Bussolati O, Uggeri J, Rotoli B M, Franchi-Gazzola R, Gazzola G C
Istituto di Patologia Generale, Università di Parma, Italy.
Biochim Biophys Acta. 1993 Sep 19;1151(2):153-60. doi: 10.1016/0005-2736(93)90099-l.
The relationship between the transport of anionic amino acids and the proliferative status of the cell population has been studied in NIH-3T3 cells. Proliferative quiescence, verified by determinations of growth-rate quotient and incorporation of thymidine, is associated with a marked increase of the influx of L-aspartate. After 7-10 days of serum starvation, the initial influx of L-aspartate increases by 8-10-times with respect to the transport activity determined in growing cells. The operational properties of the influx of L-aspartate are similar in growing and quiescent cells; in particular, the influx of the anionic amino acid is mostly Na(+)-dependent and completely suppressed by an excess of L-glutamate and D-aspartate, but not of D-glutamate. These features suggest that, in both cases, aspartate uptake occurs through system X(-)AG. The quiescence-related increase in aspartate transport is gradual, sensitive to the inhibition of protein synthesis and referable to the enhanced maximal capacity of transport system X(-)AG. Restoration of serum concentration in the culture medium of serum-starved cells causes a decrease in aspartate transport that is maximal in correspondence to late G1/S phases. It is concluded that the X(-)AG system for anionic amino-acid uptake is sensitive to the proliferative status of the cell population and that, in particular, its transport activity is stimulated by the establishment of proliferative quiescence.
在NIH-3T3细胞中研究了阴离子氨基酸转运与细胞群体增殖状态之间的关系。通过测定生长速率商和胸苷掺入量验证的增殖静止与L-天冬氨酸流入量的显著增加有关。血清饥饿7-10天后，L-天冬氨酸的初始流入量相对于生长细胞中测定的转运活性增加了8-10倍。生长细胞和静止细胞中L-天冬氨酸流入的操作特性相似；特别是，阴离子氨基酸的流入主要依赖于Na(+)，并被过量的L-谷氨酸和D-天冬氨酸完全抑制，但不被D-谷氨酸抑制。这些特征表明，在这两种情况下，天冬氨酸的摄取都是通过X(-)AG系统进行的。与静止相关的天冬氨酸转运增加是渐进的，对蛋白质合成抑制敏感，并且归因于转运系统X(-)AG的最大容量增强。在血清饥饿细胞的培养基中恢复血清浓度会导致天冬氨酸转运减少，在对应于G1/S晚期时达到最大。得出的结论是，用于摄取阴离子氨基酸的X(-)AG系统对细胞群体的增殖状态敏感，特别是其转运活性受到增殖静止状态的刺激。
