Graduate School of Biomedical Engineering, Tohoku University, Miyagi, Japan; Department of Molecular Biophysics and Biochemistry, New Haven, Yale University, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA.
Graduate School of Engineering, Department of Finemechanics, Tohoku University, Miyagi, Japan; Graduate School of Biomedical Engineering, Tohoku University, Miyagi, Japan.
Biochem Biophys Res Commun. 2024 Apr 30;706:149762. doi: 10.1016/j.bbrc.2024.149762. Epub 2024 Mar 7.
Revealing the mechanisms of glucose transport is crucial for studying pathological diseases caused by glucose toxicities. Numerous studies have revealed molecular functions involved in glucose transport in the nematode Caenorhabditis elegans, a commonly used model organism. However, the behavior of glucose in the intestinal lumen-to-cell remains elusive. To address that, we evaluated the diffusion coefficient of glucose in the intestinal apical brush border of C. elegans by using fluorescent glucose and fluorescence recovery after photobleaching. Fluorescent glucose taken in the intestine of worms accumulates in the apical brush border, and its diffusion coefficient of ∼10 cm/s is two orders of magnitude slower than that in bulk. This result indicates that the intestinal brush border is a viscous layer. ERM-1 point mutations at the phosphorylation site, which shorten the microvilli length, did not significantly affect the diffusion coefficient of fluorescent glucose in the brush border. Our findings imply that glucose enrichment is dominantly maintained by the viscous layer composed of the glycocalyx and molecular complexes on the apical surface.
揭示葡萄糖转运的机制对于研究葡萄糖毒性引起的病理疾病至关重要。大量研究揭示了线虫秀丽隐杆线虫中参与葡萄糖转运的分子功能，秀丽隐杆线虫是一种常用的模式生物。然而，肠道腔到细胞内的葡萄糖行为仍然难以捉摸。为了解决这个问题，我们通过使用荧光葡萄糖和光漂白后荧光恢复，评估了葡萄糖在秀丽隐杆线虫肠道顶端刷状边界的扩散系数。在蠕虫肠道中摄取的荧光葡萄糖积累在顶端刷状边界，其扩散系数约为 10cm/s，比在整体中慢两个数量级。这一结果表明，肠道刷状边界是一个粘性层。在磷酸化位点发生 ERM-1 点突变，缩短微绒毛长度，并没有显著影响刷状边界中荧光葡萄糖的扩散系数。我们的发现表明，葡萄糖的富集主要是由顶端表面的糖萼和分子复合物组成的粘性层维持的。
