Regulation and function of cdk5 and ezrin in senescence

cdk5和ezrin在衰老过程中的调控和功能

• 批准号: 7460620
• 负责人: Philip W. Hinds
• 金额: $ 24.97万
• 依托单位: TUFTS MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-07 至 2011-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7460620
• 关键词: Actin-Binding Protein; Actins; Affect; Attenuated; Biochemical Pathway; Biological; Cell Aging; Cell Cycle; Cell Shape; Cell physiology; Cells; Cellular Stress; Cellular biology; Cultured Cells; ERM protein; Elements; Event; Fibroblasts; Gene Expression; Genes; Genetic Transcription; Growth; Guanosine Triphosphate Phosphohydrolases; Homologous Gene; Human; Individual; Knowledge; Link; Longevity; Mediating; Membrane; Messenger RNA; Modification; Morphology; Mus; Nature; Normal Cell; Oncogene Proteins; Oncogenes; Pathway interactions; Phenotype; Phosphorylation; Primary Cell Cultures; Principal Investigator; Process; Property; Protein Overexpression; Proteins; Regulation; Reporter; Repression; Role; Shapes; Signal Transduction; Tumor Suppression; Tumor Suppressor Proteins; Withdrawal; beta-Galactosidase; cdc Genes; concept; design; ezrin; in vivo; in vivo Model; knock-down; mRNA Expression; moesin; neoplastic cell; novel; polymerization; programs; promoter; radixin protein; research study; response; senescence; tumor; tumor growth; tumorigenesis; vector

DESCRIPTION (provided by applicant): Cellular senescence is a tumor-suppressive process characterized by an irreversible cell cycle exit, a unique morphology, and expression of senescence-associated-beta-galactosidase (SA-beta-gal). Passage of normal cells in culture leads to senescence, as do cellular stresses including ras oncoprotein expression and activation of the pRb tumor suppressor pathway. Despite the potential biological importance of cellular senescence, little is known of the mechanisms leading to the senescent phenotype in cultured cells, nor is it clear to what extent these processes occur in vivo. We have recently discovered a role for cdk5 in induction of SA-beta-gal expression and senescent cytoskeletal changes. Cdk5 activity increases in senescing cells and repression of the activity of the GTPase Rac1 by cdk5 is required for expression of SA-beta-gal. Cdk5 regulation of Pad activity is also necessary for actin polymerization accompanying senescent morphology in response to expression of pRb, activated ras, or continuous passage. Inhibition of cdk5 attenuates SA-beta-gal expression and blocks actin polymerization. We have further discovered that one substrate for cdk5 in senescent cells is the ERM protein ezrin. Expression of active pRb induces expression and altered localization of ezrin, an actin-binding protein involved in membrane-cytoskeletal signaling. pRb expression results in the stimulation of cdk5-mediated phosphorylation of ezrin with subsequent membrane association and induction of cell shape changes, linking pRb activity to cytoskeletal regulation in senescent cells. These results begin to illuminate the mechanisms underlying induction of senescence and the senescent shape change and describe new pathways that may contribute to the ability of senescent cells to influence tumor growth. In order to more clearly understand the role of cdk5 and ERMs in senescence and tumor suppression, three specific aims are proposed: 1) Determine the mechanism of activation of cdk5 in senescent cells. 2) Determine how pRb activates transcription of the ezrin gene and use this information to understand transcriptional responses to pRb in senescent cells. 3) Ascertain the effects of constitutive cdk5 or ERM "knock-down" or loss on proliferation and tumorigenesis.

描述（由申请人提供）：细胞衰老是一种肿瘤抑制过程，其特征是不可逆的细胞周期出口，独特的形态和与衰老相关的β-半乳糖苷酶（SA-BETA-GAL）的表达。正常细胞在培养物中的传递会导致衰老，包括RAS癌蛋白表达和PRB肿瘤抑制途径的激活在内的细胞应激也会导致衰老。尽管细胞衰老具有潜在的生物学重要性，但对导致培养细胞中衰老表型的机制知之甚少，也不清楚这些过程在体内发生在多大程度上。我们最近发现CDK5在诱导Sa-beta-gal表达和衰老细胞骨架变化中的作用。 CDK5细胞的CDK5活性增加并通过CDK5抑制GTPase Rac1的活性才能表达Sa-beta-gal。 CDK5的PAD活性调节对于伴随衰老形态的肌动蛋白聚合响应PRB，激活的Ras或连续传递也是必要的。 CDK5的抑制会减弱sa-beta-gal的表达并阻断肌动蛋白聚合。我们进一步发现，衰老细胞中CDK5的一种底物是ERM蛋白Ezrin。活性PRB的表达诱导Ezrin的表达和定位改变，Ezrin是一种参与膜 - 细胞骨架信号传导的肌动蛋白结合蛋白。 PRB的表达导致刺激Ezrin的CDK5介导的Ezrin磷酸化，随后的膜缔合以及细胞形状变化的诱导，将PRB活性与衰老细胞的细胞骨架调节联系起来。这些结果开始阐明衰老的诱导和衰老形状变化的机制，并描述可能有助于衰老细胞影响肿瘤生长的能力的新途径。为了更清楚地了解CDK5和ERMS在衰老和肿瘤抑制中的作用，提出了三个特定的目的：1）确定CDK5在衰老细胞中的激活机理。 2）确定PRB如何激活Ezrin基因的转录，并使用此信息来了解衰老细胞中对PRB的转录反应。 3）确定构成型CDK5或ERM“敲低”或损失对增殖和肿瘤发生的影响。