Transient Receptor Potential Channels
Phospholipases A
Type C Phospholipases
Hormones
Thapsigargin
Phenylephrine
Blood Vessels
Kidney
Voltage-Gated Potassium Channels
6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one
Smooth Muscle
Arteries

All Science Journal Classification (ASJC) codes

  • Molecular Medicine
  • Pharmacology

Cite this

Chakraborty, Saikat ; Berwick, Zachary C. ; Bartlett, Paula ; Kumar, Sanjay ; Thomas, Andrew ; Sturek, Michael ; Tune, Johnathan D. ; Obukhov, Alexander G. / Bromoenol lactone inhibits voltage-gated Ca 2+ and transient receptor potential canonical channels In: Journal of Pharmacology and Experimental Therapeutics. 2011 ; Vol. 339, No. 2. pp. 329-340.
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abstract = "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 V 1.2) 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 V 1.2 and receptor-operated TRPC channels also may be sensitive to BEL. Therefore, we investigated the effects of BEL on heterologously expressed Ca V 1.2 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 V 1.2, 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 V 1.2 channels and to regulate vascular tone.",
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Bromoenol lactone inhibits voltage-gated Ca 2+ and transient receptor potential canonical channels . / Chakraborty, Saikat; Berwick, Zachary C.; Bartlett, Paula; Kumar, Sanjay; Thomas, Andrew; Sturek, Michael; Tune, Johnathan D.; Obukhov, Alexander G.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 339, No. 2, 01.11.2011, p. 329-340.

Research output: Contribution to journalArticle

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AU - Chakraborty, Saikat

AU - Berwick, Zachary C.

AU - Bartlett, Paula

AU - Kumar, Sanjay

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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 V 1.2) 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 V 1.2 and receptor-operated TRPC channels also may be sensitive to BEL. Therefore, we investigated the effects of BEL on heterologously expressed Ca V 1.2 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 V 1.2, 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 V 1.2 channels and to regulate vascular tone.

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