Role of phospholamban in the modulation of arterial Ca(2+) sparks and Ca(2+)-activated K(+) channels by cAMP.
Phospholamban (PLB) inhibits the sarcoplasmic reticulum (SR) Ca(2+)-ATPase, and this inhibition is relieved by cAMP-dependent protein kinase (PKA)-mediated phosphorylation. The role of PLB in regulating Ca(2+) release through ryanodine-sensitive Ca(2+) release channels, measured as Ca(2+) sparks, was examined using smooth muscle cells of cerebral arteries from PLB-deficient ("knockout") mice (PLB-KO). Ca(2+) sparks were monitored optically using the fluorescent Ca(2+) indicator fluo 3 or electrically by measuring transient large-conductance Ca(2+)-activated K(+) (BK) channel currents activated by Ca(2+) sparks. Basal Ca(2+) spark and transient BK current frequency were elevated in cerebral artery myocytes of PLB-KO mice. Forskolin, an activator of adenylyl cyclase, increased the frequency of Ca(2+) sparks and transient BK currents in cerebral arteries from control mice. However, forskolin had little effect on the frequency of Ca(2+) sparks and transient BK currents from PLB-KO cerebral arteries. Forskolin or PLB-KO increased SR Ca(2+) load, as measured by caffeine-induced Ca(2+) transients. This study provides the first evidence that PLB is critical for frequency modulation of Ca(2+) sparks and associated BK currents by PKA in smooth muscle.
Wellman
G C
GC
Department of Pharmacology, University of Vermont, Burlington, Vermont 05405, USA.
Santana
L F
LF
Bonev
A D
AD
Nelson
M T
MT
D000814:Aniline Compounds; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D002536:Cerebral Arteries / Q000187:drug effects / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D051036:Large-Conductance Calcium-Activated Potassium Channels; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D012433:Ryanodine / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D014966:Xanthenes; D000099211:Phospholamban
D000814:Aniline Compounds; D002110:Caffeine; D002118:Calcium; D002135:Calcium-Binding Proteins; D005576:Colforsin; D000242:Cyclic AMP; D004791:Enzyme Inhibitors; D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D012433:Ryanodine; D013873:Thionucleotides; D014966:Xanthenes; D000099211:Phospholamban; C059715:Fluo-3; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP