PKCdelta and Salivary Gland Apoptosis

描述(申请人提供)：了解唾液腺细胞如何调节细胞凋亡对于开发保护唾液腺免受辐射损伤的疗法以及治疗干燥综合征、唾液肿瘤和其他细胞凋亡改变可能起作用的疾病至关重要。丝氨酸/苏氨酸蛋白激酶的信号转导在多种刺激诱导的细胞凋亡中起着至关重要的作用。我们之前已经证明，在活体中，腮腺中PKC4的缺失可以保护腮腺免受3-射线诱导的细胞凋亡。我的实验室的长期目标是了解蛋白激酶C(PKC)是如何调节细胞凋亡的，并利用这些信息来开发调节唾液腺细胞凋亡的治疗策略。我们以前已经证明了PKC4的核保留是诱导细胞凋亡的必要条件和充分条件，并在PKC4中发现了核进口所需的C末端核定位序列(NLS)。我们最近还发现了一个与NLS重叠的多聚脯氨酸结合位点(PxxP)，它调节PKC4的核靶向。在凋亡细胞中，PKC4的核滞留还需要在调节域的关键酪氨酸残基上进行磷酸化，这表明PKC4的磷酸化/去磷酸化起着促进细胞存活或死亡的开关作用。我们假设PKC4在酪氨酸上的磷酸化通过靶向细胞核来激活其促凋亡功能，并且PKC4的核保留在核输入和核输出的水平上都受到调节。我们目前的研究将集中在确定调控PKC4在凋亡细胞中核滞留的分子机制，目的是为分子治疗寻找合理的靶点。在这一应用中，我们将探索使用TAT-PKC4抑制肽在体内瞬时保护唾液腺免受辐射损伤。 公共卫生相关性：放射是头颈部癌症治疗中的关键组成部分，由于唾液腺靠近辐射部位，唾液腺的附带损害在这些患者中往往是不可避免的。每年约有40,000名新患者因头颈癌的放射治疗而患上唾液腺功能障碍，严重影响这些人的口腔健康和生活质量。慢性唾液腺功能下降被认为是由于对辐射敏感的细胞，特别是腮腺的浆液性腺泡细胞造成的不可逆转的细胞损伤所致。我们实验室和其他实验室最近的研究表明，唾液腺的辐射损伤通过激活细胞凋亡途径导致细胞死亡。我们的目标是了解唾液腺细胞凋亡是如何受到辐射的调节的。这些研究可能导致新的治疗策略的发展，以防止唾液腺损伤。

DESCRIPTION (provided by applicant): Understanding how apoptosis is regulated in salivary gland cells is critical for the development of therapeutics to protect salivary glands from irradiation induced damage and for the treatment of Sjogren's syndrome, salivary tumors and other diseases to which altered apoptosis may contribute. Signal transduction by serine/threonine protein kinases plays an essential role in apoptosis induced by a variety of stimuli. We have previously shown that loss of PKC4 in the parotid gland in vivo provides protection against 3-irradiation induced apoptosis. The long-term goal of my lab is to understand how protein kinase C (PKC) regulates apoptosis and to use this information to develop therapeutic strategies to modulate apoptosis in the salivary gland. We have previously shown the nuclear retention of PKC4 is necessary and sufficient to induce apoptosis, and have identified a C-terminal nuclear localization sequence (NLS) in PKC4 required for nuclear import. We have also recently discovered a polyproline binding site (PxxP) that overlaps with the NLS and that regulates nuclear targeting of PKC4. Nuclear retention of PKC4 in apoptotic cells also requires phosphorylation on key tyrosine residues in the regulatory domain, suggesting that phosphorylation/dephosphorylation of PKC4 functions as a switch to promote cell survival or cell death. We hypothesize that phosphorylation of PKC4 on tyrosine activates its pro-apoptotic function by targeting it to the nucleus, and that nuclear retention of PKC4 is regulated both at the level of both nuclear import and export. Our current studies will focus on identifying the molecular mechanisms that regulate nuclear retention of PKC4 in apoptotic cells, with the goal of identifying rational targets for molecular therapy. In this application we will explore the use of TAT-PKC4 inhibitory peptides to transiently protect the salivary gland from irradiation induced damage in vivo. PUBLIC HEALTH RELEVANCE: Radiation is a key component in the treatment of head and neck cancer, and collateral damage to the salivary glands is often inevitable in these patients due to the proximity of these glands to the radiation site. Each year approximately 40,000 new patients suffer from salivary gland dysfunction as a result of radiation therapy for head and neck cancer, significantly impacting the oral health and quality of life of these individuals. Chronic diminished salivary gland function is thought to result from irreversible cell damage to radiation sensitive cells, particularly the serous acinar cells of the parotid. Recent studies from our lab and others indicate that radiation damage to the salivary glands results in cell death via activation of apoptotic pathways. Our goal is to understand how salivary gland apoptosis is regulated in response to irradiation. These studies may lead to the development of novel therapeutic strategies to protect against salivary gland damage.