FARNESOL MODIFICATION OF KIRSTEN-RAS EXON 4B-PROTEIN IS ESSENTIAL FOR TRANSFORMATION
FARNESOL MODIFICATION OF KIRSTEN-RAS EXON 4B-PROTEIN IS ESSENTIAL FOR TRANSFORMATION
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DOI：
10.1073/pnas.87.8.3042
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发表时间：
1990-04-01
影响因子：
11.1
通讯作者：
DER, CJ
中科院分区：
文献类型：
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作者：
JACKSON, JH;COCHRANE, CG;DER, CJ
ras 蛋白的致癌形式在细胞质中合成，并且必须与膜结合才能引起恶性转化。胆固醇生物合成中的棕榈酸和类异戊二烯（金合欢醇）中间体附着在 H-ras、N-ras 和 Kirsten-ras (K-ras) 外显子 4A 编码蛋白 C 末端附近的单独半胱氨酸残基上。这些脂质修饰被认为可以促进或稳定 ras 蛋白与膜的结合。由于防止异戊二烯化也可防止棕榈酰化，因此不可能单独检查异戊二烯化的重要性。然而，致癌的人类 [Val12]K-ras 4B 蛋白不是帕利托酰化的，而是异戊二烯基化的、膜相关的和完全转化的。因此，我们构建了未异戊二烯化的突变体 [Val12]K-ras 4B 蛋白，以检查在没有棕榈酰化的情况下异戊二烯化的影响。非异戊二烯化突变蛋白均未能与细胞膜结合，也无法转化 NIH 3T3 细胞。此外，用康克汀药物抑制类异戊二烯和胆固醇合成也会降低 [Val12]K-ras 4B 蛋白异戊二烯化和膜结合。这些结果明确证明异戊二烯化而不是棕榈酰化对于 ras 膜结合和 ras 转化活性至关重要。这些发现清楚地表明了金合欢醇修饰 ras 蛋白的生物学意义，并表明这种修饰对于促进其他异戊二烯化蛋白的加工、运输和生物活性可能很重要。由于 K-ras 是多种人类恶性肿瘤中最常被激活的癌基因，因此对该通路的研究可能会带来重要的治疗方法。
Oncogenic forms of ras proteins are synthesized in the cytosol and must become membrane associated to cause malignant transformation. Palmitic acid and an isoprenoid (farnesol) intermediate in cholesterol biosynthesis are attached to separate cysteine residues near the C termini of H-ras, N-ras, and Kirsten-ras (K-ras) exon 4A-encoded proteins. These lipid modifications have been suggested to promote or stabilize the association of ras proteins with membranes. Because preventing isoprenylation also prevents palmitoylation, examining the importance of isoprenylation alone has not been possible. However, the oncogenic human [Val12]K-ras 4B protein is not palitoylated but is isoprenylated, membrane associated, and fully transforming. We therefore constructed mutant [Val12]K-ras 4B proteins that were not isoprenylated to examine the effects of isoprenylation in the absence of palmitoylation. The nonisoprenylated mutant proteins both failed to associate with membranes and did not transform NIH 3T3 cells. In addition, inhibition of isoprenoid and cholesterol synthesis with the drug compactin also decreased [Val12]K-ras 4B protein isoprenylation and membrane association. These results unequivocally demonstrate that isoprenylation, rather than palmitoylation, is essential for ras membrane binding and ras transforming activity. These findings clearly indicate the biological significance of ras protein modification by farnesol and suggest that this modification may be important for facilitating the processing, trafficking, and biological activity of other isoprenylated proteins. Because K-ras is the most frequently activated oncogene in a wide spectrum of human malignancies, study of this pathway could lead to important therapeutic treatments.