Krupsky M, Kuang P P, Goldstein R H
Pulmonary Center and the Department of Biochemistry, Boston University School of Medicine and the Boston Veterans Affairs Medical Center, Boston, Massachusetts 02118, USA.
J Biol Chem. 1997 May 23;272(21):13864-8. doi: 10.1074/jbc.272.21.13864.
The steady state levels of alpha1(I) collagen mRNA are decreased by retinoic acid and prostaglandin E2. These effector substances decrease the uptake of A system amino acids. We examined the effect of amino acid deprivation on the steady state levels of alpha1(I) collagen in human lung fibroblasts. Maintenance of fibroblasts in amino acid-free medium decreased alpha1(I) collagen mRNA levels by 29% at 24 h and 78% at 72 h. Frequent refeeding of cultures with amino acid-free medium resulted in more rapid decreases in intracellular amino acids and in alpha1(I) collagen mRNA levels. The decrease in alpha1(I) collagen mRNA levels was mediated by decreases in mRNA stability as assessed by a half-life determination using actinomycin D and by decreases in the rate of transcription as assessed by nuclear run-on assay. Treatment of fibroblasts with medium containing amino acids resulted in rapid restoration of alpha1(I) collagen mRNA levels. This increase in alpha1(I) collagen mRNA expression required protein synthesis as determined by cycloheximide sensitivity and was inhibited by prostaglandin E2. These data indicate that alpha1(I) collagen mRNA levels are sensitive to alterations in the amount of intracellular amino acids and suggest a potential mechanism whereby alpha1(I) collagen accumulation may be regulated independent of inflammatory mediators following lung injury.
视黄酸和前列腺素E2可降低α1（I）型胶原mRNA的稳态水平。这些效应物质会减少A系统氨基酸的摄取。我们研究了氨基酸剥夺对人肺成纤维细胞中α1（I）型胶原稳态水平的影响。将成纤维细胞置于无氨基酸培养基中培养，24小时时α1（I）型胶原mRNA水平下降29%，72小时时下降78%。频繁用无氨基酸培养基对培养物进行再喂养，导致细胞内氨基酸和α1（I）型胶原mRNA水平下降得更快。通过放线菌素D半衰期测定评估，α1（I）型胶原mRNA水平的下降是由mRNA稳定性降低介导的；通过核转录分析评估，是由转录速率降低介导的。用含氨基酸的培养基处理成纤维细胞，可使α1（I）型胶原mRNA水平迅速恢复。α1（I）型胶原mRNA表达的这种增加需要蛋白质合成，这是通过环己酰亚胺敏感性测定确定的，并且受到前列腺素E2的抑制。这些数据表明，α1（I）型胶原mRNA水平对细胞内氨基酸量的变化敏感，并提示了一种潜在机制，通过该机制，肺损伤后α1（I）型胶原的积累可能独立于炎症介质进行调节。
