Dissociation of mitogenesis and transforming activity by C-terminal truncation of the insulin-like growth factor-I receptor.
Dissociation of mitogenesis and transforming activity by C-terminal truncation of the insulin-like growth factor-I receptor.
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通过胰岛素样生长因子-I 受体 C 端截短来解离有丝分裂和转化活性。
DOI：
10.1006/excr.1995.1168
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Baserga,R
中科院分区：
文献类型：
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作者：
Surmacz,E;Sell,C;Swantek,J;Kato,H;RobertsJr,CT;LeRoith,D;Baserga,R
我们研究了R细胞中具有108个氨基酸c端截断的IGF-I受体的有丝分裂和转化能力，R细胞是来源于小鼠胚胎的3t3样细胞，其中IGF-I受体基因被靶向同源重组破坏。R细胞稳定地转染了编码野生型或截断的人IGF-I受体的表达质粒，能够在仅添加IGF-I的无血清培养基中生长。这种反应是在广泛的受体水平上观察到的。过表达野生型IGF-I受体的R细胞也在软琼脂中形成集落，并且通过SV40大T抗原的共表达增强了集落的形成。然而，所有被检测的表达截断的igf - 1受体的r细胞克隆，即使在T抗原存在的情况下，在软琼脂中的生长能力也明显受损。在软琼脂中不能形成集落并不是因为信号转导的定量损伤，因为(1)sv40转化的细胞具有生理水平的野生型IGF-I受体，但对IGF-I没有细胞增殖反应，而是在软琼脂中生长；(2)同时转染截断受体和T抗原的r细胞对IGF-I有丝分裂反应，但在软琼脂中不能形成菌落；(3)一些受体被截断的克隆的受体表达水平约为野生型细胞的100倍；(4)被截断受体稳定转染的细胞中，IGF-I受体信号转导的几个参数没有受损。此外，在IGF-IR截断的细胞中过度表达激活的ras并不能恢复它们在不依赖锚定条件下的增殖能力。我们得出结论，IGF-I受体的最后108个氨基酸对于IGF-I的有丝分裂反应不是必需的，但对于转化是必需的（通过在软琼脂中生长的能力来评估），这表明这两个功能可以在分子内分离。此外，尽管ras（激活）在转化过程中确实发挥了作用，但IGF-IR的转化活性也需要ras独立的信号元件。
We have investigated the mitogenic and transforming ability of an IGF-I receptor with a 108-amino-acid C-terminal truncation in R cells, which are 3T3-like cells derived from mouse embryos in which the IGF-I receptor genes have been disrupted by targeted homologous recombination. R cells stably transfected with expression plasmids encoding either a wild-type or a truncated human IGF-I receptor were capable growing in serum-free medium supplemented solely with IGF-I. This response was observed over a wide range of receptor levels. R cells overexpressing the wild-type IGF-I receptor also formed colonies in soft agar, and colony formation was augmented by coexpression of the SV40 large T antigen. However, all the examined clones of R-cells expressing the truncated IGF-I receptor exhibited a dramatically impaired ability to grow in soft agar, even in the presence of the T antigen. The inability to Form colonies in soft agar was not due to a quantitative impairment of signal transduction, because: (1) SV40-transformed cells with a physiological level of the wild-type IGF-I receptor did not respond to IGF-I with cell proliferation, but grew in soft agar; (2) R-cells stably transfected with both a truncated receptor and T antigen, on the contrary, responded with mitogenesis to IGF-I but could not form colonies in soft agar; (3) some clones with the truncated receptor expressed levels of receptor roughly 100-fold the level of wild-type cells; and (4) several parameters of IGF-I receptor signal transduction were not impaired in cells stably transfected with a truncated receptor. Furthermore, overexpression of an activated ras in cells with the truncated IGF-IR did not restore their ability to proliferate under anchorage-independent conditions. We conclude that the last 108 amino acids of tile IGF-I receptor are not essential for a mitogenic response to IGF-I, but are required for transformation (as assessed by the ability to grow in soft agar), indicating that these two functions can be dissociated at an intramolecular level. Moreover, although ras (activated) certainly plays a role in transformation, the transforming activity of the IGF-IR also requires signaling elements that are ras-independent.