Dissecting GRK Function in the Heart

越来越清楚的是，G蛋白偶联受体（GPCR）激酶（GRKs）在细胞凋亡中起着关键作用。 调节心肌信号和功能。GRKs磷酸化激动剂占据的GPCR触发 脱敏的过程，导致下游信号的丢失。GRK对GPCR的行动 促进B-抑制蛋白与受体结合，从而导致受体内化和再敏感化 作为新的信号级联的激活。如本项目规划第一个供资周期所述， 和B-抑制蛋白似乎通过下游的信号系统在心脏中发挥新的作用。 脱敏的GPCR。GRK 2是心肌中表达最丰富的GRK同种型， 在过去的15年里，我们与Rockman博士和Lefkowitz博士密切合作，发现了一个明显的结果 GRK 2通过其对β-肾上腺素能受体（PAR）信号传导的调节控制在衰竭心脏中的重要性。 我们最近在PPG中的数据已经阐明GRK 2可能对心脏信号传导有影响， 不仅通过调节BAR介导的收缩功能，而且通过独特的细胞内 靶点，包括改变慢性心力衰竭（HF）进展的细胞存活途径。与此相一致， 本提案中将提供数据，证明GRK 2可以增加心肌细胞凋亡， 缺血性损伤此外，我们目前的数据显示GRK 2存在于线粒体中，并具有独特的生物学特性。 与一氧化氮合酶（NOS）和一氧化氮（NO）的关系。这包括与以下机构的合作发现： 这个PPG组的成员首次表明GRK 2可以被S-亚硝基化。似乎没有 生物利用度调节GRK 2对BAR的活性。因此，通过新的蛋白质-蛋白质相互作用或 通过独特的细胞定位和调节，GRK 2似乎具有对正常细胞生长至关重要的多功能。 心脏应激时的心脏功能和适应，特别是缺血性损伤，可导致HF。在这 项目，GRK 2在心脏中的新颖方面将被探索，这是相互关联的，并与 其他项目集中在肌细胞PAR信号传导，其通过其他GRKs和B-抑制蛋白功能的调节， 调控该项目也将得到该PPG内科学核心的极大帮助。我们的中央 假设GRK 2在心脏的信号传导和生理学中起着重要作用， 在受损和受损的心肌中至关重要，尤其是在缺血后。这包括肾上腺素能以外的作用 依赖性收缩功能，并涉及新的GRK调节，细胞定位和下游 目标的本研究的具体目的是：（1）探讨GRK 2在脑缺血再灌注损伤中的作用机制 心肌缺血性损伤包括心肌细胞存活;（2）研究GRK 2- 一氧化氮合酶（NOS）和NO在心脏中的连锁和机制关系;（3）确定 S-亚硝基化的生理作用及其对GRK 2及其在心脏中的活性的调节。

It is becoming increasingly clear that G protein-coupled receptor (GPCR) kinases (GRKs) play a critical role in modulating myocardial signaling and function. GRKs phosphorylate agonist-occupied GPCRs triggering the process of desensitization, leading to the loss of down-stream signaling. GRK action on GPCRs promotes B-arrestin binding to receptors, which leads to receptor internalization and resensitization as well as activation of novel signaling cascades. As delineated during the first funding cycle of this PPG, GRKs and B-arrestins appear to have novel actions in the heart through signaling systems that are down-stream of desensitized GPCRs. GRK2 is the most abundant GRK isoform expressed in myocardium and through our close collaboration with Drs. Rockman and Lefkowitz over the last 15 years, we have uncovered a clear importance of GRK2 in the failing heart via its regulatory control on p-adrenergic receptor (PAR) signaling. Recent data by us within this PPG has elucidated that GRK2 may have influences on cardiac signaling and function not only through regulation of BAR-mediated contractile function but also through unique cellular targets, including cell survival pathways altering progression of chronic heart failure (HF). Consistent with this, data will be presented in this proposal demonstrating that GRK2 can increase myocardial apoptosis after ischemic injury. Moreover, we present data showing that GRK2 is present in mitochondria and has a unique relationship with nitric oxide synthase (NOS) and nitric oxide (NO). This includes the collaborative finding with members of this PPG group showing, for the first time, that GRK2 can be S-nitrosylated. It appears that NO bioavailability regulates GRK2's activity towards BARs. Therefore, through novel protein-protein interactions or through unique cellular localization and regulation, GRK2 appears to have multi-functions critical for normal cardiac function and adaptation during cardiac stress, especially ischemic injury, which can lead to HF. In this Project, novel aspects of GRK2 in the heart will be explored, which is inter-related and complemented by the other projects focused on myocyte PAR signaling, its regulation by other GRKs and B-arrestin function and regulation. This Project will also be greatly aided by the scientific Cores within this PPG. Our Central Hypothesis is that GRK2 plays important roles in the signaling and physiology of the heart that becomes critical in injured and compromised myocardium, especially after ischemia. This includes effects beyond padrenergic dependent contractile function and involves novel GRK regulation, cellular localization and downstream targets. The Specific Aims are: (1) To determine the mechanistic role of GRK2 in the pathophysiology of myocardial ischemic injury including myocyte survival; (2) To investigate the in vivo significance of a GRK2 - nitric oxide synthase (NOS) and NO linkage and mechanistic relationship in the heart; and (3) To determine the physiological role of S-nitrosylation and its regulation of GRK2 and its activity in the heart.