Synergistic activation of guinea‐pig cardiac cystic fibrosis transmembrane conductance regulator by the tyrosine kinase inhibitor genistein and cAMP

• Lesya M. Shuba

• Terence F. McDonald

抄録

<jats:list list-type="explicit-label"> The regulation of cardiac Cl − current ( I C1 ) by tyrosine and serine/threonine phosphorylation was examined in guinea‐pig and rat ventricular myocytes. The protein tyrosine kinase (PTK) inhibitor genistein (GST) and phosphotyrosine phosphatase (PTP) inhibitor sodium orthovanadate (VO 4 ) were used to modify tyrosine phosphorylation, whereas forskolin (FSK), cAMP, and other agents were used to modify cytoplasmic cAMP concentration and protein kinase A (PKA) phosphorylation. Low concentrations (0.1 μ m ) of FSK did not activate the PKA‐regulated cystic fibrosis transmembrane regulator (CFTR) I Cl in guinea‐pig ventricular myocytes, but strongly potentiated activation of an I Cl by 20–100 μ m GST. The potentiation did not occur when GST was replaced by PTK‐inactive daidzein, and it was strongly inhibited by 1 m m VO 4 . Potentiation by 0.1 μ m FSK was linked to a small stimulation of the adenylate cyclase–cAMP–PKA pathway. The potentiation was not mimicked by inactive 1,9‐dideoxyforskolin, and was inhibited by muscarinic stimulation (ACh) and by a PKA inhibitor. Internal application of a cAMP solution that alone was too weak to activate CFTR I Cl strongly potentiated the activation of I Cl by 50 μ m GST and occluded potentiation by 0.1 μ m FSK. The foregoing suggests that potentiated I Cl flows through cAMP‐dependent CFTR channels. In agreement with this interpretation, GST did not increase I Cl when CFTR was maximally activated by a high concentration (5 μ m ) of FSK and okadaic acid, and neither GST nor GST plus FSK activated an I Cl in CFTR‐deficient rat myocytes. The lack of effect in rat myocytes was not due to the absence of functional, channel‐relevant PKA and PTK–PTP systems, because (as in guinea‐pig myocytes) L‐type Ca 2+ current ( I Ca,L ) was stimulated by FSK and inhibited in a VO 4 ‐reversible manner by GST. The synergistic activation of CFTR by low concentrations of FSK and GST cannot be explained by either a GST‐induced elevation of cAMP concentration or inhibition of serine/threonine phosphatase. Rather, it appears to be due to tyrosine dephosphorylation that facilitates PKA‐mediated phosphorylation of the channels.

収録刊行物

• The Journal of Physiology

  The Journal of Physiology 505 (1), 23-40, 1997-11

  Wiley

キーワード

• Physiology

詳細情報

• CRID: 1363107368293328256
• NII論文ID: 30022489218
• DOI: 10.1111/j.1469-7793.1997.023bc.x
• ISSN: 14697793
• ISSN: 00223751
• ISSN: http://id.crossref.org/issn/00223751
• Web Site: https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1469-7793.1997.023bc.x
• Web Site: https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7793.1997.023bc.x
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