Veyhl M, Wagner C A, Gorboulev V, Schmitt B M, Lang F, Koepsell H
Institut für Anatomie und Zellbiologie, Bayerische Julius-Maximilians Universität, Koellikerstr. 6, D-97070 Würzburg, Germany.
J Membr Biol. 2003 Nov 1;196(1):71-81. doi: 10.1007/s00232-003-0626-y.
We have previously shown that the regulatory protein RS1, cloned from pig, rabbit and human (RSC1A1), is localized intracellularly and inhibits the transcription of the Na(+)- D-glucose cotransporter SGLT1 in LLC-PK(1) cells. We also reported that transport activities of human SGLT1 (hSGLT1) and human organic cation transporter hOCT2 expressed in Xenopus oocytes were decreased upon co-expression of human RS1 (hRS1). The present paper indicates that the glucose transporter GLUT1 and the peptide transporter PEPT1 are not influenced by hRS1. Voltage-clamp experiments in oocytes expressing hSGLT1 demonstrated that hRS1 reduced the maximal substrate-induced currents but did not change substrate activation, membrane potential dependence, Na(+) dependence or substrate selectivity of hSGLT1. Co-expression experiments with a dominant-negative dynamin mutant showed that the posttranslational inhibition of hSGLT1 by hRS1 was dependent on the function of dynamin. Finally, we observed that hRS1 changed the short-term effect of protein kinase C (PKC) on hSGLT1. Whereas the PKC activators phorbol-12-myristate-13-acetate (PMA) and sn-1,2-dioctanoyl glycerol (DOG) increased alpha-methyl glucose (AMG) uptake expressed by hSGLT1 alone as described earlier, PMA and DOG decreased AMG uptake mediated by hSGLT1 when hRS1 was co-expressed. Taken together, these data indicate that hRS1 modulates dynamin-dependent trafficking of intracellular vesicles containing hSGLT1 in Xenopus oocytes, and modulates PKC-dependent short-term regulation of this transporter.
我们先前已表明，从猪、兔和人类中克隆出的调节蛋白RS1（RSC1A1）定位于细胞内，并抑制LLC-PK(1)细胞中钠-葡萄糖共转运蛋白SGLT1的转录。我们还报道，在非洲爪蟾卵母细胞中共同表达人类RS1（hRS1）时，人类SGLT1（hSGLT1）和人类有机阳离子转运体hOCT2的转运活性会降低。本文表明葡萄糖转运体GLUT1和肽转运体PEPT1不受hRS1影响。在表达hSGLT1的卵母细胞中进行的电压钳实验表明，hRS1降低了最大底物诱导电流，但未改变hSGLT1的底物激活、膜电位依赖性、钠依赖性或底物选择性。与显性负性发动蛋白突变体的共同表达实验表明，hRS1对hSGLT1的翻译后抑制依赖于发动蛋白的功能。最后，我们观察到hRS1改变了蛋白激酶C（PKC）对hSGLT1的短期作用。如前所述，PKC激活剂佛波醇-12-肉豆蔻酸酯-13-乙酸酯（PMA）和sn-1,2-二辛酰甘油（DOG）单独增加了hSGLT1介导的α-甲基葡萄糖（AMG）摄取，而当共同表达hRS1时，PMA和DOG降低了hSGLT1介导的AMG摄取。综上所述，这些数据表明hRS1调节非洲爪蟾卵母细胞中含有hSGLT1的细胞内囊泡的发动蛋白依赖性运输，并调节该转运体的PKC依赖性短期调节。
