Sphingolipid Metabolism and Signaling in the Regulation of Senescence and Aging

摘要 脂代谢和信号转导在衰老和长寿的调节中起着关键作用。生物活性 鞘磷脂神经酰胺可诱导衰老，抑制神经酰胺合成可延长寿命 跨度。抗增殖神经酰胺的下游靶点之一是端粒酶，端粒酶在转录水平上 神经酰胺使其失声，导致多种哺乳动物细胞衰老。神经酰胺可以代谢成 通过鞘氨醇激酶1或2(SphK1或SphK2)产生支持生存的鞘氨醇1-磷酸(S1P)。而当 SphK1产生的S1P在血浆G蛋白偶联受体(GPCR)信号转导中起重要作用 膜，SphK2/S1P主要定位于核膜。我们的初步数据显示SphK2- 产生的S1P结合端粒酶逆转录酶(TERT)蛋白，稳定端粒酶，保护各种 人类和小鼠的细胞类型，包括成纤维细胞和肺上皮细胞，由于端粒损伤和 随后延缓衰老。反过来，药物抑制或SphK2的基因缺失，但不是 SphK1导致TERT的快速泛素化/降解，加速端粒损伤，并诱导 SphK2-/-小鼠体内培养成纤维细胞和睾丸或皮肤组织的衰老。然而，SphK2是如何- 产生的S1P结合并控制TERT的稳定性，以及抑制SphK2/S1P代谢如何导致 端粒酶不稳定和端粒损伤诱导衰老加速衰老 信令仍然未知，这将在此应用程序中得到回答。因此，此应用程序旨在测试 核膜SphK2/S1P鞘磷脂信号调节衰老和衰老的新假说 通过控制端粒酶和端粒损伤来衰老。这一假设将在以下具体情况下得到检验 目的：1)确定SphK2产生的S1P调节端粒酶稳定性和 衰老。目的2)明确抑制SphK2/S1P-hTERT复合体引起的端粒损伤 调节衰老。目的3)确定诱导SphK2/S1P代谢和信号转导如何阻止端粒 损伤导致的衰老和衰老。由于我们在鞘脂信号方面的强大专业知识，我们是理想的 定位于开发基于机制的干预措施来控制端粒酶/端粒损伤/衰老和 延长寿命和/或健康时间，这对癌症等与衰老有关的疾病有重要影响 和阿尔茨海默病(AD)。

SUMMARY Lipid metabolism and signaling play key roles in the regulation of senescence and longevity. The bioactive sphingolipid ceramide induces senescence, and that inhibition of ceramide synthesis results in increased life span. One of the down-stream targets of anti-proliferative ceramide is telomerase, which is transcriptionally silenced by ceramide, resulting in senescence in various mammalian cells. Ceramide can be metabolized to generate pro-survival sphingosine 1-phosphate (S1P) by sphingosine kinases 1 or 2 (SphK1 or SphK2). While SphK1-generated S1P plays important roles in G protein coupled receptor (GPCR) signaling in the plasma membrane, SphK2/S1P is localized mainly to nuclear membrane. Our preliminary data suggest that SphK2- generated S1P binds telomerase reverse transcriptase (TERT) protein, stabilizing telomerase, protecting various human and murine cell types, including fibroblasts and lung epithelial cells, from telomere damage and subsequently delaying senescence. Reciprocally, pharmacologic inhibition or genetic deletion of SphK2, but not SphK1, results in rapid TERT ubiquitination/degradation, accelerating telomere damage, and inducing senescence in fibroblasts in culture and in testes or skin tissues of SphK2-/- mice in vivo. However, how SphK2- generated S1P binds and controls TERT stability, and how inhibition of SphK2/S1P metabolism results in accelerated aging through induction of senescence in response to telomerase instability and telomere damage signaling remain unknown, which will be answered in this application. Thus, this application is designed to test a novel hypothesis that sphingolipid signaling by SphK2/S1P in nuclear membranes regulate senescence and aging by controlling telomerase and telomere damage. This hypothesis will be tested in the following Specific Aims: Aim 1) Determine the mechanism whereby SphK2-generated S1P regulates telomerase stability and senescence. Aim 2) Define how telomere damage induced by inhibition of the SphK2/S1P-hTERT complex mediates senescence. Aim 3) Identify how inducing SphK2/S1P metabolism and signaling prevents telomere damage-induced senescence and aging. Because of our strong expertise in sphingolipid signaling, we are ideally positioned to develop mechanism-based interventions to control telomerase/telomere-damage/senescence and increase life and/or health span, which have important implications in aging-associated diseases such as cancer and Alzheimer’s disease (AD).