title: Tight coupling of Na+/K+-ATPase with glycolysis demonstrated in permeabilized rat cardiomyocytes.
abstract: The effective integrated organization of processes in cardiac cells is achieved, in part, by the functional compartmentation of energy transfer processes. Earlier, using permeabilized cardiomyocytes, we demonstrated the existence of tight coupling between some of cardiomyocyte ATPases and glycolysis in rat. In this work, we studied contribution of two membrane ATPases and whether they are coupled to glycolysis--sarcoplasmic reticulum Ca2+ ATPase (SERCA) and plasmalemma Na+/K+-ATPase (NKA). While SERCA activity was minor in this preparation in the absence of calcium, major role of NKA was revealed accounting to ∼30% of the total ATPase activity which demonstrates that permeabilized cell preparation can be used to study this pump. To elucidate the contribution of NKA in the pool of ATPases, a series of kinetic measurements was performed in cells where NKA had been inhibited by 2 mM ouabain. In these cells, we recorded: ADP- and ATP-kinetics of respiration, competition for ADP between mitochondria and pyruvate kinase (PK), ADP-kinetics of endogenous PK, and ATP-kinetics of total ATPases. The experimental data was analyzed using a series of mathematical models with varying compartmentation levels. The results show that NKA is tightly coupled to glycolysis with undetectable flux of ATP between mitochondria and NKA. Such tight coupling of NKA to PK is in line with its increased importance in the pathological states of the heart when the substrate preference shifts to glucose.
authors.affiliation: Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia.
authors.forename: Mervi
authors.initials: M
authors.lastname: Sepp
authors.affiliation: Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia.
authors.forename: Niina
authors.initials: N
authors.lastname: Sokolova
authors.affiliation: Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Jugai
authors.affiliation: Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia.
authors.forename: Merle
authors.initials: M
authors.lastname: Mandel
authors.affiliation: Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia.
authors.forename: Pearu
authors.initials: P
authors.lastname: Peterson
authors.affiliation: Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia.
authors.forename: Marko
authors.initials: M
authors.lastname: Vendelin
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000201:enzymology; D002463:Cell Membrane Permeability; D005260:Female; D006019:Glycolysis; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism; D008955:Models, Cardiovascular; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009840:Oligomycins / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D011770:Pyruvate Kinase / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000502:physiology; D012966:Sodium Cyanide / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: C506948:Atp2a2 protein, rat; D009840:Oligomycins; D010042:Ouabain; D000244:Adenosine Diphosphate; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase; D011770:Pyruvate Kinase; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D012966:Sodium Cyanide