Experimental pathologic study on the pathogenesis of cerebral lesions in tuberous sclerosis

结节性硬化症是由TSC1或TSC2基因突变引起的。TSC2基因的蛋白产物Tuberin是胰岛素信号转导途径的负调节因子。Tuberin上游的因子包括胰岛素、PI3K和Akt，tuberin下游的因子包括Rheb、mTOR、p70S6K和S6。先前的研究表明，在人类TSC病变(肿瘤和缰裂)中，Tuberin的功能障碍导致mTOR途径的过度激活和S6的过度磷酸化。根据两次命中假说，肿瘤会发生。PI3K和Akt等向上因子的活性被认为受到反馈机制的抑制。在这项研究中，我们首先通过对Eker大鼠的免疫组织化学研究来检验这些假说，Eker大鼠是一种由功能缺失的突变…引起的TSC动物模型关于TSC2基因的更多信息。Eker大鼠大脑和肾脏恶性肿瘤未见Akt过度激活。在一小部分肿瘤细胞中发现mTOR和p70S6K的过度磷酸化。与反应性星形胶质细胞中Akt和p70S6K的过度磷酸化相反，在大脑缰核(皮质结节)，Akt的磷酸化正常，而mTOR和p70S6K的磷酸化缺失。所有这些病变，包括肿瘤和触须，都显示出显著的S6过度磷酸化。我们用Western blotting检测了这些因子的磷酸化状态。在肾脏(非癌组织)和大脑中，Akt、Tuberin、mTOR、p70S6K和S6的表达和磷酸化均正常。在Eker大鼠肾细胞癌模型中，Akt低磷酸化，tuberin低表达，mTOR高表达，S6高磷酸化，而p70S6K无高磷酸化。这些结果提示，该通路的下游到上游存在负反馈机制，S6被p70S6K以外的其他因素激活。较少

Tuberous sclerosis complex (TSC) is caused by a mutation of either the TSC1 or TSC2 gene. The protein product of the TSC2 gene, tuberin, is a negative regulator of the insulin signal transduction pathway. Factors upstream of tuberin include insulin, PI3K and Akt, and those downstream of tuberin include Rheb, mTOR, p70S6K and S6. Previous studies have revealed that, in human TSC lesions (tumors and hamartias) dysfunction of tuberin causes hyper-activation of the mTOR pathway and over-phosphorylation of S6. Tumors occur according to the two-hit hypothesis. The activity of upward factors, such as PI3K and Akt, was hypothesized to be suppressed by a feedback mechanism. In hamartias like cortical tubers of the cerebral cortex, there is no second hit, and the possibility of constitutive activation of the PI3K/Akt pathway has been pointed out.In this study, we first examined these hypotheses by immunohistochemical studies of Eker rat, an animal model of TSC caused by a loss-of-function mutati … More on of the Tsc2 gene. Malignant tumors of the Eker rat cerebrum and kidneys showed no hyper-activation of Akt. The hyper-phosphorylation of mTOR and p70S6K was noted in a small subpopulation of tumor cells. In the cerebral hamartia (cortical tuber), there was normal Akt phosphorylation, as well as an absence of mTOR and p70S6K phosphorlation, in contrast to hyper-phosphorylation of Akt and p70S6K in reactive astrocytes. All these lesions, both tumors and hamartias, showed prominent hyper-phosphorylation of S6.We nest examined the phophorylation status of these factors by Western blotting. In the kidneys (non-cancerous tissues) and cerebrum, the expression and phosphorylation of Akt, tuberin, mTOR, p70S6K and S6 was normal. The renal cell cancer of Eker rats showed hypo-phosphorylation of Akt, low expression of tuberin, high expression of mTOR and hyper-phosphorylation of S6, but no hyper-phosphorylation of p70S6K.These results suggested a negative feedback mechanism from the downstream to the upstream of this pathway, and S6 activation by a factor other than p70S6K. Less