SPHINGOSINE DEPENDENT KINASE AND CARCINOGENESIS

我们发现了一类由鞘氨醇（Sph）或N，N-二甲基鞘氨醇（DMS）激活，但不被Cer， Sph-1- p或其他鞘脂或磷脂激活的蛋白激酶，并将其称为“鞘氨醇依赖性蛋白激酶”（SDKs）。一种SDK，称为SDK1，专门磷酸化某些14-3-3蛋白（eta, beta, zeta），但不磷酸化其他（sigma, tau）。另一种SDK （SDK2）磷酸化钙网蛋白和蛋白二硫异构酶。第三个SDK （SDK3）磷酸化热休克蛋白和葡萄糖调节蛋白。因此，迄今为止检测到的所有sdk的底物都是控制稳态和信号转导的适配器/分子伴侣。我们还发现Sph和DMS抑制bcl-2基因表达，激活酪氨酸磷酸酶MKP-1抑制MAPK，从而抑制细胞生长和诱导凋亡。在此基础上，我们拟开展以下研究：(1)SDK1、SDK2、SDK3及其基因的鉴定和克隆，为进一步了解Sph和DMS在维持体内平衡和信号转导中的功能作用提供基础。(2) Sph和DMS抑制细胞生长和诱导细胞凋亡的作用机制，特别关注它们(1)激活MKP-1，(2)抑制bcl-2癌基因表达。我们的初步研究还表明，口服DMS或其水溶性衍生物N，N，N-三甲基- sph （TMS）可抑制甲基氧乙酸甲醇诱导的CF1小鼠肠道和结直肠癌的发展。我们将对日粮中添加DMS和TMS的效果进行系统研究。在确定抑制作用后，将研究其与SDKs、MAPK、bcl-2等信号转导活性的关系。

A class of protein kinases activated by sphingosine (Sph) or N,N- dimethylsphingosine (DMS), but not by Cer, Sph-1-P, or other sphingolipids or phospholipids, was found by us and termed "sphingosine-dependent protein kinases" (SDKs). One SDK, termed SDK1, specifically phosphorylates certain isoforms 14-3-3 protein ( eta ,beta, zeta) but not others (sigma, tau). Another SDK (SDK2) phosphorylates calreticulin and protein disulfide isomerase. A third SDK (SDK3) phosphorylates heat shock protein and glucose regulated protein. Thus, substrates of all SDKs so far detected are adapters/molecular chaperones controlling homeostasis and signal transduction. We also found that Sph and DMS inhibit bcl-2 gene expression, and activate tyrosine phosphatase MKP-1 to inhibit MAPK, with consequent inhibition of cell growth and induction of apoptosis. Based on these preliminary findings, we propose to study: (1) Characterization and cloning of SDK1, SDK2, SDK3, and their genes, which will facilitate our understanding of the functional role of Sph and DMS in maintaining homeostasis and signal transduction. (2) Mechanisms of the growth-inhibitory and apoptosis-inducing effects of Sph and DMS, with special focus on their (i) activation of MKP-1, and (ii) inhibition of bcl-2 oncogene expression. Our preliminary studies also indicate that oral administration of DMS or its water-soluble derivative N,N,N-trimethyl-Sph (TMS) inhibits intestinal and colorectal cancer development in CF1 mice induced by methylazoxymethanol acetate. We will perform systematic studies on the effect of DMS and TMS added to diet. In the inhibitory effect is confirmed, its mechanism will be studied in relation to activities of SDKs, MAPK, bcl-2, and other signal transducers.