Gupta S K, Gallego C, Lowndes J M, Pleiman C M, Sable C, Eisfelder B J, Johnson G L
Division of Basic Sciences, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
Mol Cell Biol. 1992 Jan;12(1):190-7. doi: 10.1128/mcb.12.1.190-197.1992.
Expression of GTPase-deficient Gi2 alpha subunit (alpha i2) mutant polypeptides and overexpression of the wild-type alpha i2 polypeptide in Rat 1a, Swiss 3T3, and NIH 3T3 fibroblasts altered normal growth regulation and induced a loss of contact inhibition. In Rat 1a cells (but not in NIH 3T3 or Swiss 3T3 cells), expression of the GTPase-deficient alpha i2 mutant polypeptides allowed colony formation in soft agar, which correlated with a loss in anchorage dependence and a decreased serum requirement. The altered growth regulatory properties of Rat 1a cells induced by expression of alpha i2 mutant polypeptides was not significantly inhibited by cotransfection with a dominant negative Ha-ras mutant polypeptide (Asn-17rasH), indicating that the activated Gi2 membrane signal transduction protein is uniquely capable of altering the regulation of Rat 1a cell growth by a predominantly c-ras-independent mechanism. The results show that GTPase-deficient alpha i2 mutant polypeptides have the properties of an oncogene that can induce the phenotypic characteristics of transformation in Rat 1a cells but that only a subset of these changes is observed with NIH 3T3 and Swiss 3T3 cells.
在大鼠1a、瑞士3T3和NIH 3T3成纤维细胞中，GTP酶缺陷型Gi2α亚基（αi2）突变多肽的表达以及野生型αi2多肽的过表达改变了正常的生长调节，并导致接触抑制丧失。在大鼠1a细胞中（但不在NIH 3T3或瑞士3T3细胞中），GTP酶缺陷型αi2突变多肽的表达使得细胞能够在软琼脂中形成集落，这与锚定依赖性丧失和血清需求降低相关。与显性负性Ha-ras突变多肽（Asn-17rasH）共转染并不能显著抑制由αi2突变多肽表达诱导的大鼠1a细胞生长调节特性的改变，这表明激活的Gi2膜信号转导蛋白能够通过主要不依赖c-ras的机制独特地改变大鼠1a细胞的生长调节。结果表明，GTP酶缺陷型αi2突变多肽具有癌基因的特性，能够在大鼠1a细胞中诱导转化的表型特征，但在NIH 3T3和瑞士3T3细胞中仅观察到这些变化的一个子集。
