Exercise-induced regulation of phospholemman (FXYD1) in rat skeletal muscle: implications for Na+/K+-ATPase activity

TY - JOUR

T1 - Exercise-induced regulation of phospholemman (FXYD1) in rat skeletal muscle: implications for Na+/K+-ATPase activity

AU - Rasmussen, M K

AU - Kristensen, M

AU - Juel, C

N1 - Keywords: Animals; Blotting, Western; Caveolin 3; Cell Membrane; Chemical Fractionation; Immunoprecipitation; Male; Membrane Proteins; Muscle, Skeletal; Phosphoproteins; Phosphorylation; Physical Exertion; Protein Transport; Random Allocation; Rats; Rats, Wistar; Sarcolemma; Sodium-Potassium-Exchanging ATPase

PY - 2008

Y1 - 2008

N2 - BACKGROUND: Na(+)/K(+)-ATPase activity is upregulated during muscle exercise to maintain ionic homeostasis. One mechanism may involve movement of alpha-subunits to the outer membrane (translocation). AIM: We investigated the existence of exercise-induced translocation and phosphorylation of phospholemman (PLM, FXYD1) protein in rat skeletal muscle and exercise-induced changes in V(max) and K(m) for Na(+) of the Na(+)/K(+)-ATPase. METHODS: Two membrane fractionation methods and immunoprecipitation were used. Results: Both fractionation methods revealed a 200-350% increase in PLM in the sarcolemma after 30 min of treadmill running, while the phosphorylation of Ser-68 of PLM appeared to be unchanged. Exercise did not change V(max) or K(m) for Na(+) of the Na(+)/K(+)-ATPase in muscle homogenate, but induced a 67% increase in V(max) in the sarcolemmal giant vesicle preparation; K(m) for Na(+) remained constant. The main part of the increase in V(max) is related to a 36-53% increase in the level of alpha-subunits; the remainder may be related to increased PLM content. Similar results were obtained with another membrane purification method. In resting muscle, 29% and 32% of alpha(1)- and alpha(2)-subunits, respectively, were co-immunoprecipitated by PLM antibodies. In muscle homogenate prepared after exercise, immunoprecipitation of alpha(1)-subunits was increased to 227%, whereas the fraction of precipitated alpha(2) remained constant. CONCLUSION: Exercise translocates PLM to the muscle outer membrane and increases its association with mainly the alpha(1)-subunit, which may contribute to the increased V(max) of the Na(+)/K(+)-ATPase.

AB - BACKGROUND: Na(+)/K(+)-ATPase activity is upregulated during muscle exercise to maintain ionic homeostasis. One mechanism may involve movement of alpha-subunits to the outer membrane (translocation). AIM: We investigated the existence of exercise-induced translocation and phosphorylation of phospholemman (PLM, FXYD1) protein in rat skeletal muscle and exercise-induced changes in V(max) and K(m) for Na(+) of the Na(+)/K(+)-ATPase. METHODS: Two membrane fractionation methods and immunoprecipitation were used. Results: Both fractionation methods revealed a 200-350% increase in PLM in the sarcolemma after 30 min of treadmill running, while the phosphorylation of Ser-68 of PLM appeared to be unchanged. Exercise did not change V(max) or K(m) for Na(+) of the Na(+)/K(+)-ATPase in muscle homogenate, but induced a 67% increase in V(max) in the sarcolemmal giant vesicle preparation; K(m) for Na(+) remained constant. The main part of the increase in V(max) is related to a 36-53% increase in the level of alpha-subunits; the remainder may be related to increased PLM content. Similar results were obtained with another membrane purification method. In resting muscle, 29% and 32% of alpha(1)- and alpha(2)-subunits, respectively, were co-immunoprecipitated by PLM antibodies. In muscle homogenate prepared after exercise, immunoprecipitation of alpha(1)-subunits was increased to 227%, whereas the fraction of precipitated alpha(2) remained constant. CONCLUSION: Exercise translocates PLM to the muscle outer membrane and increases its association with mainly the alpha(1)-subunit, which may contribute to the increased V(max) of the Na(+)/K(+)-ATPase.

U2 - 10.1111/j.1748-1716.2008.01857.x

DO - 10.1111/j.1748-1716.2008.01857.x

M3 - Journal article

C2 - 18373741

SN - 1748-1708

VL - 194

SP - 67

EP - 79

JO - Acta Physiologica

JF - Acta Physiologica

IS - 1

ER -