title: Cyclic GMP signaling and regulation of SERCA activity during cardiac myocyte contraction.
abstract: We tested the hypothesis that cGMP-induced reductions in cardiac myocyte function were related to activation of the sarcoplasmic reticulum Ca2+-ATPase (SERCA) and cGMP-dependent phosphorylation of phospholamban. Ventricular myocyte function was measured using a video edge detector (n = 11 rabbits). Thapsigargin (TG) or cyclopiazonic acid (CPA) were used to inhibit SERCA. 8-Bromo-cGMP was added at 10(-6), 10(-5) M followed by TG 10(-8) M or KT5823 (cGMP-protein kinase inhibitor, 10(-6) M) prior to TG or CPA. Cyclic GMP-dependent protein phosphorylation and immunoblotting with anti-phospholamban antibody were examined. TG 10(-8) M significantly increased percent shortening (from 6.6+/-0.7 to 9.1+/-1.3%). Cyclic GMP 10(-5) M significantly decreased cell shortening from 9.3+/-0.9 to 5.1+/-0.6%. This was partially reversed by KT5823 (5.1+/-0.6 to 8.2+/-1.4%) suggesting that negative functional effects of cGMP were partially through the cGMP-dependent protein kinase. Addition of TG after cGMP also reduced the negative effects of cGMP on myocyte shortening suggesting involvement of SERCA in cGMP signaling. TG after cGMP and KT5823 treatment did not alter myocyte contractility (8.2+/-1.4 to 7.2+/-1.3%). CPA had similar effects as those of TG. Protein phosphorylation and immunoblotting showed that phospholamban was a target of the cGMP protein kinase. These results indicated that the cyclic GMP-induced reductions in myocyte function were partially mediated through the action of SERCA. It further suggested that cGMP signaling affects myocyte function through phosphorylation of phospholamban which regulates SERCA activity.
authors.affiliation: Heart and Brain Circulation Laboratory, Department of Physiology and Biophysics, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854-5635, USA.
authors.forename: Qihang
authors.initials: Q
authors.lastname: Zhang
authors.forename: Peter M
authors.initials: PM
authors.lastname: Scholz
authors.forename: Yiqi
authors.initials: Y
authors.lastname: He
authors.forename: James
authors.initials: J
authors.lastname: Tse
authors.forename: Harvey R
authors.initials: HR
authors.lastname: Weiss
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002227:Carbazoles / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004789:Enzyme Activation; D007211:Indoles / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology; D000099211:Phospholamban
chemical_list: D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D002227:Carbazoles; D006152:Cyclic GMP; D017869:Cyclic GMP-Dependent Protein Kinases; D007211:Indoles; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019284:Thapsigargin; D000099211:Phospholamban; C073601:KT 5823; C016276:8-bromocyclic GMP; C000543:cyclopiazonic acid