Constitutive PKA activity is essential for maintaining the excitability and contractility in guinea pig urinary bladder smooth muscle

Role of the BK channel

Wenkuan Xin, Ning Li, Qiuping Cheng, Vitor S. Fernandes, Georgi Petkov

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The elevation of protein kinase A (PKA) activity activates the largeconductance voltage- and Ca2+-activated K+ (BK) channels in urinary bladder smooth muscle (UBSM) cells and consequently attenuates spontaneous phasic contractions of UBSM. However, the role of constitutive PKA activity in UBSM function has not been studied. Here, we tested the hypothesis that constitutive PKA activity is essential for controlling the excitability and contractility of UBSM. We used patch clamp electrophysiology, line-scanning confocal and ratiometric fluorescence microscopy on freshly isolated guinea pig UBSM cells, and isometric tension recordings on freshly isolated UBSM strips. Pharmacological inhibition of the constitutive PKA activity with H-89 or PKI 14–22 significantly reduced the frequency and amplitude of spontaneous transient BK channel currents (TBKCs) in UBSM cells. Confocal and ratiometric fluorescence microscopy studies revealed that inhibition of constitutive PKA activity with H-89 reduced the frequency and amplitude of the localized Ca2+ sparks but increased global Ca2+ levels and the magnitude of Ca2+ oscillations in UBSM cells. H-89 abolished the spontaneous transient membrane hyperpolarizations and depolarized the membrane potential in UBSM cells. Inhibition of PKA with H-89 or KT-5720 also increased the amplitude and muscle force of UBSM spontaneous phasic contractions. This study reveals the novel concept that constitutive PKA activity is essential for controlling localized Ca2+ signals generated by intracellular Ca2+ stores and cytosolic Ca2+ levels. Furthermore, constitutive PKA activity is critical for mediating the spontaneous TBKCs in UBSM cells, where it plays a key role in regulating spontaneous phasic contractions in UBSM.

Original languageEnglish (US)
Pages (from-to)C1142-C1150
JournalAmerican Journal of Physiology - Cell Physiology
Volume307
Issue number12
DOIs
StatePublished - Dec 15 2014

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Large-Conductance Calcium-Activated Potassium Channels
Cyclic AMP-Dependent Protein Kinases
Smooth Muscle
Guinea Pigs
Urinary Bladder
Smooth Muscle Myocytes
Fluorescence Microscopy
Calcium-Activated Potassium Channels
Electrophysiology
Membrane Potentials

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cell Biology

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Constitutive PKA activity is essential for maintaining the excitability and contractility in guinea pig urinary bladder smooth muscle : Role of the BK channel. / Xin, Wenkuan; Li, Ning; Cheng, Qiuping; Fernandes, Vitor S.; Petkov, Georgi.

In: American Journal of Physiology - Cell Physiology, Vol. 307, No. 12, 15.12.2014, p. C1142-C1150.

Research output: Contribution to journalArticle

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AB - The elevation of protein kinase A (PKA) activity activates the largeconductance voltage- and Ca2+-activated K+ (BK) channels in urinary bladder smooth muscle (UBSM) cells and consequently attenuates spontaneous phasic contractions of UBSM. However, the role of constitutive PKA activity in UBSM function has not been studied. Here, we tested the hypothesis that constitutive PKA activity is essential for controlling the excitability and contractility of UBSM. We used patch clamp electrophysiology, line-scanning confocal and ratiometric fluorescence microscopy on freshly isolated guinea pig UBSM cells, and isometric tension recordings on freshly isolated UBSM strips. Pharmacological inhibition of the constitutive PKA activity with H-89 or PKI 14–22 significantly reduced the frequency and amplitude of spontaneous transient BK channel currents (TBKCs) in UBSM cells. Confocal and ratiometric fluorescence microscopy studies revealed that inhibition of constitutive PKA activity with H-89 reduced the frequency and amplitude of the localized Ca2+ sparks but increased global Ca2+ levels and the magnitude of Ca2+ oscillations in UBSM cells. H-89 abolished the spontaneous transient membrane hyperpolarizations and depolarized the membrane potential in UBSM cells. Inhibition of PKA with H-89 or KT-5720 also increased the amplitude and muscle force of UBSM spontaneous phasic contractions. This study reveals the novel concept that constitutive PKA activity is essential for controlling localized Ca2+ signals generated by intracellular Ca2+ stores and cytosolic Ca2+ levels. Furthermore, constitutive PKA activity is critical for mediating the spontaneous TBKCs in UBSM cells, where it plays a key role in regulating spontaneous phasic contractions in UBSM.

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