Chang C J, Sonenshein G E
Department of Biochemistry, Boston University School of Medicine, MA 02118.
Matrix. 1991 Aug;11(4):242-51. doi: 10.1016/s0934-8832(11)80231-3.
The relationship between type I and type III collagen gene expression and the growth state of cultured bovine vascular smooth muscle cells has been investigated. Growth was modulated by incubation of subconfluent cultures of smooth muscle cells in media containing concentrations of fetal calf serum ranging from 10% to 0.5%. As the serum concentration was lowered, the doubling time increased from 17 hours to 70 hours, and collagen mRNA levels increased as judged by Northern blot analysis. The levels of induction were 5- to 15-fold for alpha 1(I), 2- to 3-fold for alpha 2(I), and 4- to 7-fold for alpha 1(III). Metabolic cell labelling with precursor amino acids indicated that type I and type III procollagen synthesis was elevated approximately 2-fold as growth slowed. A similar 2-fold increase occurred upon translation of isolated RNAs in a rabbit reticulocyte cell-free system. Nuclear run-on analysis indicated that increased collagen transcription can account for part of the increase in mRNA levels following incubation in lowered fetal calf serum. To further examine the influence of proliferation on collagen gene expression, smooth muscle cells were cultured in isoleucine-free medium, which resulted in quiescence within 36 hours. Induction of collagen mRNA levels was observed within 24 hours of incubation in isoleucine-free medium. Thus, collagen gene expression increases as the growth of vascular smooth muscle cells is slowed by either deprivation of growth factors or essential amino acids. Regulation is mediated at several sites, including gene transcription and mRNA translation, and possibly post-transcriptional steps.
研究了I型和III型胶原蛋白基因表达与培养的牛血管平滑肌细胞生长状态之间的关系。通过在含有10%至0.5%不同浓度胎牛血清的培养基中培养亚汇合的平滑肌细胞培养物来调节生长。随着血清浓度降低，倍增时间从17小时增加到70小时，通过Northern印迹分析判断，胶原蛋白mRNA水平升高。α1(I)的诱导水平为5至15倍，α2(I)为2至3倍，α1(III)为4至7倍。用前体氨基酸进行代谢细胞标记表明，随着生长减缓，I型和III型前胶原合成增加约2倍。在兔网织红细胞无细胞系统中翻译分离的RNA时也出现了类似的2倍增加。核转录分析表明，在降低胎牛血清浓度的培养基中孵育后，胶原蛋白转录增加可部分解释mRNA水平的升高。为了进一步研究增殖对胶原蛋白基因表达的影响，将平滑肌细胞培养在无异亮氨酸的培养基中，这导致在36小时内细胞静止。在无异亮氨酸培养基中孵育24小时内观察到胶原蛋白mRNA水平的诱导。因此，当血管平滑肌细胞的生长因生长因子或必需氨基酸的剥夺而减缓时，胶原蛋白基因表达增加。调节作用在多个位点介导，包括基因转录、mRNA翻译以及可能的转录后步骤。
