title: Role of phospholamban in cyclic GMP mediated signaling in cardiac myocytes.
abstract: We tested the hypothesis that the negative functional effects of cyclic GMP on cardiac myocytes were mediated through phospholamban (PLB) and activation of sarcoplasmic reticulum Ca(2+)-ATPase. Using ventricular myocytes from wild type (WT, n=10) and PLB knockout (PLB-KO, n=10) mouse hearts, functional changes were measured using a video edge detector at baseline and after 10(-6), 10(-5)M 8-bromo-cyclic GMP (cGMP), 10(-8), 10(-7)M C-type natriuretic peptide (CNP), or 10(-6), 10(-5)M S-nitroso-N-acetyl-penicillamine (SNAP, nitric oxide donor). Changes in cytosolic Ca(2+) concentration were assessed in fura 2-loaded WT and PLB-KO myocytes. Cyclic GMP dependent phosphorylation analysis was also performed in WT and PLB-KO myocytes. 8-bromo-cGMP 10(-5)M caused a significant decrease in %shortening (3.6+/-0.2% to 2.3+/-0.1%) in WT, but little change in PLB-KO myocytes (3.4+/-0.1% to 3.2+/-0.2%). Similarly, CNP and SNAP reduced %shortening of WT, but not PLB-KO myocyte. Changes in other contractile parameters such as maximum rate of shortening and relaxation were consistent with the changes in % shortening. Intracellular Ca(2+) transients changed similarly to cell contractility in WT and PLB-KO myocytes treated with cGMP and CNP; i.e. Ca(2+) transients decreased with cGMP or CNP in WT myocytes, but were unchanged in PLB-KO myocytes. cGMP dependent phosphorylation analysis showed that some proteins were phosphorylated by cGMP to a lesser extent in PLB-KO compared with WT myocytes, suggesting impaired cGMP-kinase function in PLB-KO cardiac myocytes. These results indicated that cGMP-induced reductions in cardiac myocyte function were at least partially mediated through the action of phospholamban.
authors.affiliation: Heart and Brain Circulation Laboratory, Department of Physiology and Biophysics, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854-8021, USA.
authors.forename: Qihang
authors.initials: Q
authors.lastname: Zhang
authors.forename: Peter M
authors.initials: PM
authors.lastname: Scholz
authors.forename: Anna
authors.initials: A
authors.lastname: Pilzak
authors.forename: Jun
authors.initials: J
authors.lastname: Su
authors.forename: Harvey R
authors.initials: HR
authors.lastname: Weiss
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D020098:Natriuretic Peptide, C-Type / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010766:Phosphorylation; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D000099211:Phospholamban
chemical_list: D002135:Calcium-Binding Proteins; D006152:Cyclic GMP; D020098:Natriuretic Peptide, C-Type; D020030:Nitric Oxide Donors; D026423:S-Nitroso-N-Acetylpenicillamine; D000099211:Phospholamban; C016276:8-bromocyclic GMP