MARCKS functions as a novel growth suppressor in cells of melanocyte origin
MARCKS functions as a novel growth suppressor in cells of melanocyte origin
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DOI：
10.1093/carcin/17.4.683
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发表时间：
1996-04-01
期刊：
影响因子：
4.7
通讯作者：
Goss, MW
中科院分区：
文献类型：
--
作者：
Brooks, G;Brooks, SF;Goss, MW
蛋白激酶C（PKC）在调节培养的黑素细胞的生长中起关键作用。我们先前已经表明，PKC的主要生理底物，80 kDa肉豆蔻酰化富含丙氨酸的C-激酶底物（MARCKS），可以在短暂暴露于生物活性佛波酯的静止的、非致瘤性黑素细胞中磷酸化，但不能在佛波酯处理的黑素细胞中磷酸化，同基因恶性黑色素瘤细胞，尽管其普遍存在的分布，MARCKS在细胞生长和转化中的功能仍有待明确证明。我们在此报道，与同基因正常Mel-ab黑色素细胞相比，MARCKS mRNA和蛋白水平在自发衍生的小鼠B16黑色素瘤细胞系中显著下调。相反，致瘤性v-Ha-ras转化的黑素细胞系LTR Pas 2显示出高的MARCKS磷酸化基础水平，其不被用佛波醇酯处理的细胞所增强。此外，LTR Pas 2细胞中MARCKS的蛋白水平与Mel-ah黑素细胞中表达的那些相似。然而，在所研究的6个鼠肿瘤细胞系中的4个中，MARCKS蛋白的水平几乎检测不到，用含有MARCKS cDNA的质粒以有义方向转染B16细胞产生了两个新霉素抗性克隆，与对照细胞相比，它们显示出降低的增殖能力和降低的非贴壁依赖性生长。相反，用反义MARCKS构建体转染产生了许多集落，与对照细胞相比，这些集落显示出增强的生长和转化潜力，因此，MARCKS似乎在黑素细胞起源的细胞的自发转化中充当一种新的生长抑制剂，并且可能在其他癌症的肿瘤进展中发挥更普遍的作用。
Protein kinase C (PKC) plays a pivotal role in modulating the growth of melanocytic cells in culture, We have shown previously that a major physiological substrate of PKC, the 80 kDa myristoylated alanine-rich C-kinase substrate (MARCKS), can be phosphorylated in quiescent, non-tumorigenic melanocytes exposed transiently to a biologically active phorbol ester, but cannot be phosphorylated in phorbol ester-treated, syngeneic malignant melanoma cells, Despite its ubiquitous distribution, the function of MARCKS in cell growth and transformation remains to be demonstrated clearly, We report here that MARCKS mRNA and protein levels are down-regulated significantly in the spontaneously derived murine B16 melanoma cell line compared with syngeneic normal Mel-ab melanocytes, In contrast, the tumourigenic v-Ha-ras-transformed melanocytic line, LTR Pas 2, showed a high basal level of MARCKS phosphorylation which was not enhanced by treatment of cells with phorbol ester, Furthermore, protein levels of MARCKS in LTR Pas 2 cells were similar to those expressed in Mel-ah melanocytes, However, in four out of six murine tumour cell lines investigated, levels of MARCKS protein were barely detectable, Transfection of B16 cells with a plasmid containing the MARCKS cDNA in the sense orientation produced two neomycin-resistant clones displaying reduced proliferative capacity and decreased anchorage-independent growth compared with control cells, In contrast, transfection with the antisense MARCKS construct produced many colonies which displayed enhanced growth and transforming potential compared with control cells, Thus, MARCKS appears to act as a novel growth suppressor in the spontaneous transformation of cells of melanocyte origin and may play a more general role in the tumour progression of other carcinomas.