Millhorn D E, Conforti L, Beitner-Johnson D, Zhu W, Raymond R, Filisko T, Kobayashi S, Peng M, Genter M B
Department of Molecular and Cellular Physiology, College of Medicine, University of Cincinnati, Ohio, USA.
Adv Exp Med Biol. 1996;410:135-42. doi: 10.1007/978-1-4615-5891-0_20.
We have shown that the PC12 cell line is an excellent model system for investigations of the molecular and cellular processes involved in O2-chemosensitivity. We have identified an O2-sensitive K channel in this cell line that mediates membrane depolarization, an increase in intracellular free Ca2+, and dopamine release during hypoxia. We also presented evidence which shows that expression of the gene for tyrosine hydroxylase, the rate-limiting enzyme in dopamine biosynthesis, is stimulated by reduced O2 tension in PC12 and type I carotid body cells. In addition, we have successfully identified the DNA sequences and trans-acting protein factors that regulate transcription of the TH gene during hypoxia. The mechanisms by which a reduction in O2 tension is transduced into alter cell function including increased gene expression remain unknown. Unpublished results from our laboratory show that the increased TH gene expression during hypoxia does not require activation of the cAMP-PKA signal transduction pathway. We propose that the increase in intracellular free Ca2+ that occurs as a result of membrane depolarization might play an important role. Preliminary findings from our laboratory show that blockade of the voltage operated Ca2+ channel or chelation of intracellular Ca2+ prevent full activation of the TH gene during hypoxia.
我们已经证明，PC12细胞系是研究与O2化学敏感性相关的分子和细胞过程的优秀模型系统。我们在该细胞系中鉴定出一种对O2敏感的钾通道，它在缺氧期间介导膜去极化、细胞内游离Ca2+增加以及多巴胺释放。我们还提供了证据表明，在PC12和I型颈动脉体中，多巴胺生物合成的限速酶酪氨酸羟化酶的基因表达受到低氧张力的刺激。此外，我们已经成功鉴定出在缺氧期间调节TH基因转录的DNA序列和反式作用蛋白因子。低氧张力降低转化为改变细胞功能（包括基因表达增加）的机制仍然未知。我们实验室未发表的结果表明，缺氧期间TH基因表达的增加不需要cAMP-PKA信号转导途径的激活。我们认为，膜去极化导致的细胞内游离Ca2+增加可能起重要作用。我们实验室的初步研究结果表明，阻断电压门控Ca2+通道或螯合细胞内Ca2+可防止缺氧期间TH基因的完全激活。
