Veyhl-Wichmann Maike, Friedrich Alexandra, Vernaleken Alexandra, Singh Smriti, Kipp Helmut, Gorboulev Valentin, Keller Thorsten, Chintalapati Chakravarthi, Pipkorn Rüdiger, Pastor-Anglada Marçal, Groll Jürgen, Koepsell Hermann
Institute of Anatomy and Cell Biology, University Würzburg, Germany (M.V., A.V., H.Ki, V.G., C.C., H.Ko.); Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Germany (S.S., J.G.); Leibnitz Institute for Interactive Materials, Rheinisch-Westfälische Technische Hochschule, University Aachen, Germany (S.S.); German Cancer Research Center, Heidelberg, Germany (R.P.); Department of Biochemistry and Molecular Biology, Institute of Biomedicine, University Barcelona & CIBER EHD, Barcelona, Spain (M.P.); and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University Würzburg, Germany (A.F., T.K., H.Ko).
Institute of Anatomy and Cell Biology, University Würzburg, Germany (M.V., A.V., H.Ki, V.G., C.C., H.Ko.); Department of Functional Materials in Medicine and Dentistry, University Hospital Würzburg, Germany (S.S., J.G.); Leibnitz Institute for Interactive Materials, Rheinisch-Westfälische Technische Hochschule, University Aachen, Germany (S.S.); German Cancer Research Center, Heidelberg, Germany (R.P.); Department of Biochemistry and Molecular Biology, Institute of Biomedicine, University Barcelona & CIBER EHD, Barcelona, Spain (M.P.); and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University Würzburg, Germany (A.F., T.K., H.Ko)
Mol Pharmacol. 2016 Jan;89(1):118-32. doi: 10.1124/mol.115.101162. Epub 2015 Oct 13.
Cellular uptake adapts rapidly to physiologic demands by changing transporter abundance in the plasma membrane. The human gene RSC1A1 codes for a 67-kDa protein named RS1 that has been shown to induce downregulation of the sodium-D-glucose cotransporter 1 (SGLT1) and of the concentrative nucleoside transporter 1 (CNT1) in the plasma membrane by blocking exocytosis at the Golgi. Injecting RS1 fragments into Xenopus laevis oocytes expressing SGLT1 or CNT1 and measuring the expressed uptake of α-methylglucoside or uridine 1 hour later, we identified a RS1 domain (RS1-Reg) containing multiple predicted phosphorylation sites that is responsible for this post-translational downregulation of SGLT1 and CNT1. Dependent on phosphorylation, RS1-Reg blocks the release of SGLT1-containing vesicles from the Golgi in a glucose-dependent manner or glucose-independent release of CNT1-containing vesicles. We showed that upregulation of SGLT1 in the small intestine after glucose ingestion is promoted by glucose-dependent disinhibition of the RS1-Reg-blocked exocytotic pathway of SGLT1 between meals. Mimicking phosphorylation of RS1-Reg, we obtained a RS1-Reg variant that downregulates SGLT1 in the brush-border membrane at high luminal glucose concentration. Because RS1 mediates short-term regulation of various transporters, we propose that the RS1-Reg-navigated transporter release from Golgi represents a basic regulatory mechanism of general importance, which implies the existence of receptor proteins that recognize different phosphorylated forms of RS1-Reg and of complex transporter-specific sorting in the trans-Golgi. RS1-Reg-derived peptides that downregulate SGLT1 at high intracellular glucose concentrations may be used for downregulation of glucose absorption in small intestine, which has been proposed as strategy for treatment of type 2 diabetes.
细胞摄取通过改变质膜中转运蛋白的丰度迅速适应生理需求。人类基因RSC1A1编码一种名为RS1的67 kDa蛋白质，该蛋白质已被证明可通过阻断高尔基体的胞吐作用来诱导质膜中钠 - D - 葡萄糖共转运蛋白1（SGLT1）和浓缩核苷转运蛋白1（CNT1）的下调。将RS1片段注射到表达SGLT1或CNT1的非洲爪蟾卵母细胞中，并在1小时后测量α - 甲基葡萄糖苷或尿苷的表达摄取量，我们鉴定出一个包含多个预测磷酸化位点的RS1结构域（RS1 - Reg），该结构域负责SGLT１和CNT1的这种翻译后下调。依赖于磷酸化，RS1 - Reg以葡萄糖依赖的方式阻断含SGLT1囊泡从高尔基体的释放，或葡萄糖不依赖的方式阻断含CNT1囊泡的释放。我们发现，餐后葡萄糖依赖性解除对RS1 - Reg阻断的SGLT1胞吐途径的抑制作用，可促进葡萄糖摄入后小肠中SGLT1的上调。模拟RS1 - Reg的磷酸化，我们获得了一种RS1 - Reg变体，该变体在高管腔葡萄糖浓度下可下调刷状缘膜中的SGLT1。由于RS1介导各种转运蛋白的短期调节，我们提出，RS1 - Reg引导的转运蛋白从高尔基体的释放代表了一种具有普遍重要性的基本调节机制，这意味着存在识别RS1 - Reg不同磷酸化形式的受体蛋白，以及在反式高尔基体中存在复杂的转运蛋白特异性分选。在高细胞内葡萄糖浓度下可下调SGLT1的RS1 - Reg衍生肽，可用于下调小肠中的葡萄糖吸收，这已被提议作为治疗2型糖尿病的策略。
