%0 Journal Article %1 Berr_2007_92 %A Berry, Roger G %A Despa, Sanda %A Fuller, William %A Bers, Donald M %A Shattock, Michael J %D 2007 %J Cardiovasc. Res. %K AMP-Dependent ATPase, Adrenergic Animals; C57BL; Cardiac, Confocal; Cyclic Fibers, Formamides; Heart Inbred Isoenzymes, Isoproterenol, Kinases, Mice, Mice; Microscopy, Muscle Myocytes, Patch-Clamp Protein Sarcolemma, Sodium, Sodium-Potassium-Exchanging Techniques; Ventricles; analysis/metabolism analysis/metabolism; beta-Agonists, enzymology/ultrastructure; enzymology; metabolism; pharmacology; %N 1 %P 92--100 %R 10.1016/j.cardiores.2006.11.006 %T Differential distribution and regulation of mouse cardiac Na$^+$/K$^+$-ATPase alpha1 and alpha2 subunits in T-tubule and surface sarcolemmal membranes. %U http://dx.doi.org/10.1016/j.cardiores.2006.11.006 %V 73 %X OBJECTIVES: Two Na$^+$/K$^+$-ATPase (NKA) alpha-subunit isoforms, alpha1 and alpha2, are expressed in the adult mouse heart. The subcellular distribution of these isoforms in T-tubule and surface sarcolemmal (SSL) membranes and their regulation by cAMP-dependent protein kinase (PKA) is unclear. METHODS: We used formamide-induced detubulation of mouse ventricular myocytes to investigate differential functional distribution and regulation by PKA of alpha1 and alpha2 in T-tubule versus SSL membranes by measuring NKA current (I(pump)) and NKA-mediated Na$^+$ efflux (-dNa(i)/dt). RESULTS: I(pump) is composed of 88\% alpha(1)-mediated I(pump) (Ialpha1) and 12\% alpha2-mediated I(pump) (Ialpha2). alpha1 and alpha2 subunits demonstrate distinct ouabain affinities (105+/-6 and 0.3+/-0.1 micromol/L respectively) but similar affinity for intracellular Na$^+$ (K(1/2)Na$^+$ of 16.6+/-0.8 and 16.7+/-2.6 mmol/L respectively). Detubulation reduced (i) I(pump) density (1.42+/-0.1 to 1.20+/-0.04 pA/pF), (ii) cell capacitance (181+/-12 to 127+/-17 pF), and (iii) Ialpha2 contribution (12 to 6\%). Total I(pump) density was approximately 60\% higher in T-tubule (1.94 pA/pF, derived) vs. SSL membranes. Although T-tubule membranes represent only 30\% of total surface area, they generate approximately 70\% of Ialpha2 and approximately 37\% of Ialpha1. Ialpha1 density was substantially higher than Ialpha2 in SSL (Ialpha1:Ialpha2 = 16:1) but this was markedly reduced in T-tubules (4:1). In addition to differential localisation, isoprenaline (ISO, 1 micromol/L) significantly increased alpha1-mediated NKA Na$^+$ affinity (from 16.6+/-0.8 to 13.3+/-1.4 mmol/L) and caused a small increase in maximal NKA Na$^+$ efflux rate. ISO had no effect on alpha2-mediated NKA activity. CONCLUSION: These data suggest that NKA alpha1 and alpha2 subunits are differentially localised and regulated by PKA in T-tubule and SSL membranes and may have distinct regulatory roles in cardiac excitation-contraction coupling.

@article{Berr_2007_92, abstract = {OBJECTIVES: Two {N}a$^{+}$/{K}$^{+}$-ATPase (NKA) alpha-subunit isoforms, alpha1 and alpha2, are expressed in the adult mouse heart. The subcellular distribution of these isoforms in T-tubule and surface sarcolemmal (SSL) membranes and their regulation by cAMP-dependent protein kinase (PKA) is unclear. METHODS: We used formamide-induced detubulation of mouse ventricular myocytes to investigate differential functional distribution and regulation by PKA of alpha1 and alpha2 in T-tubule versus SSL membranes by measuring NKA current (I(pump)) and NKA-mediated {N}a$^{+}$ efflux (-d[Na](i)/dt). RESULTS: I(pump) is composed of 88\% alpha(1)-mediated I(pump) (Ialpha1) and 12\% alpha2-mediated I(pump) (Ialpha2). alpha1 and alpha2 subunits demonstrate distinct ouabain affinities (105+/-6 and 0.3+/-0.1 micromol/L respectively) but similar affinity for intracellular {N}a$^{+}$ (K(1/2){N}a$^{+}$ of 16.6+/-0.8 and 16.7+/-2.6 mmol/L respectively). Detubulation reduced (i) I(pump) density (1.42+/-0.1 to 1.20+/-0.04 pA/pF), (ii) cell capacitance (181+/-12 to 127+/-17 pF), and (iii) Ialpha2 contribution (12 to 6\%). Total I(pump) density was approximately 60\% higher in T-tubule (1.94 pA/pF, derived) vs. SSL membranes. Although T-tubule membranes represent only 30\% of total surface area, they generate approximately 70\% of Ialpha2 and approximately 37\% of Ialpha1. Ialpha1 density was substantially higher than Ialpha2 in SSL (Ialpha1:Ialpha2 = 16:1) but this was markedly reduced in T-tubules (4:1). In addition to differential localisation, isoprenaline (ISO, 1 micromol/L) significantly increased alpha1-mediated NKA {N}a$^{+}$ affinity (from 16.6+/-0.8 to 13.3+/-1.4 mmol/L) and caused a small increase in maximal NKA {N}a$^{+}$ efflux rate. ISO had no effect on alpha2-mediated NKA activity. CONCLUSION: These data suggest that NKA alpha1 and alpha2 subunits are differentially localised and regulated by PKA in T-tubule and SSL membranes and may have distinct regulatory roles in cardiac excitation-contraction coupling.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Berry, Roger G and Despa, Sanda and Fuller, William and Bers, Donald M and Shattock, Michael J}, biburl = {https://www.bibsonomy.org/bibtex/21ab66dce129399136e853e247e80df7f/hake}, description = {The whole bibliography file I use.}, doi = {10.1016/j.cardiores.2006.11.006}, file = {Berr_2007_92.pdf:Berr_2007_92.pdf:PDF}, institution = {Cardiac Physiology, King's College London, The Rayne Institute, St Thomas' Hospital, London SE1 7EH, UK.}, interhash = {516c67d08a103f71f49e0c56cd01e3f5}, intrahash = {1ab66dce129399136e853e247e80df7f}, journal = {Cardiovasc. Res.}, keywords = {AMP-Dependent ATPase, Adrenergic Animals; C57BL; Cardiac, Confocal; Cyclic Fibers, Formamides; Heart Inbred Isoenzymes, Isoproterenol, Kinases, Mice, Mice; Microscopy, Muscle Myocytes, Patch-Clamp Protein Sarcolemma, Sodium, Sodium-Potassium-Exchanging Techniques; Ventricles; analysis/metabolism analysis/metabolism; beta-Agonists, enzymology/ultrastructure; enzymology; metabolism; pharmacology;}, month = Jan, number = 1, pages = {92--100}, pdf = {Berr_2007_92.pdf}, pii = {S0008-6363(06)00494-9}, pmid = {17157829}, timestamp = {2009-06-03T11:21:02.000+0200}, title = {Differential distribution and regulation of mouse cardiac {N}a$^{+}$/{K}$^{+}$-ATPase alpha1 and alpha2 subunits in T-tubule and surface sarcolemmal membranes.}, url = {http://dx.doi.org/10.1016/j.cardiores.2006.11.006}, volume = 73, year = 2007 }