Phospholamban knockout increases CaM kinase II activity and intracellular Ca2+ wave activity and alters contractile responses of murine gastric antrum.
Phospholamban (PLB) inhibits the sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA), and this inhibition is relieved by Ca(2+) calmodulin-dependent protein kinase II (CaM kinase II) phosphorylation. We previously reported significant differences in contractility, SR Ca(2+) release, and CaM kinase II activity in gastric fundus smooth muscles as a result of PLB phosphorylation by CaM kinase II. In this study, we used PLB-knockout (PLB-KO) mice to directly examine the effect of PLB absence on contractility, CaM kinase II activity, and intracellular Ca(2+) waves in gastric antrum smooth muscles. The frequencies and amplitudes of spontaneous phasic contractions were elevated in antrum smooth muscle strips from PLB-KO mice. Bethanecol increased the amplitudes of phasic contractions in antrum smooth muscles from both control and PLB-KO mice. Caffeine decreased and cyclopiazonic acid (CPA) increased the basal tone of antrum smooth muscle strips from PLB-KO mice, but the effects were less pronounced compared with control strips. The CaM kinase II inhibitor KN-93 was less effective at inhibiting caffeine-induced relaxation in antrum smooth muscle strips from PLB-KO mice. CaM kinase II autonomous activity was elevated, and not further increased by caffeine, in antrum smooth muscles from PLB-KO mice. Similarly, the intracellular Ca(2+) wave frequency was elevated, and not further increased by caffeine, in antrum smooth muscles from PLB-KO mice. These findings suggest that PLB is an important modulator of gastric antrum smooth muscle contractility by modulation of SR Ca(2+) release and CaM kinase II activity.
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
Minkyung
M
Kim
Grant W
GW
Hennig
Terence K
TK
Smith
Brian A
BA
Perrino
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D020013:Calcium Signaling / Q000235:genetics*; D002135:Calcium-Binding Proteins / Q000235:genetics*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007424:Intracellular Fluid / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000187:drug effects / Q000235:genetics*; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology*; D010528:Peristalsis / Q000187:drug effects / Q000235:genetics; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011706:Pyloric Antrum / Q000187:drug effects / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D000099211:Phospholamban
D002110:Caffeine; D002135:Calcium-Binding Proteins; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D004791:Enzyme Inhibitors; D007211:Indoles; D010726:Phosphodiesterase Inhibitors; D000099211:Phospholamban; C000543:cyclopiazonic acid