Sphingosine Kinases in Cancer Cell Signaling

描述(由申请人提供)：鞘氨酸激酶(SphK)是一种调节鞘氨醇-1-磷酸(S1P)水平的中心酶，S1P是一种具有生物活性的鞘氨醇代谢产物，也是一个5个S1P受体家族的配体。我们之前已经克隆并鉴定了两种不同的亚型，SphK1和SphK2。SphK1被多种刺激激活，促进细胞增殖、细胞存活、迁移和肿瘤形成。SphK1和细胞内产生的S1P可以发出信号由内向外调节细胞骨架重排和细胞运动，但不依赖S1P受体刺激细胞生长和抑制细胞凋亡。值得注意的是，尽管SphK2在序列上与SphK1高度相似，并且具有相同的5个保守结构域，但我们最近发现，SphK2不仅没有促进生长和存活，反而抑制了生长，也促进了细胞凋亡。这项提案的目的是确定这两种密切相关、相似的同工酶如何产生相同的产品，但却具有如此不同的功能。我们将检验这一假说，即SphK1和SphK2的相反作用是由于它们特定的调节和/或转位到不同的细胞间隔，以产生不同的S1P池或具有独特功能的其他磷酸化的狮身人面像碱基，从而影响对转化的表型特别重要的细胞过程。将利用生化和遗传学方法来确定内源性SphK1和SphK2在癌细胞的生长、存活和运动中是否具有多余、重叠、互补或拮抗的功能。我们还将阐明它们在调节神经酰胺生物合成和鞘磷脂体中未知的作用，并确定SphK2是否是一个连接BH3-2家族、钙稳态和细胞凋亡调节的双功能蛋白。总的来说，这些研究将为SphK1和SphK2的生理作用增加一个新的维度，它们的活动在控制S1P水平方面是核心和必需的，S1P是一种强大的脂质介质，调节着许多对癌症至关重要的细胞过程。

DESCRIPTION (provided by applicant): Sphingosine kinase (SphK) is a central enzyme regulating the levels of sphingosine-1-phosphate (S1P), a bioactive sphingolipid metabolite and a ligand for a family of 5 S1P receptors. We have previously cloned and characterized 2 distinct isoforms, SphK1 and SphK2. SphK1 is activated by a numerous stimuli to promote cell proliferation, cell survival, migration and tumor formation. SphK1 and intracellularly generated S1P can signal "inside-out" to regulate cytoskeletal rearrangements and cell movement, yet stimulates cell growth and suppresses apoptosis independently of S1P receptors. Remarkably, although highly similar in sequence to SphK1 and possessing the same 5 conserved domains, we recently found that SphK2 rather than promoting growth and survival, suppressed growth and also enhanced apoptosis. The goal of this proposal is to determine how these 2 very closely related and similar isoenzymes that can produce the same product can have such different functions. We will examine the hypothesis that the opposite actions of SphK1 and SphK2 result from their specific regulation and/or translocation to distinct cellular compartments to produce distinct pools of S1P or other phosphorylated sphingoid bases that have unique functions, and thus affect cellular processes that are particularly important for the transformed phenotype. Biochemical and genetic approaches will be utilized to determine whether endogenous SphK1 and SphK2 have redundant, overlapping, complementary, or antagonistic functions in growth, survival and motility of cancer cells. We will also elucidate their unrecognized roles in regulating ceramide biosynthesis and the sphingolipidome and determine whether SphK2 is a dual function BH3-only protein that links the Bcl-2 family, calcium homeostasis, and regulation of apoptosis. Collectively, these studies will add a new dimension to the physiological roles of SphK1 and SphK2 whose activities are central and obligatory in controlling levels of S1P, a potent lipid mediator that regulates many cellular processes important for cancer.