Schulz Tobias, Schumacher Udo, Prehm Peter
Institute of Physiological Chemistry and Pathobiochemistry, Muenster University Hospital, D-48129 Muenster, Germany.
J Biol Chem. 2007 Jul 20;282(29):20999-1004. doi: 10.1074/jbc.M700915200. Epub 2007 May 31.
Hyaluronan must be exported from its site of synthesis, the inner side of plasma membrane, to the extracellular matrix. Here, we identified the multidrug-associated protein MRP5 as the principle hyaluronan exporter from fibroblasts. The expression of the MRP5 (ABC-C5) transporter was silenced in fibroblasts using RNA interference, and a dose-dependent inhibition of hyaluronan export was observed. Hyaluronan oligosaccharides introduced into the cytosol competed with the export of endogenously labeled hyaluronan and the MRP5 substrate fluorescein. Because cGMP is a physiological substrate of MRP5, the intracellular concentrations of cGMP were modulated by the drugs 3-isobutyl-1-methylxanthin, propentofyllin, L-NAME, zaprinast, and bromo-cGMP, and the effects on hyaluronan export were analyzed. Increasing the cGMP levels inhibited hyaluronan export and decreasing it afforded higher concentrations of zaprinast to inhibit the export. Thus, cGMP may be a physiological regulator of hyaluronan export at the level of the export MRP5.
透明质酸必须从其合成部位——质膜内侧转运至细胞外基质。在此，我们鉴定出多药相关蛋白MRP5是成纤维细胞中主要的透明质酸转运蛋白。利用RNA干扰技术使成纤维细胞中MRP5（ABC - C5）转运体的表达沉默，结果观察到透明质酸转运受到剂量依赖性抑制。导入细胞质的透明质酸寡糖与内源性标记的透明质酸以及MRP5底物荧光素的转运相互竞争。由于环磷酸鸟苷（cGMP）是MRP5的生理性底物，因此使用3 - 异丁基 - 1 - 甲基黄嘌呤、丙戊茶碱、L - 精氨酸甲酯（L - NAME）、扎普司特和溴化环磷酸鸟苷对细胞内cGMP浓度进行调节，并分析其对透明质酸转运的影响。提高cGMP水平会抑制透明质酸转运，而降低cGMP水平则使扎普司特浓度升高从而抑制转运。因此，cGMP可能是在MRP5转运水平上透明质酸转运的生理性调节因子。
