PTEN-dependent regulation of SRF transcriptional activity and SMC phenotype control

SRF 转录活性的 PTEN 依赖性调节和 SMC 表型控制

• 批准号: 9247031
• 负责人: Mary Cm. Weiser-Evans
• 金额: $ 49.55万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-05 至 2019-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9247031
• 关键词: AKT Signaling Pathway; Acute; Angioplasty; Animals; Arterial Fatty Streak; Arteries; Atherosclerosis; Binding; Biological Assay; Blood Vessels; Cardiac Myocytes; Cell Nucleus; Cells; Characteristics; Chronic; Clinical; Complex; Contractile Proteins; Coronary artery; Data; Disease; Disease Progression; EMSA; Elements; Epigenetic Process; Event; Exclusion; Feedback; Gene Expression; Gene Expression Regulation; Genes; Genetic; Genetic Models; Genetic Transcription; Growth; HIF1A gene; Human; Immediate-Early Genes; In Situ; In Vitro; Inflammation; Inflammation Mediators; Inflammatory; Injury; Knockout Mice; Lesion; Link; Lipids; Maintenance; MicroRNAs; Modeling; Molecular; Multiprotein Complexes; Mus; Muscle Cells; Nuclear; PTEN gene; Pathologic; Pathway interactions; Phenotype; Phosphoric Monoester Hydrolases; Physiological; Play; Post-Translational Protein Processing; Procedures; Production; Protein phosphatase; Proteins; Publishing; Recruitment Activity; Regulation; Role; Serum Response Factor; Signaling Molecule; Smooth Muscle Myocytes; Specimen; Stents; Stimulus; Testing; Transcriptional Regulation; Vascular Diseases; Vascular Smooth Muscle; Vascular remodeling; arterial lesion; autocrine; cell type; human disease; innovation; macrophage; mouse model; myocardin; novel; novel therapeutics; overexpression; pre-clinical; preclinical study; prevent; promoter; protein expression; public health relevance; response; restenosis; transcription factor

 DESCRIPTION (provided by applicant): A unique characteristic of resident vascular smooth muscle cells (SMCs) and a hallmark of vascular disease progression is SMC phenotypic switching marked by a change in SMC phenotype. Regulation of PTEN, a lipid and protein phosphatase that predominantly inhibits cytoplasmic PI3K/Akt activity, is critical in pathological vascular remodeling. PTEN represses SMC phenotypic switching while its loss results in decreased SM contractile gene expression and increased proliferation and production inflammatory mediators. Enhanced proliferation and inflammatory mediator production are dependent on loss of PTEN's phosphatase activity and consequent increased Akt activity. However, since SM genes are under direct transcriptional control by serum response factor (SRF), the mechanism underlying PTEN's regulation of SM gene expression remained unclear and is the focus of this proposal. Under physiological conditions, SMCs express a quiescent, differentiated phenotype, characterized by high expression of SRF-dependent SM genes. SRF is a ubiquitous and essential transcription factor that binds CArG elements in SM genes. Paradoxically, SRF also regulates immediate early genes. Control of SM gene expression by SRF involves interactions between SRF and cell-specific co- activators, epigenetic control of gene expression, and regulation of SRF through post-translational modifications and spatial/temporal changes. Our new published and preliminary data show a direct link between PTEN and SRF in this regulation. Our published studies demonstrated that PTEN is a downstream effector of SRF through a microRNA (miRNA)-dependent pathway. Loss of this axis promotes reprogramming to a proliferative, inflammatory phenotype. To support this current project, new preliminary data suggest a novel upstream function for nuclear PTEN that is independent of its phosphatase activity. We demonstrate direct interaction of PTEN with SRF, which facilitates SRF-dependent SM gene transcription suggesting a positive feedback loop involving PTEN and SRF. Pathophysiologic or genetic loss of PTEN results in loss of SRF binding to SM gene promoters and SMC phenotypic switching. Clinically, loss of nuclear PTEN and overall decreased expression is observed in intimal SMCs of human atherosclerotic lesions, supporting a critical role for nuclear PTEN in regulation of lesion progression. We propose a positive feedback loop between PTEN and SRF underlies maintenance of a differentiated, quiescent SMC phenotype. We hypothesize that physiologic or pathologic stimuli induce nuclear exclusion of PTEN and SRF with subsequent inhibition of SRF- dependent SM gene transcription and dysregulation of the SRF-miRNA-PTEN network controlling proliferation and inflammation. We will define the molecular mechanisms underlying PTEN regulation of SRF transcriptional activity (Aim One), establish the importance of PTEN-dependent regulation of SRF transcriptional activity using complex genetic mouse models of atherosclerosis and vascular injury (Aim Two), and establish the significance of nuclear PTEN on SMC phenotype in normal and diseased human arteries (Aim Three).

 描述（由申请人提供）：驻留血管平滑肌细胞（SMC）的独特特征和血管疾病进展的标志是SMC表型转换，其特征在于SMC表型的变化。 PTEN 是一种脂质和蛋白磷酸酶，主要抑制细胞质 PI3K/Akt 活性，其调节在病理性血管重塑中至关重要。 PTEN 抑制 SMC 表型转换，而其缺失会导致 SM 收缩基因表达减少、增殖和炎症介质产生增加。增殖和炎症介质产生的增强取决于 PTEN 磷酸酶活性的丧失以及随之而来的 Akt 活性的增加。然而，由于 SM 基因受到血清反应因子 (SRF) 的直接转录控制，因此 PTEN 调节 SM 基因表达的机制仍不清楚，也是本提案的重点。在生理条件下，SMC 表达静态、分化的表型，其特征是 SRF 依赖性 SM 基因的高表达。 SRF 是一种普遍存在且必需的转录因子，可结合 SM 基因中的 CArG 元件。矛盾的是，SRF 还调节即早期基因。 SRF对SM基因表达的控制涉及SRF和细胞特异性共激活剂之间的相互作用、基因表达的表观遗传控制以及通过翻译后修饰和空间/时间变化对SRF的调节。我们新发布的初步数据显示，该法规中 PTEN 和 SRF 之间存在直接联系。我们发表的研究表明，PTEN 通过 microRNA (miRNA) 依赖性途径成为 SRF 的下游效应子。该轴的丧失会促进重编程为增殖性炎症表型。为了支持当前的项目，新的初步数据表明核 PTEN 具有独立于其磷酸酶活性的新上游功能。我们证明了 PTEN 与 SRF 的直接相互作用，这促进了 SRF 依赖性 SM 基因转录，表明涉及 PTEN 和 SRF 的正反馈循环。 PTEN 的病理生理或遗传缺失会导致 SRF 与 SM 基因启动子的结合丧失以及 SMC 表型转换。临床上，在人类动脉粥样硬化病变的内膜 SMC 中观察到核 PTEN 缺失和整体表达下降，支持核 PTEN 在调节病变进展中的关键作用。我们提出 PTEN 和 SRF 之间的正反馈循环是维持分化的静态 SMC 表型的基础。我们假设生理或病理刺激诱导 PTEN 和 SRF 的核排斥，随后抑制 SRF 依赖性 SM 基因转录以及控制增殖和炎症的 SRF-miRNA-PTEN 网络失调。我们将定义 PTEN 调节 SRF 转录活性的分子机制（目标一），利用动脉粥样硬化和血管损伤的复杂遗传小鼠模型确定 PTEN 依赖性调节 SRF 转录活性的重要性（目标二），并确定核 PTEN 对正常和患病人类动脉 SMC 表型的重要性（目标三）。