Cell cycle regulation in acinar cell death

化疗方案或头颈部照射后的唾液腺功能减退是一个主要的口腔健康问题。在这些条件下唾液腺腺泡细胞的损失似乎是通过细胞凋亡，这是一个基因编程的，需要能量的多步骤过程。凋亡刺激介导细胞死亡的机制之一是通过改变细胞周期调节。细胞死亡是对多种刺激的反应，包括生长因子退出、“死亡”受体的激活或DNA损伤，可能伴随着细胞周期蛋白依赖激酶（cdks）的异位激活，这可能导致不同类型的细胞（包括分泌性上皮细胞）不适当的细胞周期重新进入或进展。细胞周期蛋白依赖性激酶抑制剂（CKIs）的过度表达，抑制cdks和细胞周期进程的蛋白质，可以保护细胞免受与不同应激相关的凋亡。我们的假设是细胞周期蛋白依赖性激酶的不适当激活是腺泡细胞凋亡途径的一个组成部分，细胞周期蛋白依赖性激酶抑制剂可以通过调节cdk活性来减轻细胞凋亡。我们的初步数据表明，DNA增加了永生化和原代腺泡细胞中特定周期蛋白/cdk复合物的激酶活性。cdks的“异位”激活是腺泡细胞死亡的早期事件，与caspase-3激活同时发生。细胞周期蛋白/cdk激酶活性的增加也与CKI p27/kip1的表达缺失相关。在这个提议中，我们将研究DNA损伤诱导的cdk激活在动物细胞凋亡中的作用。我们将确定在腺泡细胞原代培养中，“异位”cdk激活是否先于或需要caspase- 3激活。我们将解决cdk激活是否对腺泡细胞死亡是必要的，我们将确定cdks是否磷酸化正常细胞周期底物或可能在细胞凋亡过程中作用于新的底物。我们将探讨CKIs/p27/kip1和p21/cip1通过cdk活性调节dna损伤诱导的细胞凋亡的能力。此外，我们将验证p21/cip1或p27/kip1在CKI零细胞中的保护功能。在许多类型的细胞中，肿瘤抑制因子53的激活通过诱导p21/cip1基因转录介导DNA损伤诱导的细胞凋亡。因此，我们将通过检测p53缺失细胞中DNA损伤和CKI表达的影响来研究肿瘤抑制因子在腺泡细胞死亡中的作用。

Salivary gland hypofunction following chemotherapeutic regimens or head/neck irradiation presents a major oral health problem. Loss of salivary gland acinar cells under these conditions appears to be through apoptosis, a genetically programmed, energy requiring multi-step process. One of the mechanisms through which apoptotic stimuli might mediate cell death is through altered cell cycle regulation. Cell death in response to diverse stimuli including growth factor withdrawal, activation of 'death' receptors or DNA damage may be accompanied by ectopic activation of cyclin dependent kinases (cdks) which may lead to inappropriate cell cycle re-entry or progression in diverse types of cells, including secretory epithelial cells. Over-expression of cyclin dependent kinase inhibitors (CKIs), proteins that inhibit cdks and therefore cell cycleprogression, can protect cells from apoptosis associated with different stresses. It is our hypothesis that inappropriate activation of cyclin dependent kinases is an integral part of the apoptotic pathway in acinar cells, and that cyclin dependent kinase inhibitors can attenuate apoptosis through modulating cdk activity. Our preliminary data suggest that suggest that DNA increases the kinase activity of specific cyclin/cdk complexes in immortalized and in primary acinar cells. 'Ectopic' activation of cdks is an early event in acinar cell death, occurring at the same time as caspase-3 activation. Increased cyclin/cdk kinase activity also correlates with loss of expression of the CKI p27/kip1. In this proposal, we will examine the role of DNA damage-induced cdk activation in animal cell apoptosis. We will determine whether 'ectopic' cdk activation precedes or requires caspase--3 activation in primary cultures of acinar cells. We will resolve whether cdk activation is necessary for acinar cell death, and we will ascertain whether cdks phosphorylate normal cell cycle substrates or perhaps act on novel substrates during apoptosis. We will explore the ability of the CKIs/p27/kip1 and p21/cip1 to modulate DNA-damage induced apoptosis through cdk activity. In addition, we will verify the protective functions of either p21/cip1 or p27/kip1 in CKI null cells. Activation of the tumor suppressor 53 mediates DNA damage induced apoptosis through induction of p21/cip1 gene transcription in many types of cell. Therefore, we will examine the role of the tumor suppressor in acinar cell death by testing the effects of DNA damage and CKI expression in p53 null cells.