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首页> 外文期刊>Journal of Cellular Physiology >Contrasting effects of oncogene expression on two carrier-mediated systems internalizing folate compounds in Fisher rat 3T3 cells.
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Contrasting effects of oncogene expression on two carrier-mediated systems internalizing folate compounds in Fisher rat 3T3 cells.

机译：癌基因表达在两个截然不同的影响carrier-mediated系统内在叶酸化合物在费舍尔鼠3 t3细胞。

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Folate compound transport into Fisher rat 3T3 (FR3T3) cells at physiological pH occurs predominantly by an acid pH-dependent, mobile carrier system. However, influx of [(3)H]MTX by this system is 3-4-fold higher at pH 6 than at pH 7.5, the optimum for RFC-1-mediated folate compound transport. This acid pH dependency reflects an alteration of influx V(max) rather than of influx K(m) in these cells at different pH. Acid pH-dependent folate compound transport interacts effectively with MTX, 5lLCHO-folateH(4), 5lLCH(3)-folateH(4) and folic acid as permeants (influx Ki = 2.7-5.3 microM). The relative inhibition of influx of [(3)H]MTX by the organic anions, probenecid, and PO(4) was different than for RFC-1 mediated influx. The folate requirements for growth in culture of FR3T3 cells and cytotoxicity of MTX compared to L1210 cells reflects the interactions of these folate compounds with acid pH-dependent folate transport. 5lLCHO-folateH(4) and PO(4) act as exchange anions for this system but their transpositioning has variable effects on transport. 5lLCHO-folateH(4) inhibits influx (decelerative equilibrium exchange) but stimulates efflux of [(3)H]MTX (accelerative equilibrium exchange) while PO(4) inhibits efflux. In FR3T3 cells transfected with cmyc and Hras, influx V(max) for [(3)H]MTX is downregulated 4-fold and 9-fold, respectively. At the same time, RFC-1 expression, which is detectable in FR3T3 cells at the level of its mRNA and RFC-1 mediated folate compound transport, is increased 3-5-fold in these transfectants. The increase in RFC-1 expression in FR3T3Hras cells appears to result from a higher rate of transcription of the gene in these cells as determined by a luciferase reporter gene assay of RFC-1 promoter activity. This downregulation of the acid pH dependent system and concomitant upregulation of the RFC-1 mediated system markedly altered pH dependency for influx of [(3)H]MTX in these transfectants compared to that seen in untransfected cells. We conclude that the major route for internalization at a physiological pH of folate compounds in FR3T3 cells is by an acid pH-dependent carrier-mediated system independent of RFC-1 expression and is downregulated by oncogene expression. Copyright 2000 Wiley-Liss, Inc.
机译：叶酸的复合运输到费舍尔鼠3 t3(FR3T3)细胞在生理pH值主要由酸pH-dependent、移动载体系统。这个系统是3-4-fold比在pH值更高的pH值67.5最优RFC-1-mediated叶酸复合运输。反映了V (max),而涌入的变更比K (m)涌入这些细胞在不同博士酸pH-dependent叶酸复合运输有效地与MTX相互作用,5 llch 5 llcho-folateh (4), (3) -folateH(4)和叶酸酸作为渗透的(Ki涌入= 2.7 -5.3 microM)。的相对抑制[(3)H] MTX的涌入有机阴离子、丙磺舒、PO (4)不同的比RFC-1介导涌入。叶酸的文化需求增长FR3T3细胞和细胞毒性的MTX相比L1210细胞反映的相互作用叶酸化合物与酸pH-dependent叶酸交通工具。这个系统,但他们的交换阴离子换位变量的影响交通工具。但(decelerative均衡交换)刺激[(3)H] MTX的流出(加速的平衡交换),(4)抑制流出。极品,涌入V (max) [(3) H] MTX分别下调4倍和9倍。同时,RFC-1表达式,它是FR3T3细胞中检测到的水平信使rna和RFC-1叶酸介导的化合物在这些交通工具,增加3-5-fold转染子。在FR3T3Hras细胞似乎从一个结果更高的基因的转录细胞的荧光素酶报告基因RFC-1子活动的分析。downregulation酸性pH值依赖的系统和伴随upregulation RFC-1介导系统显著改变pH值的依赖((3) H)流入MTX在这些转染子而在untransfected细胞。得出结论,内部化的主要途径叶酸化合物的生理pH值由酸pH-dependent FR3T3细胞RFC-1 carrier-mediated系统无关表达和由癌基因表达下调表达式。

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