We tested the hypothesis that increased Sarcoplasmic reticulum (SR)
Ca content (Ca(SRT)) in phospholamban knockout mice (PLB-KO)
is because of increased SR Ca pump efficiency defined by the steady-state
SR Ca gradient. The time course of thapsigargin-sensitive ATP-dependent
(45)Ca influx into and efflux out of cardiac SR vesicles from PLB-KO
and wild-type (WT) mice was measured at 100 nm free Ca. We found
that PLB decreased the initial SR Ca uptake rate (0.13 versus 0.31
nmol/mg/s) and decreased steady-state (45)Ca content (0.9 versus
4.1 nmol/mg protein). Furthermore, at similar total SR Ca, the
pump-mediated Ca efflux rate was higher in WT (0.065 versus 0.037
nmol/mg/s). The pump-independent leak rate constant (k(leak)) was
also measured at 100 nm free Ca. The results indicate that k(leak)
was < 1\% of pump-mediated backflux and was not different among nonpentameric
mutant PLB (PLB-C41F), WT pentameric PLB (same expression level),
and PLB-KO. Therefore differences in passive SR Ca leak cannot be
the cause of the higher thapsigargin-sensitive Ca efflux from the
WT membranes. We conclude that the decreased total SR Ca in WT
mice is caused by decreased SR Ca influx rate, an increased Ca-pump
backflux, and unaltered leak. Based upon both thermodynamic and kinetic
analysis, we conclude that PLB decreases the energetic efficiency
of the SR Ca pump.
%0 Journal Article
%1 Shan_2001_7195
%A Shannon, T. R.
%A Chu, G.
%A Kranias, E. G.
%A Bers, D. M.
%D 2001
%J J. Biol. Chem.
%K 11087739 AMP-Dependent ATPase, Action Activation, Adenosine Adrenergic Allosteric Animals, Binding, Biological Biological, Caffeine, Calcium Calcium, Calcium-Binding Cardiac, Cardiovascular, Catalytic Cell Cells, Channels, Computer Congestive, Contraction, Cultured, Cyclic Cytosol, Diastole, Dogs, Domain, Electric Enzyme Exchanger, Factors, Failure, Ferrets, Fibers, Gov't, Heart Heart, Humans, Hydrolysis, Inhibitors, Intracellular Ion Isoproterenol, Kinases, Kinetics, Knockout, Membrane Membrane, Membranes, Mice, Microsomes, Models, Muscle Mutagenesis, Myocardial Myocardium, Myocytes, Nickel, Non-U.S. P.H.S., Phosphorylation, Potentials, Protein Proteins, Rabbits, Red, Regulation, Research Reticulum, Ruthenium Sarcoplasmic Signaling, Simulation, Sodium-Calcium Stimulation, Support, Tetracaine, Thapsigargin, Thermodynamics, Time Transport, Triphosphate, U.S. Ventricles, beta-Agonists, {C}a$^{2+}$-Transporting
%N 10
%P 7195--7201
%R 10.1074/jbc.M007085200
%T Phospholamban decreases the energetic efficiency of the sarcoplasmic
reticulum Ca pump.
%U http://dx.doi.org/10.1074/jbc.M007085200
%V 276
%X We tested the hypothesis that increased Sarcoplasmic reticulum (SR)
Ca content (Ca(SRT)) in phospholamban knockout mice (PLB-KO)
is because of increased SR Ca pump efficiency defined by the steady-state
SR Ca gradient. The time course of thapsigargin-sensitive ATP-dependent
(45)Ca influx into and efflux out of cardiac SR vesicles from PLB-KO
and wild-type (WT) mice was measured at 100 nm free Ca. We found
that PLB decreased the initial SR Ca uptake rate (0.13 versus 0.31
nmol/mg/s) and decreased steady-state (45)Ca content (0.9 versus
4.1 nmol/mg protein). Furthermore, at similar total SR Ca, the
pump-mediated Ca efflux rate was higher in WT (0.065 versus 0.037
nmol/mg/s). The pump-independent leak rate constant (k(leak)) was
also measured at 100 nm free Ca. The results indicate that k(leak)
was < 1\% of pump-mediated backflux and was not different among nonpentameric
mutant PLB (PLB-C41F), WT pentameric PLB (same expression level),
and PLB-KO. Therefore differences in passive SR Ca leak cannot be
the cause of the higher thapsigargin-sensitive Ca efflux from the
WT membranes. We conclude that the decreased total SR Ca in WT
mice is caused by decreased SR Ca influx rate, an increased Ca-pump
backflux, and unaltered leak. Based upon both thermodynamic and kinetic
analysis, we conclude that PLB decreases the energetic efficiency
of the SR Ca pump.
@article{Shan_2001_7195,
abstract = {We tested the hypothesis that increased Sarcoplasmic reticulum (SR)
Ca content ([Ca]({SRT})) in phospholamban knockout mice (PLB-KO)
is because of increased SR Ca pump efficiency defined by the steady-state
SR [Ca] gradient. The time course of thapsigargin-sensitive ATP-dependent
(45)Ca influx into and efflux out of cardiac SR vesicles from PLB-KO
and wild-type (WT) mice was measured at 100 nm free [Ca]. We found
that PLB decreased the initial SR Ca uptake rate (0.13 versus 0.31
nmol/mg/s) and decreased steady-state (45)Ca content (0.9 versus
4.1 nmol/mg protein). Furthermore, at similar total SR [Ca], the
pump-mediated Ca efflux rate was higher in WT (0.065 versus 0.037
nmol/mg/s). The pump-independent leak rate constant (k(leak)) was
also measured at 100 nm free [Ca]. The results indicate that k(leak)
was < 1\% of pump-mediated backflux and was not different among nonpentameric
mutant PLB (PLB-C41F), WT pentameric PLB (same expression level),
and PLB-KO. Therefore differences in passive SR Ca leak cannot be
the cause of the higher thapsigargin-sensitive Ca efflux from the
WT membranes. We conclude that the decreased total SR [Ca] in WT
mice is caused by decreased SR Ca influx rate, an increased Ca-pump
backflux, and unaltered leak. Based upon both thermodynamic and kinetic
analysis, we conclude that PLB decreases the energetic efficiency
of the SR Ca pump.},
added-at = {2009-06-03T11:20:58.000+0200},
author = {Shannon, T. R. and Chu, G. and Kranias, E. G. and Bers, D. M.},
biburl = {https://www.bibsonomy.org/bibtex/24ab608e48305d4d1bdd4fcb3bea1db3d/hake},
description = {The whole bibliography file I use.},
doi = {10.1074/jbc.M007085200},
file = {Shan_2001_7195.pdf:Shan_2001_7195.pdf:PDF},
interhash = {7404778986bf0bba5dde5251a1b034ec},
intrahash = {4ab608e48305d4d1bdd4fcb3bea1db3d},
journal = {J. Biol. Chem.},
key = 104,
keywords = {11087739 AMP-Dependent ATPase, Action Activation, Adenosine Adrenergic Allosteric Animals, Binding, Biological Biological, Caffeine, Calcium Calcium, Calcium-Binding Cardiac, Cardiovascular, Catalytic Cell Cells, Channels, Computer Congestive, Contraction, Cultured, Cyclic Cytosol, Diastole, Dogs, Domain, Electric Enzyme Exchanger, Factors, Failure, Ferrets, Fibers, Gov't, Heart Heart, Humans, Hydrolysis, Inhibitors, Intracellular Ion Isoproterenol, Kinases, Kinetics, Knockout, Membrane Membrane, Membranes, Mice, Microsomes, Models, Muscle Mutagenesis, Myocardial Myocardium, Myocytes, Nickel, Non-U.S. P.H.S., Phosphorylation, Potentials, Protein Proteins, Rabbits, Red, Regulation, Research Reticulum, Ruthenium Sarcoplasmic Signaling, Simulation, Sodium-Calcium Stimulation, Support, Tetracaine, Thapsigargin, Thermodynamics, Time Transport, Triphosphate, U.S. Ventricles, beta-Agonists, {C}a$^{2+}$-Transporting},
month = Mar,
number = 10,
pages = {7195--7201},
pii = {M007085200},
pmid = {11087739},
timestamp = {2009-06-03T11:21:29.000+0200},
title = {Phospholamban decreases the energetic efficiency of the sarcoplasmic
reticulum Ca pump.},
url = {http://dx.doi.org/10.1074/jbc.M007085200},
volume = 276,
year = 2001
}