Airhart Nathan, Yang Yong-Feng, Roberts Charles T, Silberbach Michael
Department of Pediatrics and the Heart Research Center, Oregon Health and Science University, Portland, Oregon 97239, USA.
J Biol Chem. 2003 Oct 3;278(40):38693-8. doi: 10.1074/jbc.M304098200. Epub 2003 Jul 10.
Circulating natriuretic peptides such as atrial natriuretic peptide (ANP) counterbalance the effects of hypertension and inhibit cardiac hypertrophy by activating cGMP-dependent protein kinase (PKG). Natriuretic peptide binding to type I receptors (NPRA and NPRB) activates their intrinsic guanylyl cyclase activity, resulting in a rapid increase in cytosolic cGMP that subsequently activates PKG. Phosphorylation of the receptor by an unknown serine/threonine kinase is required before ligand binding can activate the cyclase. While searching for downstream PKG partners using a yeast two-hybrid screen of a human heart cDNA library, we unexpectedly found an upstream association with NPRA. PKG is a serine/threonine kinase capable of phosphorylating NPRA in vitro; however, regulation of NPRA by PKG has not been previously reported. Here we show that PKG is recruited to the plasma membrane following ANP treatment, an effect that can be blocked by pharmacological inhibition of PKG activation. Furthermore, PKG participates in a ligand-dependent gain-of-function loop that significantly increases the intrinsic cyclase activity of the receptor. PKG translocation is ANP-dependent but not nitric oxide-dependent. Our results suggest that anchoring of PKG to NPRA is a key event after ligand binding that determines distal effects. As such, the NPRA-PKG association may represent a novel mechanism for compartmentation of cGMP-mediated signaling and regulation of receptor sensitivity.
循环利钠肽，如心房利钠肽（ANP），可对抗高血压的影响，并通过激活环磷酸鸟苷（cGMP）依赖性蛋白激酶（PKG）来抑制心肌肥大。利钠肽与I型受体（NPRA和NPRB）结合可激活其内在的鸟苷酸环化酶活性，导致胞质cGMP迅速增加，随后激活PKG。在配体结合激活环化酶之前，需要一种未知的丝氨酸/苏氨酸激酶对受体进行磷酸化。在用人心脏cDNA文库进行酵母双杂交筛选以寻找下游PKG伴侣时，我们意外地发现了PKG与NPRA的上游关联。PKG是一种能够在体外磷酸化NPRA的丝氨酸/苏氨酸激酶；然而，此前尚未报道PKG对NPRA的调节作用。在这里，我们表明，ANP处理后PKG被招募到质膜，这一效应可被PKG激活的药理学抑制所阻断。此外，PKG参与了一个配体依赖性的功能获得环，该环显著增加了受体的内在环化酶活性。PKG易位依赖于ANP而非一氧化氮。我们的结果表明，PKG与NPRA的锚定是配体结合后决定远端效应的关键事件。因此，NPRA-PKG关联可能代表了一种cGMP介导信号传导分隔和受体敏感性调节的新机制。
