Division of Gastroenterology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Dev Cell. 2012 Sep 11;23(3):573-86. doi: 10.1016/j.devcel.2012.08.002.
The glycosphingolipid GM1 binds cholera toxin (CT) on host cells and carries it retrograde from the plasma membrane (PM) through endosomes, the trans-Golgi (TGN), and the endoplasmic reticulum (ER) to induce toxicity. To elucidate how a membrane lipid can specify trafficking in these pathways, we synthesized GM1 isoforms with alternate ceramide domains and imaged their trafficking in live cells. Only GM1 with unsaturated acyl chains sorted efficiently from PM to TGN and ER. Toxin binding, which effectively crosslinks GM1 lipids, was dispensable, but membrane cholesterol and the lipid raft-associated proteins actin and flotillin were required. The results implicate a protein-dependent mechanism of lipid sorting by ceramide structure and provide a molecular explanation for the diversity and specificity of retrograde trafficking by CT in host cells.
神经节苷脂 GM1 与宿主细胞上的霍乱毒素（CT）结合，并将其从质膜（PM）通过内体、反式高尔基体（TGN）和内质网（ER）逆行携带，以诱导毒性。为了阐明膜脂如何在这些途径中指定运输，我们合成了具有不同神经酰胺结构域的 GM1 异构体，并在活细胞中对其运输进行了成像。只有具有不饱和酰基链的 GM1 才能有效地从 PM 分拣到 TGN 和 ER。毒素结合有效地交联 GM1 脂质，但膜胆固醇和与脂筏相关的蛋白质肌动蛋白和 flotillin 是必需的。这些结果表明，神经酰胺结构的蛋白依赖性脂质分拣机制，并为 CT 在宿主细胞中的逆行运输的多样性和特异性提供了分子解释。
