Phospholemman-phosphorylation mediates the β-adrenergic effects on Na/K pump function in cardiac myocytes

Sanda Despa, Julie B C Bossuyt, Fei Han, Kenneth S Ginsburg, Li Guo Jia, Howard Kutchai, Amy L. Tucker, Donald M Bers

Research output: Contribution to journalArticle

137 Citations (Scopus)

Abstract

Cardiac sympathetic stimulation activates β-adrenergic (β-AR) receptors and protein kinase A (PKA) phosphorylation of proteins involved in myocyte Ca regulation. The Na/K-ATPase (NKA) is essential in regulating intracellular [Na] ([Na]i), which in turn affects [Ca]i via Na/Ca exchange. However, how PKA modifies NKA function is unknown. Phospholemman (PLM), a member of the FXYD family of proteins that interact with NKA in various tissues, is a major PKA substrate in heart. Here we tested the hypothesis that PLM phosphorylation is responsible for the PKA effects on cardiac NKA function using wild-type (WT) and PLM knockout (PLM-KO) mice. We measured NKA-mediated [Na]i decline and current (IPump) to assess β-AR effects on NKA function in isolated myocytes. In WT myocytes, 1 μmol/L isoproterenol (ISO) increased PLM phosphorylation and stimulated NKA activity mainly by increasing its affinity for internal Na (Km decreased from 18.8± 1.4 to 13.6 ± 1.5 mmol/L), with no significant effect on the maximum pump rate. This led to a significant decrease in resting [Na]i (from 12.5 ± 1.8 to 10.5 ± 1.4 mmol/L). In PLM-KO mice under control conditions Km (14.2 ± 1.5 mmol/L) was lower than in WT, but comparable to that for WT in the presence of ISO. Furthermore, ISO had no significant effect on NKA function in PLM-KO mice. ATPase activity in sarcolemmal vesicles also showed a lower K m(Na) in PLM-KO versus WT (12.9 ± 0.9 versus 16.2 ± 1.5). Thus, PLM inhibits NKA activity by decreasing its [Na]i affinity, and this inhibitory effect is relieved by PKA activation. We conclude that PLM modulates the NKA function in a manner similar to the way phospholamban affects the related SR Ca-ATPase (inhibition of transport substrate affinity, that is relieved by phosphorylation).

Original languageEnglish (US)
Pages (from-to)252-259
Number of pages8
JournalCirculation Research
Volume97
Issue number3
DOIs
StatePublished - Aug 5 2005
Externally publishedYes

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Cardiac Myocytes
Adrenergic Agents
Phosphorylation
Cyclic AMP-Dependent Protein Kinases
Isoproterenol
Muscle Cells
Adenosine Triphosphatases
sodium-translocating ATPase
phospholemman
Knockout Mice
Adrenergic Receptors
Proteins

Keywords

  • Ion channels
  • Na pump
  • Phospholemman
  • Signal transduction

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Phospholemman-phosphorylation mediates the β-adrenergic effects on Na/K pump function in cardiac myocytes. / Despa, Sanda; Bossuyt, Julie B C; Han, Fei; Ginsburg, Kenneth S; Jia, Li Guo; Kutchai, Howard; Tucker, Amy L.; Bers, Donald M.

In: Circulation Research, Vol. 97, No. 3, 05.08.2005, p. 252-259.

Research output: Contribution to journalArticle

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AU - Despa, Sanda

AU - Bossuyt, Julie B C

AU - Han, Fei

AU - Ginsburg, Kenneth S

AU - Jia, Li Guo

AU - Kutchai, Howard

AU - Tucker, Amy L.

AU - Bers, Donald M

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N2 - Cardiac sympathetic stimulation activates β-adrenergic (β-AR) receptors and protein kinase A (PKA) phosphorylation of proteins involved in myocyte Ca regulation. The Na/K-ATPase (NKA) is essential in regulating intracellular [Na] ([Na]i), which in turn affects [Ca]i via Na/Ca exchange. However, how PKA modifies NKA function is unknown. Phospholemman (PLM), a member of the FXYD family of proteins that interact with NKA in various tissues, is a major PKA substrate in heart. Here we tested the hypothesis that PLM phosphorylation is responsible for the PKA effects on cardiac NKA function using wild-type (WT) and PLM knockout (PLM-KO) mice. We measured NKA-mediated [Na]i decline and current (IPump) to assess β-AR effects on NKA function in isolated myocytes. In WT myocytes, 1 μmol/L isoproterenol (ISO) increased PLM phosphorylation and stimulated NKA activity mainly by increasing its affinity for internal Na (Km decreased from 18.8± 1.4 to 13.6 ± 1.5 mmol/L), with no significant effect on the maximum pump rate. This led to a significant decrease in resting [Na]i (from 12.5 ± 1.8 to 10.5 ± 1.4 mmol/L). In PLM-KO mice under control conditions Km (14.2 ± 1.5 mmol/L) was lower than in WT, but comparable to that for WT in the presence of ISO. Furthermore, ISO had no significant effect on NKA function in PLM-KO mice. ATPase activity in sarcolemmal vesicles also showed a lower K m(Na) in PLM-KO versus WT (12.9 ± 0.9 versus 16.2 ± 1.5). Thus, PLM inhibits NKA activity by decreasing its [Na]i affinity, and this inhibitory effect is relieved by PKA activation. We conclude that PLM modulates the NKA function in a manner similar to the way phospholamban affects the related SR Ca-ATPase (inhibition of transport substrate affinity, that is relieved by phosphorylation).

AB - Cardiac sympathetic stimulation activates β-adrenergic (β-AR) receptors and protein kinase A (PKA) phosphorylation of proteins involved in myocyte Ca regulation. The Na/K-ATPase (NKA) is essential in regulating intracellular [Na] ([Na]i), which in turn affects [Ca]i via Na/Ca exchange. However, how PKA modifies NKA function is unknown. Phospholemman (PLM), a member of the FXYD family of proteins that interact with NKA in various tissues, is a major PKA substrate in heart. Here we tested the hypothesis that PLM phosphorylation is responsible for the PKA effects on cardiac NKA function using wild-type (WT) and PLM knockout (PLM-KO) mice. We measured NKA-mediated [Na]i decline and current (IPump) to assess β-AR effects on NKA function in isolated myocytes. In WT myocytes, 1 μmol/L isoproterenol (ISO) increased PLM phosphorylation and stimulated NKA activity mainly by increasing its affinity for internal Na (Km decreased from 18.8± 1.4 to 13.6 ± 1.5 mmol/L), with no significant effect on the maximum pump rate. This led to a significant decrease in resting [Na]i (from 12.5 ± 1.8 to 10.5 ± 1.4 mmol/L). In PLM-KO mice under control conditions Km (14.2 ± 1.5 mmol/L) was lower than in WT, but comparable to that for WT in the presence of ISO. Furthermore, ISO had no significant effect on NKA function in PLM-KO mice. ATPase activity in sarcolemmal vesicles also showed a lower K m(Na) in PLM-KO versus WT (12.9 ± 0.9 versus 16.2 ± 1.5). Thus, PLM inhibits NKA activity by decreasing its [Na]i affinity, and this inhibitory effect is relieved by PKA activation. We conclude that PLM modulates the NKA function in a manner similar to the way phospholamban affects the related SR Ca-ATPase (inhibition of transport substrate affinity, that is relieved by phosphorylation).

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