PKCdelta and Salivary Gland Apoptosis

描述（由申请人提供）：了解唾液腺细胞的凋亡是如何调节的，这对于开发治疗方法来保护唾液腺免受辐射引起的损伤，以及治疗干燥综合征、唾液腺肿瘤和其他可能导致细胞凋亡改变的疾病至关重要。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重要作用。我们之前已经证明，体内腮腺中PKC4的缺失可以防止3-辐照诱导的细胞凋亡。我实验室的长期目标是了解蛋白激酶C （PKC）如何调节细胞凋亡，并利用这些信息制定治疗策略来调节唾液腺的细胞凋亡。我们之前已经证明PKC4的核保留是诱导细胞凋亡的必要和充分条件，并在PKC4中发现了核导入所需的c端核定位序列（NLS）。我们最近还发现了一个与NLS重叠的聚脯氨酸结合位点（PxxP），它调节PKC4的核靶向。凋亡细胞中PKC4的核保留也需要在调节区域的关键酪氨酸残基上磷酸化，这表明PKC4的磷酸化/去磷酸化作为促进细胞存活或细胞死亡的开关。我们假设PKC4在酪氨酸上的磷酸化通过将其靶向细胞核激活其促凋亡功能，PKC4的核保留在核输入和核输出水平上都受到调节。我们目前的研究将集中在确定凋亡细胞中PKC4核保留的分子机制，以确定分子治疗的合理靶点。在这个应用中，我们将探索使用TAT-PKC4抑制肽在体内暂时保护唾液腺免受辐照引起的损伤。

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.