Abstract 18402: Pin1 Determines beta-ARs Response to Agonist by Modulating Ca2+ Handling in Cardiomyocytes
Introduction: Chronic adrenergic system activation is characteristic of patients undergoing heart failure (HF), resulting in maladaptive remodeling to improve cardiac function. Efficacy of current medication is limited; therefore, elucidating mechanisms leading to HF upon beta (β)-ARs overdrive is critical for development of new therapies. The peptidyl-prolyl isomerase 1 (Pin1) regulates amplitude and duration of molecular signaling by promoting cis to trans isomerization of target proteins upon phosphorylation. A target negatively regulated by Pin1 is the G- protein coupled receptor kinase GRK-2 that promotes β-ARs desensitization within milliseconds upon activation to diminish receptor response to continuous or repeated stimulation.
Hypothesis: Pin1 promotes β-ARs responsiveness in the heart, whereas loss of Pin1 signaling protects from catecholamine overdrive by upregulating GRK2 and promoting β-ARs desensitization.
Methods: Adrenergic stimulation was induced by injecting isoproterenol (ISO) to act as β1/β2-ARs agonist. Hearts from “wild type” (WT) control mice as well as mice genetically modified for deletion of Pin1 (Pin1KO) were harvested and processed to analyze protein expression/ localization by immunoblot as well as immunohistochemistry. Ex-vivo functional response to escalating doses of ISO was measured using isolated WT and Pin1KO hearts by Langendorff perfusion.
Results: Pin1 activity was essential to survive adrenergic challenge as evidenced by acute lethality in Pin1KO mice after ISO injection. Pin1KO hearts show increased expression of GRK2, NCX-1 and Serca2a proteins (respectively ≈2.5, ≈4.6 and ≈3.6) compared to WT, whereas β1/β2-ARs expression was not affected. These data indicates that Pin1KO mice have impaired Ca2+ handling causing HF after ISO injection. Pin1 deletion reduced dose-dependent increases in dP/dT in response to escalating isoproterenol challenge consistent with diastolic dysfunction.
Conclusions: Pin1KO mice exhibit acute cardiac-dependent lethality following isoproterenol stress, likely due to arrhythmogenic events prompted by defective Ca2+ handling. Molecular mechanisms of Ca2+ influx/efflux after β-ARs agonist-stimulation are novel targets for Pin1-mediated regulation.
Author Disclosures: V. Sacchi: None. D.A. Kubli: None. J. Jin: None. N. Hariharan: None. C. Glembotski: None. M. Sussman: None.
- © 2016 by American Heart Association, Inc.