title: Adenylyl cyclase type V deletion increases basal left ventricular function and reduces left ventricular contractile responsiveness to beta-adrenergic stimulation.
abstract: We tested the hypothesis that deletion of adenylyl cyclase type V (AC(V)) would be associated with decreased left ventricular (LV) contractile function and responsiveness to beta-adrenergic receptor (betaAR) stimulation. Absence of cardiac AC(V) expression was confirmed by RT-PCR and immunoblotting in AC(V)-deleted mice (AC(V) (-/-)). Compared to sibling mice with normal amounts of AC(V) (CON), basal and water-soluble forskolin derivative NKH477-stimulated cAMP production was reduced in both LV homogenates and in isolated cardiac myocytes. Basal LV +dP/dt (isolated perfused hearts) was increased (CON: 3,649 +/- 247 mmHg/s; AC(V) (-/-): 4,625 +/- 350 mmHg/s; p = 0.035, n = 10), but the potency of dobutamine on LV +dP/dt was decreased by AC(V) deletion (log EC(50): CON: -6.83 +/- 0.14 M; AC(V) (-/-): -5.99 +/- 0.15 M; p = 0.0007, n = 10). The initial rates of ATP-dependent sarcoplasmic reticulum calcium uptake, assessed in LV homogenates, showed that AC(V) deletion increased SERCA2a affinity for Ca(2+) (log EC(50): CON: -5.94 +/- 0.03 M; AC(V) (-/-): -6.09 +/- 0.02 M; p = 0.001, n = 8). AC(V) deletion is also associated with increased phospholamban phosphorylation, decreased type 1 protein phosphatase catalytic subunit content and activity, and reduced cardiac Galphas protein content. In conclusion, AC(V) deletion has a favorable effect on basal LV function despite reduced cAMP levels. Increased SERCA2a affinity for Ca(2+) and increased phospholamban phosphorylation are contributing factors. However, AC(V) deletion is associated with reduced LV contractile responsiveness to betaAR stimulation, an effect that is associated with reduced Galphas protein content and reduced cAMP generating capacity in cardiac myocytes.
authors.affiliation: Veterans Affairs, San Diego Healthcare System, 9151A, 3350 La Jolla Village Drive, San Diego, California 92161, USA. ttang@vapop.ucsd.edu
authors.forename: Tong
authors.initials: T
authors.lastname: Tang
authors.forename: N Chin
authors.initials: NC
authors.lastname: Lai
authors.forename: David M
authors.initials: DM
authors.lastname: Roth
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Drumm
authors.forename: Tracy
authors.initials: T
authors.lastname: Guo
authors.forename: Ko-Woon
authors.initials: KW
authors.lastname: Lee
authors.forename: Pyung-Lim
authors.initials: PL
authors.lastname: Han
authors.forename: Nancy
authors.initials: N
authors.lastname: Dalton
authors.forename: Mei Hua
authors.initials: MH
authors.lastname: Gao
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics* / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004452:Echocardiography; D019204:GTP-Binding Proteins / Q000378:metabolism; D017353:Gene Deletion; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D009924:Organ Culture Techniques; D018342:Receptors, Adrenergic, beta-1 / Q000187:drug effects / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D016277:Ventricular Function, Left / Q000502:physiology*; D000099211:Phospholamban
chemical_list: D000262:Adenylyl Cyclases; D000318:Adrenergic beta-Agonists; D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D018342:Receptors, Adrenergic, beta-1; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban