b1AR-mediated EGFR transactivation in the heart

 描述（由申请人提供）：心力衰竭 (HF) 是一种进行性疾病，影响着美国数百万人，每年花费数十亿美元来治疗这些患者。虽然使用神经激素受体拮抗剂（如 β 受体阻滞剂）减少了患者的症状和死亡率，但它们对心脏重塑和患者寿命的长期影响有限。一段时间以来，G 蛋白偶联受体 (GPCR) 信号传导途径已被证明是可调节的，其中可以通过偏向配体选择保护性途径（通常依赖于 β-arrestin），同时抑制有害途径（通常依赖于 G 蛋白）。然而，令人失望的是，在β-肾上腺素能受体（βAR）偏向配体的开发方面缺乏进展，尤其是β-肾上腺素能受体（βAR）的偏向配体已被证明可以通过表皮生长因子受体（EGFR）的β-抑制蛋白依赖性反式激活来传递心脏保护结果。在过去的几年中，我们广泛地表征了β1AR刺激后心肌细胞和整个心脏中急性和慢性EGFR反式激活所发生的亚细胞信号传导、转录和心脏重塑反应。我们的研究强调了 β1AR 介导的 EGFR 反式激活的潜在治疗益处，并为其作为心力衰竭治疗策略的追求提供了理论依据，但缺乏特定工具阻碍了确定性研究的执行。特别是，真正的 β1AR 特异性 βarr/EGFR 偏向配体 具有增强功效且不影响 G 蛋白依赖性信号传导的药物并不存在。因此，迄今为止的 EGFR 反式激活研究依赖于 βAR 刺激下的 EGFR 抑制来间接测量其对心肌细胞/心脏信号传导、转录和生存结果的影响。此外，EGFR 基因敲除动物无法存活，因此无法在不使用引入选择性和毒性问题的药物抑制剂的情况下评估成人心力衰竭模型中的 EGFR 功能。考虑到这些问题， 我们已经开始测试 pepducins，GPCR 细胞内环的小肽片段，它变构诱导偏向信号传导，特别是针对 β1AR，目的是在没有 G 蛋白激活的情况下驱动 EGR 反式激活。这些新的分子工具将首次对心肌细胞中 β1AR 介导的 EGFR 反式激活进行积极表征，而无需依赖药物抑制剂。此外，我们还建立了心肌细胞特异性诱导型 EGFR 缺失小鼠模型，该模型将明确确定 EGFR 信号传导对心脏响应 βAR 刺激以及更广泛形式的心力衰竭发展的影响。因此，这些研究将首次直接评估心力衰竭期间心肌细胞表达的 EGFR 的重要性，并产生新颖的潜在治疗药物，专门参与 β1AR 依赖性 EGFR 反式激活，以促进生存信号传导并减少心力衰竭期间的有害结构和功能结果。

 DESCRIPTION (provided by applicant): Heart failure (HF) is a progressive disease affecting millions of people in the U.S. with the care of these patients costing billions of dollars annually While patient symptoms and mortality have been reduced with the use of neurohormone receptor antagonists, such as β-blockers, their long-term impact on cardiac remodeling and patient lifespan is limited. G protein-coupled receptor (GPCR) signaling pathways have been shown for some time to be tunable, wherein protective pathways (often β-arrestin-dependent) may be selected for through biased ligands, while deleterious pathways (usually G protein-dependent) are simultaneously inhibited. However, there has been a disappointing lack of progress in the development of biased ligands for β- adrenergic receptors (βARs) in particular, which have been shown to relay cardioprotective outcomes via β- arrestin-dependent transactivation of epidermal growth factor receptor (EGFR). Over the last few years we have extensively characterized the subcellular signaling, transcriptional and cardiac remodeling responses that occur in response to both acute and chronic EGFR transactivation in cardiomyocytes and in whole heart following β1AR stimulation. Our studies have highlighted the potential therapeutic benefit of β1AR-mediated EGFR transactivation and provided rationale for its pursuit as a HF treatment strategy, however lack of specific tools has prevented the execution of definitive studies. In particular, bona fide β1AR-specific βarr/EGFR- biased ligands with enhanced efficacy, and that do not impact G protein-dependent signaling, do not exist. Thus, EGFR transactivation studies to date have relied upon EGFR inhibition in the presence of βAR stimulation to indirectly measure its impact on cardiomyocyte/cardiac signaling, transcription and survival outcomes. Additionally, EGFR knockout animals are not viable, thereby preventing assessment of EGFR function in adult models of HF without the use of pharmacologic inhibitors that introduce selectivity and toxicity issues. With these issues in mind, we have begun to test pepducins, small peptide fragments of the intracellular loops of GPCRs that allosterically induce biased signaling, specifically for the β1AR with the intent to drive EGR transactivation in the absence of G protein activation. These new molecular tools will allow positive characterization of β1AR-mediated EGFR transactivation in cardiomyocytes for the first time, without the reliance upon pharmacological inhibitors. Additionally, we have generated a cardiomyocyte-specific inducible EGFR deletion mouse model that will definitively establish the impact of EGFR signaling in the heart in response to βAR stimulation, as well as in the context of more broad forms of HF development. These studies will therefore provide the first direct assessment of the importance of cardiomyocyte-expressed EGFR during HF, as well as generate novel and potentially therapeutic agents with which to specifically engage β1AR-depedent EGFR transactivation to promote survival signaling and reduce detrimental structural and functional outcomes during HF.