James G L, Brown M S, Cobb M H, Goldstein J L
Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235.
J Biol Chem. 1994 Nov 4;269(44):27705-14.
A benzodiazepine peptidomimetic, BZA-5B, inhibits farnesylation of H-Ras and normalizes the morphology of Rat-1 cells transformed with H-RasV12 at concentrations that do not affect the growth of untransformed Rat-1 cells. In the current experiments, we show that BZA-5B decreases the active forms of enzymes in the mitogen-activated protein (MAP) kinase signaling cascade, including Raf, MAP kinase kinase (MEK), and MAP kinase, in cells transformed with H-RasV12. BZA-5B had no effect on these enzymes in cells transformed with H-RasV12,L189, which is geranylgeranylated rather than farnesylated. In cells transformed with H-RasV12, BZA-5B reduced the activities of enzymes in the MAP kinase pathway at concentrations that only partially blocked farnesylation of H-RasV12, suggesting that nonfarnesylated H-RasV12 is a dominant inhibitor of the action of farnesylated H-RasV12 in the BZA-5B treated cells. In untransformed Rat-1 cells, BZA-5B did not inhibit MAP kinase activity nor did it prevent the acute activation triggered by epidermal growth factor, even though farnesylated endogenous H-Ras was no longer detectable. These data raise the possibility that untransformed cells contain a form of Ras (K-Ras or N-Ras) whose prenylation is not inhibited by BZA-5B, thus allowing them to resist the effects of BZA-5B.
一种苯二氮䓬类肽模拟物BZA-5B，可抑制H-Ras的法尼基化，并使由H-RasV12转化的Rat-1细胞的形态正常化，其浓度不影响未转化的Rat-1细胞的生长。在当前实验中，我们发现BZA-5B可降低H-RasV12转化细胞中丝裂原活化蛋白（MAP）激酶信号级联反应中酶的活性形式，包括Raf、MAP激酶激酶（MEK）和MAP激酶。BZA-5B对由H-RasV12、L189转化的细胞中的这些酶没有影响，H-RasV12、L189是香叶基香叶基化而非法尼基化的。在H-RasV12转化的细胞中，BZA-5B在仅部分阻断H-RasV12法尼基化的浓度下降低了MAP激酶途径中酶的活性，这表明未法尼基化的H-RasV12是BZA-5B处理细胞中法尼基化的H-RasV12作用的主要抑制剂。在未转化的Rat-1细胞中，BZA-5B既不抑制MAP激酶活性，也不阻止表皮生长因子触发的急性激活，即使法尼基化的内源性H-Ras不再可检测到。这些数据增加了一种可能性，即未转化的细胞含有一种Ras形式（K-Ras或N-Ras），其异戊二烯化不受BZA-5B抑制，从而使它们能够抵抗BZA-5B的作用。
