Dawson W D, Cook J S
University of Tennessee-Oak Ridge Graduate School of Biomedical Sciences 37831.
Prog Clin Biol Res. 1988;258:121-33.
Confluent, nongrowing renal epithelial cells, LLC-PK1, have a low rate of Na+-dependent (A-system) amino acid transport. Following a brief period of amino acid and serum deprivation, but with glucose provided as an energy source, such cells respond to the tumor promoter TPA with a brief enhancement of A-system activity that returns to control levels within 10-20 min. The response is followed some 30 min later by a large and prolonged elevation of transport activity (delayed response). The responses may be related to an increased amino acid requirement in mitogenized cells. The initial transport response appears to be the consequence of a protein kinase C-dependent phosphorylation event, phosphorylating either a regulator or the transporter itself, while the delayed response is dependent on the synthesis of new protein. The delayed transport response may also be dependent upon an early phosphorylation event, although apparently less directly than the early transport response. Several candidate proteins that might be involved in the regulation of the response(s) may be seen when electrophoretically separated cell proteins are examined for 32P or [35S]methionine incorporation after TPA treatment.
汇合的、不生长的肾上皮细胞LLC-PK1，其依赖钠离子的（A系统）氨基酸转运速率较低。在短暂的氨基酸和血清剥夺期，但以葡萄糖作为能量来源的情况下，这些细胞对肿瘤启动子佛波酯（TPA）的反应是A系统活性短暂增强，并在10 - 20分钟内恢复到对照水平。大约30分钟后，会出现运输活性的大幅且持续升高（延迟反应）。这些反应可能与有丝分裂细胞中氨基酸需求增加有关。最初的运输反应似乎是蛋白激酶C依赖性磷酸化事件的结果，该事件使调节因子或转运体本身磷酸化，而延迟反应则依赖于新蛋白质的合成。延迟的运输反应可能也依赖于早期的磷酸化事件，尽管显然不如早期运输反应直接。当在TPA处理后检查电泳分离的细胞蛋白中32P或[35S]甲硫氨酸的掺入情况时，可能会看到几种可能参与反应调节的候选蛋白。
