Polyamine uptake in cultured astrocytes:: Characterization and modulation by protein kinases
Polyamine uptake in cultured astrocytes:: Characterization and modulation by protein kinases
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DOI：
10.1046/j.1471-4159.2000.0751917.x
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发表时间：
2000-11-01
影响因子：
4.7
通讯作者：
Rodríguez-Alvarez, J
中科院分区：
文献类型：
--
作者：
Dot, J;Lluch, M;Rodríguez-Alvarez, J
脑内多胺转运系统的性质和调控尚不清楚。本研究首次表明，在小脑星形胶质细胞中存在多胺转运系统，并表明多胺摄取是由腐胺、精胺和亚精胺（K-m分别为3.2、1.2和1.8 μ M）的单一、饱和高亲和力转运系统介导的。虽然氯化胆碱取代NaCl会减少腐胺、精胺和亚精胺的摄取，但在小脑星形胶质细胞中，多胺的运输似乎不像在Na+和胆碱存在时那样由Naf共同运输介导，多胺的摄取远低于在蔗糖基培养基中测量。另一方面，瓦巴因、gramicidin（一种Na+离子载体）和iononomycin（一种Ca2+离子载体）对多胺摄取产生强烈的抑制作用，表明膜电位可能在星形胶质细胞多胺摄取系统的功能中起重要作用。此外，抑制蛋白激酶C可增强多胺摄取，而用磷酸酯刺激蛋白激酶C可抑制多胺摄取。另外，酪氨酸激酶抑制剂染料木素引起摄取的显著减少。环amp依赖性蛋白激酶的抑制剂和激活剂或Ca2+/钙调素依赖性蛋白激酶II被KN-62抑制时，对多胺摄取没有影响。提示小脑星形胶质细胞多胺摄取系统可能受蛋白激酶C和酪氨酸激酶活性的调控。
The properties and regulation of the polyamine transport system in brain are still poorly understood. The present study shows, for the first time, the existence of a polyamine transport system in cerebellar astrocytes and suggests that polyamine uptake is mediated by a single and saturable high-affinity transport system for putrescine, spermine, and spermidine (K-m = 3.2, 1.2, and 1.8 mu M, respectively). Although substitution of NaCl by choline chloride produced a decrease in the putrescine, spermine, and spermidine uptake, it seems that polyamine transport in cerebellar astrocytes is not mediated by an Naf cotransport as in the presence of Na+ and cholinium, polyamine uptake was much lower than when measured in a sucrose-based medium. On the other hand, ouabain, gramicidin (a Na+ ionophore), and ionomycin (a Ca2+ ionophore) produced a strong inhibition of polyamine uptake, suggesting that membrane potential could have an important role in the functioning of the astroglial polyamine uptake system. Moreover, protein kinase C inhibition produced an enhancement of polyamine uptake, whereas stimulation of protein kinase C with phorbol esters inhibited polyamine uptake. Alternatively, the tyrosine kinase inhibitor genistein caused a marked reduction in the uptake. No effects on polyamine uptake were observed with inhibitors and activators of cyclic AMP-dependent protein kinase or when Ca2+/calmodulin-dependent protein kinase II was inhibited with KN-62. These results suggest that the polyamine uptake system in cerebellar astrocytes could be modulated by protein kinase C and tyrosine kinase activities.