Istituto di Patologia Generale, Università degli Studi di Parma, Via Gramsci, 14, I-43100, Parma, Italy.
Amino Acids. 1996 Jun;11(2):247-55. doi: 10.1007/BF00813863.
The expression of wild type CFTR facilitates the efflux of neutral amino acids (Rotoli et al., Biochem. Biophys. Res. Commun. 204: 653-658, 1994); as a result, after an extensive depletion of intracellular amino acid pool obtained through an incubation in saline solution, the intracellular leucine levels were lower in murine C127 cells transfected with the wild type CF gene (C127 CFTRw/t) than in cells transfected with either mutant CF (C127 CFTRΔF508 cells) or mock vector only. No change in amino acid efflux was detected when C127 CFTRw/t and C127 CFTRw/t and C127 CFTRΔF508 cells were studied under conditions known to activate protein kinase A. Upon an incubation in Cl(-) free medium, a permeant analogue of cAMP caused a marked cell depolarization of C127 CFTRw/t cells but not of C127 CFTRΔF508 cells, thus showing a functional expression of CFTR protein in the former cell line. However, we found that, upon a Cl(-) free incubation and in the absence of exogenous cAMP, C127 CFTRw/t cells developed a marked hyperpolarization that was not detected in C127 CFTRΔF508 cells. It is concluded that the expression of normal CFTR accelerates amino acid efflux and enhances cell hyperpolarization in Cl(-) free media; both these effects appear to be independent from PKA stimulation of CFTR.
野生型 CFTR 的表达促进了中性氨基酸的外排（Rotoli 等人，生物化学。生物物理。Res.Commun. 204:653-658,1994）；因此，在用盐水孵育使细胞内氨基酸池大量耗尽后，转染野生型 CF 基因（C127 CFTRw/t）的鼠 C127 细胞内亮氨酸水平低于转染突变型 CF（C127 CFTRΔF508 细胞）或空载载体的细胞（C127 CFTRΔF508 细胞）。当在已知激活蛋白激酶 A 的条件下研究 C127 CFTRw/t 和 C127 CFTRw/t 和 C127 CFTRΔF508 细胞时，未检测到氨基酸外排的变化。在用 Cl(-) 自由培养基孵育时，cAMP 的可渗透类似物引起 C127 CFTRw/t 细胞的明显去极化，但 C127 CFTRΔF508 细胞没有，因此在前一种细胞系中显示 CFTR 蛋白的功能表达。然而，我们发现，在用 Cl(-) 自由孵育且没有外源性 cAMP 的情况下，C127 CFTRw/t 细胞发生了明显的超极化，而在 C127 CFTRΔF508 细胞中未检测到。结论是，正常 CFTR 的表达加速了氨基酸的外排，并增强了 Cl(-) 自由介质中的细胞超极化；这两种效应似乎都独立于 CFTR 的 PKA 刺激。
