Dynamic regulation of phosphoinositide 3-kinase-gamma activity and beta-adrenergic receptor trafficking in end-stage human heart failure

Article

关键词: ASSIST DEVICE SUPPORT;    PROTEIN-COUPLED RECEPTORS;    FAILING HUMAN HEARTS;    VENTRICULAR-FUNCTION;    DOWN-REGULATION;    LVAD;    INHIBITION;    RESTORATION;    RECRUITMENT;    SENSITIVITY;   

DOI  :  10.1161/CIRCULATIONAHA.107.706515

来源: SCIE

【 摘 要 】

Background-Downregulation of beta-adrenergic receptors (beta ARs) under conditions of heart failure requires receptor targeting of phosphoinositide 3-kinase (PI3K)-gamma and redistribution of beta ARs into endosomal compartments. Because support with a left ventricular assist device (LVAD) results in significant improvement of cardiac function in humans, we investigated the effects of mechanical unloading on regulation of PI3K gamma activity and intracellular distribution of beta ARs. Additionally, we tested whether displacement of PI3K gamma from activated beta ARs would restore agonist responsiveness in failing human cardiomyocytes. Methods and Results-To test the role of PI3K on beta AR endocytosis in failing human hearts, we assayed for PI3K activity in human left ventricular samples before and after mechanical unloading (LVAD). Before LVAD, failing human hearts displayed a marked increase in beta AR kinase 1 (beta ARK1)-associated PI3K activity that was attributed exclusively to enhanced activity of the PI3K gamma isoform. Increased beta ARK1-coupled PI3K activity in the failing hearts was associated with downregulation of beta ARs from the plasma membrane and enhanced sequestration into early and late endosomes compared with unmatched nonfailing controls. Importantly, LVAD support reversed PI3K gamma activation, normalized the levels of agonist-responsive beta ARs at the plasma membrane, and depleted the beta ARs from the endosomal compartments without changing the total number of receptors (sum of plasma membrane and early and late endosome receptors). To test whether the competitive displacement of PI3K from the beta AR complex restored receptor responsiveness, we overexpressed the phosphoinositide kinase domain of PI3K (which disrupts beta ARK1/PI3K interaction) in primary cultures of failing human cardiomyocytes. Adenoviral-mediated phosphoinositide kinase overexpression significantly increased basal contractility and rapidly reconstituted responsiveness to beta-agonist. Conclusions-These results suggest a novel paradigm in which human beta ARs undergo a process of intracellular sequestration that is dynamically reversed after LVAD support. Importantly, mechanical unloading leads to complete reversal in PI3K gamma and beta ARK1-associated PI3K activation. Furthermore, displacement of active PI3K from beta ARK1 restores beta AR responsiveness in failing myocytes.

【 授权许可】

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